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Taken together, these studies support a mechanism for exopolysaccharide export across the outer membrane that is distinct from the Wza-mediated translocation observed in canonical capsular polysaccharide export systems.

Bioenergetic aspects of the translocation of macromolecules across bacterial membranes. Bacteria are extremely versatile in the sense that they have gained the ability to transport all three major classes of biopolymers through their cell envelope: These macromolecules are translocated across membranes in a large number of cellular processe. Controlled release and antibacterial activity of tetracycline hydrochloride-loaded bacterial cellulose composite membranes.

Bacterial cellulose BC is widely used in biomedical applications. In this study, we prepared an antibiotic drug tetracycline hydrochloride TCH -loaded bacterial cellulose BC composite membranes , and evaluated the drug release, antibacterial activity and biocompatibility. In vitro antibacterial assay demonstrate that the developed BC-TCH composites displayed excellent antibacterial activity solely associated with the loaded TCH drug.

These characteristics of BC-TCH composite membranes indicate that they may successfully serve as wound dressings and other medical biomaterials. Mechanisms and aplications of macromolecule translocation across membranes of eukaryotic cells by bacterial toxins.

The bacterial protein toxins endowed with the ability to translocate across the plasmatic membrane are often crucial virulence factors of pathogenic bacteria invading eukaryotic organisms. These toxins translocate either their own protein domains carrying toxic activity or can form pores transferring other substances like small ions, DNA, RNA or proteins.

By observing the translocation of these molecules together with other artificially prepared agents on synthetic membranes it allows detaile Impact of ionic liquids in aqueous solution on bacterial plasma membranes studied with molecular dynamics simulations.

The impact of five different imidazolium-based ionic liquids ILs diluted in water on the properties of a bacterial plasma membrane is investigated using molecular dynamics MD simulations.

The atomistic model of the membrane bilayer is designed to reproduce the lipid composition of the plasma membrane of Gram-negative Escherichia coli. Spontaneous insertion of cations into the membrane is observed in all ILs. In contrast, anions do not adsorb onto the membrane surface nor diffuse into the bilayer. Once inserted, cations are oriented in parallel to membrane lipids with cation alkyl tails embedded into the hydrophobic membrane core, while the imidazolium-ring remains mostly exposed to the solvent.

Such inserted cations are strongly associated with one to two phospholipids in the membrane. This cation induced lipid disorder also reduces the average membrane thickness.

This effect is not observed after TDMIM insertions due to the similar length of cation alkyl chain and the fatty acids of the lipids. This lipid-mimicking behavior of inserted TDMIM indicates a high membrane affinity of this cation that could lead to an enhanced accumulation of cations in the membrane over time.

Overall, the simulations reveal how cations are inserted into the bacterial membrane and how such insertions change its properties. Moreover, the different roles of cations and anions are highlighted and the fundamental. Biological membranes , formed primarily by the self-assembly of complex mixtures of phospholipids, provide a structured scaffold for compartmentalization and structural processes in living cells. The specific physical properties of phospholipid species present in a given membrane play a key role in mediating these processes.

Phosphatidylethanolamine PE , a zwitterionic lipid present in bacterial , yeast, and mammalian cell membranes , is exceptional. In addition to undergoing the standard lipid polymorphic transition between the gel and liquid-crystalline phase, it can also assume an unusual polymorphic state, the inverse hexagonal phase HII.

Divalent cations are among the factors that drive the formation of the HII phase, wherein the lipid molecules form stacked tubular structures by burying the hydrophilic head groups and exposing the hydrophobic tails to the bulk solvent. Most biological membranes contain a lipid species capable of forming the HII state suggesting that such lipid polymorphic structural states play an important role in structural biological processes such as membrane fusion.

An understanding of these basic interactions enhances our understanding of membrane dynamics and how membrane -mediated structural changes may occur in vivo.

NMR structural studies of the bacterial outer membrane protein OmpX in oriented lipid bilayer membranes. The beta-barrels found in the outer membranes of prokaryotic and eukaryotic organisms constitute an important functional class of proteins. Here we present solid-state NMR spectra of the bacterial outer membrane protein OmpX in oriented lipid bilayer membranes.

We show that OmpX is folded in both glass-supported oriented lipid bilayers and in lipid bicelles that can be magnetically oriented with the membrane plane parallel or perpendicular to the direction of the magnetic field. The presence of resolved peaks in these spectra demonstrates that OmpX undergoes rotational diffusion around an axis perpendicular to the membrane surface.

A tightly hydrogen-bonded domain of OmpX resists exchange with D2O for days and is assigned to the transmembrane beta-barrel, while peaks at isotropic resonance frequencies that disappear rapidly in D2O are assigned to the extracellular and periplasmic loops. The data indicate that it will be possible to obtain site-specific resonance assignments and to determine the structure, tilt, and rotation of OmpX in membranes using the solid-state NMR methods that are currently being applied to alpha-helical membrane proteins.

Discovery of an archetypal protein transport system in bacterial outer membranes. Bacteria have mechanisms to export proteins for diverse purposes, including colonization of hosts and pathogenesis.

A small number of archetypal bacterial secretion machines have been found in several groups of bacteria and mediate a fundamentally distinct secretion process. Perhaps erroneously, proteins called 'autotransporters' have long been thought to be one of these protein secretion systems. Mounting evidence suggests that autotransporters might be substrates to be secreted, not an autonomous transporter system. We have discovered a new translocation and assembly module TAM that promotes efficient secretion of autotransporters in proteobacteria.

Functional analysis of the TAM in Citrobacter rodentium, Salmonella enterica and Escherichia coli showed that it consists of an Ompfamily protein, TamA, in the outer membrane and TamB in the inner membrane of diverse bacterial species.

The discovery of the TAM provides a new target for the development of therapies to inhibit colonization by bacterial pathogens. Reconstitution of a nanomachine driving the assembly of proteins into bacterial outer membranes.

In biological membranes , various protein secretion devices function as nanomachines, and measuring the internal movements of their component parts is a major technological challenge. The translocation assembly module the TAM is a nanomachine required for virulence of bacterial pathogens.

Here, we show that dynamic movements within the TamA component of the TAM are initiated in the presence of a substrate protein, Ag43, and that these movements recapitulate an initial stage in membrane protein assembly. The reconstituted system provides a powerful new means to study molecular movements in biological membranes , and the technology is widely applicable to studying the dynamics of diverse cellular nanomachines. Biofilm formation on contact surfaces contributes to persistence of foodborne pathogens all along the food and feed chain.

The specific physiological features of bacterial cells embedded in biofilms contribute to their high tolerance to environmental stresses, including the action of antimicrobial compounds. As membrane lipid adaptation is a vital facet of bacterial response when cells are submitted to harsh or unstable conditions, we focused here on membrane fatty acid composition of biofilm cells as compared to their free-growing counterparts.

Pathogenic bacteria Staphylococcus aureus, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella Typhimurium were cultivated in planktonic or biofilm states and membrane fatty acid analyses were performed on whole cells in both conditions. The percentage of saturated fatty acids increases in biofilm cells in all cases, with a concomitant decrease of branched-chain fatty acids for Gram-positive bacteria, or with a decrease in the sum of other fatty acids for Gram-negative bacteria.

We propose that increased membrane saturation in biofilm cells is an adaptive stress response that allows bacteria to limit exchanges, save energy, and survive. Reprogramming of membrane fluidity in biofilm cells might explain specific biofilm behavior including bacterial recalcitrance to biocide action. Treatment of tympanic membrane perforation using bacterial cellulose: Promising treatments for tympanic membrane perforation closure have been studied.

Therapies derived from tissue engineering probably eliminate the need for conventional surgery. Bacterial cellulose is presented as an alternative that is safe, biocompatible, and has low toxicity. To investigate the effect on healing of direct application of a bacterial cellulose graft on the tympanic membrane compared to the conventional approach with autologous fascia. Forty patients with tympanic membrane perforations secondary to chronic otitis media were included, and were randomly assigned to an experimental group 20 , treated with a bacterial cellulose graft BC and control group 20 , treated with autologous temporal fascia fascia.

We evaluated the surgical time, hospital stay, time of epithelialization and the rate of tympanic perforation closure. Hospital costs were compared. Bacterial cellulose grafts promoted the closure of the tympanic membrane perforations, and were demonstrated to be innovative, effective, safe, minimally invasive, efficacious and to have a very low cost.

Published by Elsevier Editora Ltda. Within a domain of radius approximately 25 nm, the receptor diffuses with a diffusion constant The purpose of the protein motion might be to facilitate transport of maltodextrins through the outer bacterial membrane Efficient quantification and characterization of bacterial outer membrane derived nano-particles with flow cytometric analysis.

There currently exists no efficient and easy method for size profiling and counting of membranous nano-scale particles, such as bacterial outer membrane vesicles OMVs. We present here a cost-effective and fast method capable of profiling and counting small sample volumes of nano-scale membranous vesicles with standard laboratory equipment without the need for any washing steps. OMV populations of different bacterial species are compared and even subpopulations of OMVs can be identified after a simple labelling procedure.

Counting is possible over three orders of magnitude without any changes to the protocol. Protein contaminations do not alter the described measurements. A cationic protein isolated from the seeds of the Moringa oleifera tree has been extensively studied for use in water treatment in developing countries and has been proposed for use in antimicrobial and therapeutic applications.

However, the molecular basis for the antimicrobial action of this peptide, Moringa oleifera cationic protein MOCP , has not been previously elucidated. We demonstrate here that a dominant mechanism of MOCP antimicrobial activity is membrane fusion. We used a combination of cryogenic electron microscopy cryo-EM and fluorescence assays to observe and study the kinetics of fusion of membranes in liposomes representing model microbial cells.

We also conducted cryo-EM experiments on E. Coarse-grained molecular dynamics simulations of membrane vesicles with MOCP molecules were used to elucidate steps in peptide adsorption, stalk formation, and fusion between membranes. Affinities and in-plane stress forces between glycopeptide antibiotics and biomimetic bacterial membranes. Full Text Available Understanding the molecular basis of interactions between antibiotics affecting bacterial cell wall biosynthesis and cellular membranes is important in rational drug design of new drugs to overcome resistance.

However, a precise understanding of how bacteriostatic antibiotics effect action often neglects the effect of biophysical forces involved following antibiotic-receptor binding events. We have employed a combination of a label-free binding biosensor surface plasmon resonance, SPR and a force biosensor in-plane stress cantilever, together with model membrane systems to study the complex interplay between glycopeptide antibiotics, their cognate ligands and different model membranes.

Binding affinities and kinetics of the antibiotics to these model membranes were influenced by electrostatic interactions with the different lipid backgrounds, in addition to ligand affinities. In addition, cantilever sensors coated with model membranes showed that planar surface stress changes were induced by glycopeptide antibiotics adsorption and caused compressive surface stress generation in a ligand-dependent manner.

Bacterial cellulose membrane as flexible substrate for organic light emitting devices. In order to achieve the necessary conductive properties indium tin oxide ITO thin films were deposited onto the membrane at room temperature using radio frequency r.

Resistivity, mobility and carrier concentration of deposited ITO films were 4. In order to demonstrate the feasibility of devices based on BC membranes three OLEDs with different substrates were produced: The observed OLED luminance ratio was: These preliminary results show clearly that the functionalized biopolymer, biodegradable, biocompatible bacterial cellulose membranes can be successfully used as substrate in flexible organic optoelectronic devices.

Adaptations of archaeal and bacterial membranes to variations in temperature, pH and pressure. The cytoplasmic membrane of a prokaryotic cell consists of a lipid bilayer or a monolayer that shields the cellular content from the environment. In addition, the membrane contains proteins that are responsible for transport of proteins and metabolites as well as for signalling and energy transduction. Maintenance of the functionality of the membrane during changing environmental conditions relies on the cell's potential to rapidly adjust the lipid composition of its membrane.

Despite the fundamental chemical differences between bacterial ester lipids and archaeal ether lipids, both types are functional under a wide range of environmental conditions. We here provide an overview of archaeal and bacterial strategies of changing the lipid compositions of their membranes.

Some molecular adjustments are unique for archaea or bacteria, whereas others are shared between the two domains. Strikingly, shared adjustments were predominantly observed near the growth boundaries of bacteria.

Here, we demonstrate that the presence of membrane spanning ether-lipids and methyl branches shows a striking relationship with the growth boundaries of archaea and bacteria. Recombinant Expression Screening of P.

However, much less is known about their structures and molecular mechanisms than for soluble proteins. Problems in expression, solubilization, purification, and crystallization cause bottlenecks in the characterization of TM proteins. This project addressed the need for improved methods for obtaining sufficient amounts of TM proteins for determining their structures and molecular mechanisms.

Results Plasmid clones were obtained that encode eighty-seven transmembrane proteins with varying physical characteristics, for example, the number of predicted transmembrane helices, molecular weight, and grand average hydrophobicity GRAVY. All the target proteins were from P. The relative expression levels of the transmembrane proteins were measured under several culture growth conditions. The use of E. In this study, proteins with a higher grand average hydrophobicity and more transmembrane helices were expressed less well than less hydrophobic proteins with fewer transmembrane helices.

Conclusions In this study, factors related to overall hydrophobicity and the number of predicted transmembrane helices correlated with the relative expression levels of the target proteins.

Identifying physical characteristics that correlate with protein expression might aid in selecting the "low hanging fruit", or proteins that can be expressed to sufficient levels using an E. The use of other expression strategies or host species might be needed for sufficient levels of expression of transmembrane proteins with other physical.

Electrochemical characterization of pore formation by bacterial protein toxins on hybrid supported membranes. The interaction of pore-forming streptolysin O SLO with biomimetic lipid membranes has been studied by electrochemical methods. Phosphatidylcholine lipid vesicles were deposited onto gold electrodes modified with supporting layers of hexyl thioctate HT or thioctic acid tri ethylene glycol ester TA-TEGE , and integrity and permeability of the resulting membranes were characterized by cyclic voltammetry and impedance spectroscopy.

Both positively and negatively charged electrochemical probes, potassium ferrocyanide, hexaammineruthenium III chloride, and ferrocene carboxylic acid FCA , were employed to evaluate their suitability to probe the membrane permeability properties, with FCA exhibiting ideal behavior and thus employed throughout the work.

The interaction of SLO with preformed supported lipid membranes was also investigated, and much lower response was observed, suggesting a different extent of membrane -toxin interactions on such an interface. Nonionic surfactant Triton was found to disrupt the vesicle structure but could not completely remove a preformed membrane to fully restore the electrode response. The information reported here offers some unique insight into toxin-surface interactions on a hybrid membrane , facilitating the development of electrochemically based sensing platforms for detecting trace amounts of bacterial toxins via the perforation process.

Bacterial origin of a mitochondrial outer membrane protein translocase: Mitochondria are of bacterial ancestry and have to import most of their proteins from the cytosol. This process is mediated by Tom40, an essential protein that forms the protein-translocating pore in the outer mitochondrial membrane. Tom40 is conserved in virtually all eukaryotes, but its evolutionary origin is unclear because bacterial orthologues have not been identified so far.

Recently, it was shown that the parasitic protozoon Trypanosoma brucei lacks a conventional Tom40 and instead employs the archaic translocase of the outer mitochondrial membrane ATOM , a protein that shows similarities to both eukaryotic Tom40 and bacterial protein translocases of the Omp85 family. Here we present electrophysiological single channel data showing that ATOM forms a hydrophilic pore of large conductance and high open probability. Moreover, ATOM channels exhibit a preference for the passage of cationic molecules consistent with the idea that it may translocate unfolded proteins targeted by positively charged N-terminal presequences.

This is further supported by the fact that the addition of a presequence peptide induces transient pore closure. An in-depth comparison of these single channel properties with those of other protein translocases reveals that ATOM closely resembles bacterial -type protein export channels rather than eukaryotic Tom Our results support the idea that ATOM represents an evolutionary intermediate between a bacterial Omplike protein export machinery and the conventional Tom40 that is found in mitochondria of other eukaryotes.

Guanidino groups greatly enhance the action of antimicrobial peptidomimetics against bacterial cytoplasmic membranes. Antimicrobial peptides or their synthetic mimics are a promising class of potential new antibiotics. Herein we assess the effect of the type of cationic side chain i. We found guanidino group-containing chimeras Surface physical chemistry properties in coated bacterial cellulose membranes with calcium phosphate. Bacterial cellulose has become established as a new biomaterial, and it can be used for medical applications.

In addition, it has called attention due to the increasing interest in tissue engineering materials for wound care. In this work, the bacterial cellulose fermentation process was modified by the addition of chondroitin sulfate to the culture medium before the inoculation of the bacteria.

The biomimetic process with heterogeneous calcium phosphate precipitation of biological interest was studied for the guided regeneration purposes on bacterial cellulose.

XTT results concluded that these materials did not affect significantly in the cell viability, being non-cytotoxic. Thus, it was produced one biomaterial with the surface charge changes for calcium phosphate deposition, besides different wettability which builds new membranes for Guided Tissue Regeneration.

Full Text Available Human amniotic membrane is considered a promising allograft material for the treatment of ocular surface reconstruction, burns, and other skin defects. In order to avoid the transmission of any diseases, grafts should be perfectly sterile. Twenty-five amniotic sacs were collected to determine the microbiological quality of human amniotic membrane , to analyze the radiation sensitivity pattern of the microorganism, and to detect the radiation decimal reduction dose D10 values.

All the samples were found to be contaminated, and the bioburden was ranged from 3. The results depict gradual decline in bioburden with incline of radiation doses. The D10 values of the bacterial isolates were ranged from 0. To compare the differences, D10 values were also calculated by graphical evaluations of the data with two of the representative isolates of each bacterial species which showed no significant variations. Findings of this study indicate that lower radiation dose is quite satisfactory for the sterilization of amniotic membrane grafts.

Therefore, these findings would be helpful to predict the efficacy of radiation doses for the processing of amniotic membrane for various purposes. Human amniotic membrane is considered a promising allograft material for the treatment of ocular surface reconstruction, burns, and other skin defects. Predominant membrane localization is an essential feature of the bacterial signal recognition particle receptor. Strikingly, although FtsY requires membrane contact for functionality, cell fractionation studies have localized FtsY predominantly to the cytosolic fraction of Escherichia coli.

So far, the exact function of the soluble SR in E. Results In the current study we have determined the contribution of soluble FtsY to co-translational targeting in vitro and have re-analysed the localization of FtsY in vivo by fluorescence microscopy.

These data show that soluble FtsY does not contribute significantly to cotranslational targeting in E. In agreement with this observation, our in vivo analyses of FtsY localization in bacterial cells by fluorescence microscopy revealed that the vast majority of FtsY was localized to the inner membrane and that soluble FtsY constituted only a negligible species in vivo.

Our data show that the bacterial SR is. Secretion of bacterial lipoproteins: Bacterial lipoproteins are peripherally anchored membrane proteins that play a variety of roles in bacterial physiology and virulence in monoderm single membrane -enveloped, e.

After export of prolipoproteins through the cytoplasmic membrane , which occurs predominantly but not exclusively via the general secretory or Sec pathway, the proteins are lipid-modified at the cytoplasmic membrane in a multistep process that involves sequential modification of a cysteine residue and cleavage of the signal peptide by the signal II peptidase Lsp. In both monoderms and diderms, signal peptide processing is preceded by acylation with a diacylglycerol through preprolipoprotein diacylglycerol transferase Lgt.

In diderms but also some monoderms, lipoproteins are further modified with a third acyl chain through lipoprotein N-acyl transferase Lnt. Fully modified lipoproteins that are destined to be anchored in the inner leaflet of the outer membrane OM are selected, transported and inserted by the Lol lipoprotein outer membrane localization pathway machinery, which consists of the inner- membrane IM ABC transporter-like LolCDE complex, the periplasmic LolA chaperone and the OM LolB lipoprotein receptor.

Surface localization of lipoproteins in diderms is rare in most bacteria, with the exception of several spirochetal species. In the model spirochete Borrelia burgdorferi, surface lipoprotein secretion does not follow established sorting rules, but remains dependent on N-terminal peptide sequences.

Secretion through the outer membrane requires maintenance of lipoproteins in a translocation-competent unfolded conformation. Effects of structure on the interactions between five natural antimicrobial compounds and phospholipids of bacterial cell membrane on model monolayers. Monolayers composed of bacterial phospholipids were used as model membranes to study interactions of naturally occurring phenolic compounds 2,5-dihydroxybenzaldehyde, 2-hydroxymethoxybenzaldehyde and the plant essential oil compounds carvacrol, cinnamaldehyde, and geraniol, previously found to be Enriched glucose and dextrin mannitol-based media modulates fibroblast behavior on bacterial cellulose membranes.

Bacterial cellulose BC produced by Gluconacetobacter hansenii is a suitable biopolymer for biomedical applications. In order to modulate the properties of BC and expand its use as substrate for tissue engineering mainly in the form of biomembranes, glucose or dextrin were added into a BC fermentation mannitol-based medium BCGl and BCDe, respectively under static culture conditions.

SEM images showed effects on fiber density and porosity on both sides of the BC membranes. Both enriched media decreased the BET surface area, water holding capacity, and rehydration rate. L fibroblast cells were seeded on all BC-based membranes and evaluated in aspects of cell adhesion, proliferation and morphology. BCG1 membranes showed the highest biological performance and hold promise for the use in tissue engineering applications.

Production of bacterial cellulose membranes in a modified airlift bioreactor by Gluconacetobacter xylinus. In this study, a novel bioreactor for producing bacterial cellulose BC is proposed. Traditional BC production uses static culture conditions and produces a gelatinous membrane. The potential for using various types of bioreactor, including a stirred tank, conventional airlift, and modified airlift with a rectangular wire-mesh draft tube, in large-scale production has been investigated.

The BC obtained from these bioreactors is fibrous or in pellet form. Our proposed airlift bioreactor produces a membrane -type BC from Gluconacetobacter xylinus, the water-holding capacity of which is greater than that of cellulose types produced using static cultivation methods. The Young's modulus of the product can be manipulated by varying the number of net plates in the modified airlift bioreactor.

The BC membrane produced using the proposed bioreactor exhibits potential for practical application. Freestanding bacterial cellulose-graphene oxide composite membranes with high mechanical strength for selective ion permeation.

Graphene oxide GO based membranes have been widely applied in molecular separation based on the size exclusion effect of the nanochannels formed by stacked GO sheets.

Here, a freestanding composite membrane based on bacterial cellulose BC and GO is designed and prepared. Therefore, this novel composite membrane is considered to be a promising candidate in the applications of water purification, food industry, biomedicine, and pharmaceutical and fuel separation. Altering the thermal resistance of foodborne bacterial pathogens with an eggshell membrane waste by-product.

Eggshells from egg-breaking operations are a significant waste disposal problem. Thus, the development of value-added by-products from this waste would be welcomed by the industry. The ability of extracted eggshell membranes containing, several bacteriolytic enzymes i. Following exposure, membrane -free samples 1. Population reductions ranging from D-value reductions ranging from 0 LM to The effects of exposure pH, time, temperature, and organic load on membrane activity were also evaluated with Salmonella Typhimurium.

However, the presence of organic matter 0. These preliminary findings provide information on the potential use of extracted eggshell. A bilayer-couple model of bacterial outer membrane vesicle biogenesis. Gram-negative bacteria naturally produce outer membrane vesicles OMVs that arise through bulging and pinching off of the outer membrane.

OMVs have several biological functions for bacteria, most notably as trafficking vehicles for toxins, antimicrobials, and signaling molecules. While their biological roles are now appreciated, the mechanism of OMV formation has not been fully elucidated. We hypothesized that PQS stimulates OMV formation through direct interaction with the outer leaflet of the outer membrane. To test this hypothesis, we employed a red blood cell RBC model that has been used extensively to study small-molecule- membrane interactions.

Our results revealed that addition of PQS to RBCs induced membrane curvature, resulting in the formation of membrane spicules spikes , consistent with small molecules that are inserted stably into the outer leaflet of the membrane. Radiotracer experiments demonstrated that sufficient PQS was inserted into the membrane to account for this curvature and that curvature induction was specific to PQS structure.

These data suggest that a low rate of interleaflet flip-flop forces PQS to accumulate in and expand the outer leaflet relative to the inner leaflet, thus inducing membrane curvature. In support of PQS-mediated outer leaflet expansion, the PQS effect was antagonized by chlorpromazine, a molecule known to be preferentially inserted into the inner leaflet.

Based on these data, we propose a bilayer-couple model to describe P. Despite the ubiquity and importance of outer membrane vesicle OMV production in Gram-negative bacteria, the molecular details of OMV biogenesis are not fully understood. The membranes are based on blending bacterial nanocellulose pulp and Nafion abbreviated as BxNy, where x and y indicates the mass ratio of bacterial cellulose to Nafion.

It is found that the BxNy composite membranes with reinforced concrete-like structure show excellent mechanical and thermal stability regardless of annealing.

The water uptake plus area and volume swelling ratios are all decreased compared to Nafion membranes. The proton conductivities of pristine and annealed B1N9 are 0. Specifically, annealed B1N1 exhibited the lowest methanol permeability of 7. The performances of the pristine and annealed B1N7 reach a level as high as Translocation of dPNAG across the bacterial outer membrane is mediated by a tetratricopeptide repeat-containing outer membrane protein, PgaA. To understand the molecular basis of dPNAG translocation, we determined the crystal structure of the C-terminal transmembrane domain of PgaA residues Half of the interior surface of the barrel that lies parallel to the translocation pathway is electronegative, suggesting that the corresponding negatively charged residues may assist the secretion of the positively charged dPNAG polymer.

In vivo complementation assays in a pgaA deletion bacterial strain showed that a cluster of negatively charged residues proximal to the periplasm is necessary for biofilm formation. Biochemical analyses further revealed that the tetratricopeptide repeat domain of PgaA binds directly to the N-deacetylase PgaB and is critical for biofilm formation. Antimicrobial Nanoplexes meet Model Bacterial Membranes: Antimicrobial resistance to traditional antibiotics is a crucial challenge of medical research.

Oligonucleotide therapeutics, such as antisense or Transcription Factor Decoys TFDs , have the potential to circumvent current resistance mechanisms by acting on novel targets. However, their full translation into clinical application requires efficient delivery strategies and fundamental comprehension of their interaction with target bacterial cells. To address these points, we employed a novel cationic bolaamphiphile that binds TFDs with high affinity to form self-assembled complexes nanoplexes.

Confocal microscopy revealed that nanoplexes efficiently transfect bacterial cells, consistently with biological efficacy on animal models. To understand the factors affecting the delivery process, liposomes with varying compositions, taken as model synthetic bilayers, were challenged with nanoplexes and investigated with Scattering and Fluorescence techniques. Thanks to the combination of results on bacteria and synthetic membrane models we demonstrate for the first time that the prokaryotic-enriched anionic lipid Cardiolipin CL plays a key-role in the TFDs delivery to bacteria.

Moreover, we can hypothesize an overall TFD delivery mechanism, where bacterial membrane reorganization with permeability increase and release of the TFD from the nanoplexes are the main factors. These results will be of great benefit to boost the development of oligonucleotides-based antimicrobials of superior efficacy. Bacterial reaction centers purified with styrene maleic acid copolymer retain native membrane functional properties and display enhanced stability.

Antoinette; Jones, Michael R. Integral membrane proteins often present daunting challenges for biophysical characterization, a fundamental issue being how to select a surfactant that will optimally preserve the individual structure and functional properties of a given membrane protein.

Bacterial reaction centers offer a rare opp. Production and characterization of bacterial cellulose membranes with hyaluronic acid from chicken comb. The bacterial cellulose BC , from Gluconacetobacter hansenii, is a biofilm with a high degree of crystallinity that can be used for therapeutic purposes and as a candidate for healing wounds. Hyaluronic acid HA is a constitutive polysaccharide found in the extracellular matrix and is a material used in tissue engineering and scaffolding for tissue regeneration.

The structural characteristics, thermal stability and molar mass of hyaluronic acid from chicken comb were evaluated. Native membrane and polymeric composites were characterized with respect to their morphology and crystallinity.

The optimized process of extraction and purification of hyaluronic acid resulted in low molar mass hyaluronic acid with structural characteristics similar to the standard commercial hyaluronic acid. The membranes produced on the third day presented better incorporation of HA-SAB between cellulose microfiber, resulting in membranes with higher thermal stability, higher roughness and lower crystallinity. The biocompatiblily of bacterial cellulose and the importance of hyaluronic acid as a component of extracellular matrix qualify the polymeric composites as promising biomaterials for tissue engineering.

Full Text Available To improve the efficacy and safety of dural repair in neurosurgical procedures, a new dural material derived from bacterial cellulose BC was evaluated in a rabbit model with dural defects. We prepared artificial dura mater using bacterial cellulose which was incubated and fermented from Acetobacter xylinum.

The dural defects of the rabbit model were repaired with BC membranes. All surgeries were performed under sodium pentobarbital anesthesia, and all efforts were made to minimize suffering. All animals were humanely euthanized by intravenous injection of phenobarbitone, at each time point, after the operation. Then, the histocompatibility and inflammatory effects of BC were examined by histological examination, real-time fluorescent quantitative polymerase chain reaction PCR and Western Blot.

BC membranes evenly covered the surface of brain without adhesion. There were seldom inflammatory cells surrounding the membrane during the early postoperative period. BC can repair dural defects in rabbit and has a decreased inflammatory response compared to traditional materials.

However, the long-term effects need to be validated in larger animals. The participation of outer membrane proteins in the bacterial sensitivity to nanosilver. The presented study is to analyze the participation of outer membrane proteins of Gram- negative bacteria in sensitivity to silver nanomaterials.

The mechanism of interaction of silver with the bacterial cell is best described in this group of microorganisms. There are several theories regarding the effectiveness of antimicrobial ions and nanosilver, and at the indicated differences in the way they work. Outer membrane proteins of Gram-negative bacteria are involved in the procurement of silver from the environment and contribute to the development mechanisms of resistance to nanometals.

They are measurable parameter in the field of cell phenotypic response to the presence of Gram-negative bacteria in the environment silver nanoforms: During the very fast nanotechnology developing and introduction to the market products based on the nanosilver the bacterial answer to nanosilver is needed. Interspecies communication between pathogens and immune cells via bacterial membrane vesicles.

Full Text Available The production of extracellular vesicles is a universal mechanism for intercellular communication that is conserved across kingdoms. Prokaryotes secrete 50— nm membrane vesicles MVs in a manner that is regulated by environmental stress and is thought to promote survival. Since many types of host-derived stress are encountered during infection, this implies an important role for MV secretion in bacterial pathogenesis. Accordingly, MVs produced by gram-positive and gram-negative pathogens contain toxins, virulence factors, and other molecules that promote survival in the host.

However, recent studies have also shown that bacterial MVs are enriched for molecules that stimulate innate and adaptive immune responses. As an example, MVs may serve multiple, important roles in regulating the host response to Mycobacterium tuberculosis Mtb, an intracellular pathogen that infects lung macrophages and resides within modified phagosomes.

Previously, we demonstrated that Mtb secretes MVs during infection that may regulate infected and uninfected immune cells. We conclude that bacterial MVs serve dual and opposing roles in the activation of and defense against host immune responses to Mtb and other bacterial pathogens.

We also propose that MV secretion is a central mechanism for interspecies communication between bacteria and host cells during infection. Bacterial outer membrane vesicle biogenesis: First considered as a by-product of cell lysis, it soon became evident that OMVs are actively secreted from the outer membrane OM of Gram-negative bacteria.

However, OMVs may also comprise periplasmic, inner membrane , or cytoplasmic components. Since the shedding of substantial amounts of OM material represents a significant energy cost to the bacterial cell, OMV production must have some vital biological functions for Gram-negative bacteria. Indeed, intense research on that topic revealed that OMVs play important roles in bacterial physiology and pathogenesis, ranging from secretion and delivery of biomolecules for example, toxins, DNA, or quorum sensing molecules over stress response and biofilm formation to immunomodulation and adherence to host cells.

Only recently researchers have begun to elucidate the mechanistic aspects of OMV formation, but a general mechanism for the biogenesis of these vesicles is still lacking.

Here we review the findings and implications of our recent study published in Nature Communications Roier S, et al. This mechanism might not only have important pathophysiological roles in vivo, but also represents the first general mechanism of OMV formation applicable to all Gram-negative bacteria.

Outer membrane vesicle OMV release by Gram-negative bacteria has been observed and studied for decades. Full Text Available Aggregatibacter actinomycetemcomitans is a gram-negative opportunistic oral pathogen.

We have recently shown that this cytokine localizes to the cytoplasm of A. In this study, we characterized the interaction of A. The interacting protein, which we have designated bacterial interleukin receptor I BilRI, was identified through mass spectrometry and was found to be Pasteurellaceae specific.

Based on the results obtained using protein function prediction tools, this protein localizes to the outer membrane and contains a typical lipoprotein signal sequence. All six tested biofilm cultures of clinical A.

Moreover, proteinase K treatment of whole A. The protein was overexpressed in Escherichia coli in both the outer membrane -associated form and a soluble cytoplasmic form. When assessed using flow cytometry, the BilRI-overexpressing E. Overexpression of BilRI did not cause binding of a biotinylated negative control protein. Outer membrane vesicles OMVs are spherical nanostructures that are ubiquitously shed from gram-negative bacteria both in vitro and in vivo.

Recent findings revealed that OMVs, which contain diverse components derived from the parent bacterium, play an important role in communication with neighboring bacteria and the environment. Furthermore, nanoscale proteoliposomes decorated with pathogen-associated molecules attract considerable attention as a non-replicative carrier for vaccines and drug materials.

This review introduces recent advances in OMV biogenesis and discusses the roles of OMVs in the context of bacterial communication and virulence regulation.

It also describes the remarkable accomplishments in OMV engineering for diverse therapeutic applications. Influence of the physical state of the bacterial cell membrane upon the rate of respiration. Cell-free enzymes concerned in respiration and prepared from the same organisms are not inhibited by these salts, whereas these same enzymes tested in intact cells are. The physical state of the cell membrane appears to be a factor controlling its respiratory activity.

Explosive cell lysis as a mechanism for the biogenesis of bacterial membrane vesicles and biofilms. Many bacteria produce extracellular and surface-associated components such as membrane vesicles MVs , extracellular DNA and moonlighting cytosolic proteins for which the biogenesis and export pathways are not fully understood.

Here we show that the explosive cell lysis of a sub-population of cells accounts for the liberation of cytosolic content in Pseudomonas aeruginosa biofilms. Super-resolution microscopy reveals that explosive cell lysis also produces shattered membrane fragments that rapidly form MVs. A prophage endolysin encoded within the R- and F-pyocin gene cluster is essential for explosive cell lysis. Endolysin-deficient mutants are defective in MV production and biofilm development, consistent with a crucial role in the biogenesis of MVs and liberation of extracellular DNA and other biofilm matrix components.

Our findings reveal that explosive cell lysis, mediated through the activity of a cryptic prophage endolysin, acts as a mechanism for the production of bacterial MVs. Connective tissue and bacterial deposits on rubber dam sheet and ePTFE barrier membranes in guided periodontal tissue regeneration.

The aim of this study was to compare the connective tissue and bacterial deposits on rubber dam sheets and expanded polytetrafluoroethylene membranes used as barrier membranes in guided tissue regeneration for periodontal treatment.

Four to six weeks after the first operation, membranes were retrieved from the lesion sites and processed for scanning electron microscopy. The lesion-facing surfaces of membranes were examined for the presence of connective tissue and bacterial deposits. The differences between the numbers of fields and the distributions of connective tissue and bacteria on both types of membranes were analysed by the Chi-square test at the level of 0. The results showed a lot of fibroblasts with their secreted extracellular matrices, known as components of the connective tissue on rubber dam sheets and expanded polytetrafluoroethylene membranes.

Many bacterial forms including cocci, bacilli, filaments and spirochetes with the interbacterial matrices were identified. The total number of bacteria on rubber dam sheets was statistically less than that on expanded polytetrafluoroethylene membranes P tissue on both types of membranes suggests that the healing process under both types of membranes was also comparable.

Therefore, the rubber dam sheet might be used as a barrier membrane in guided tissue regeneration. Plasma membrane association of three classes of bacterial toxins is mediated by a basic-hydrophobic motif. Plasma membrane targeting is essential for the proper function of many bacterial toxins. A conserved fourhelical bundle membrane localization domain 4HBM was recently identified within three diverse families of toxins: When expressed in tissue culture cells or in yeast, GFP fusions to at least one 4HBM from each toxin family show significant peripheral membrane localization but with differing profiles.

Both in vivo expression and in vitro binding studies reveal that the ability of these domains to localize to the plasma membrane and bind negatively charged phospholipids requires a basic-hydrophobic motif formed by the L1 and L3 loops.

The different binding capacity of each 4HBM is defined by the hydrophobicity of an exposed residue within the motif. This study establishes that bacterial effectors utilize a normal host cell mechanism to locate the plasma membrane where they can then access their intracellular targets.

Probing the potential of apigenin liposomes in enhancing bacterial membrane perturbation and integrity loss. Along with discovery of new antibacterial agents, it is important to develop novel drug delivery systems to effectively deliver drugs within bacterial cells for enhanced therapeutic activity. Liposomes have been extensively investigated as pharmaceutical carriers for improvement of therapeutic index of antimicrobial agents.

The aim of this present study was to evaluate the antibacterial activity of free and liposomal formulation of apigenin, a plant based isoflavone and elucidate the mode of action. Distearoylphosphatidylcholine liposomes were prepared having nano-range particle size Antibacterial activity of apigenin and efficacy of liposome-mediated apigenin delivery were determined from minimum inhibitory concentration values. Interaction studies using electron microscopy revealed adherence and fusion of liposomal apigenin with the bacteria causing membrane perturbation through reactive oxygen species generation which was evaluated by epi-fluorescence microscopy and fluorescence activated cell sorting.

The interaction of apigenin liposomes with bacterial membrane increased intracellular drug concentration and thus, can be employed to deliver apigenin within cells to augment its antibacterial activity. Increased efficacy and hemocompatibility of this formulation paves way for future evaluation of underlying molecular mechanisms and in vivo testing for enhanced therapeutic effects. Long-distance delivery of bacterial virulence factors by Pseudomonas aeruginosa outer membrane vesicles.

Full Text Available Bacteria use a variety of secreted virulence factors to manipulate host cells, thereby causing significant morbidity and mortality. We report a mechanism for the long-distance delivery of multiple bacterial virulence factors, simultaneously and directly into the host cell cytoplasm, thus obviating the need for direct interaction of the pathogen with the host cell to cause cytotoxicity.

We show that outer membrane -derived vesicles OMV secreted by the opportunistic human pathogen Pseudomonas aeruginosa deliver multiple virulence factors, including beta-lactamase, alkaline phosphatase, hemolytic phospholipase C, and Cif, directly into the host cytoplasm via fusion of OMV with lipid rafts in the host plasma membrane. These virulence factors enter the cytoplasm of the host cell via N-WASP-mediated actin trafficking, where they rapidly distribute to specific subcellular locations to affect host cell biology.

We propose that secreted virulence factors are not released individually as naked proteins into the surrounding milieu where they may randomly contact the surface of the host cell, but instead bacterial derived OMV deliver multiple virulence factors simultaneously and directly into the host cell cytoplasm in a coordinated manner.

Flexible conductive polypyrrole nanocomposite membranes based on bacterial cellulose with amphiphobicity. Flexible conductive polypyrrole nanocomposite membranes based on bacterial cellulose BC with amphiphobicity have been successfully prepared through in situ chemical synthesis and then infiltrated with polysiloxane solution. The results suggested that polypyrrole PPy nanoparticles deposited on the surface of BC formed a continuous core-shell structure by taking along the BC template.

After modification with polysiloxane, the surface characteristics of the conductive BC membranes changed from highly hydrophilic to hydrophobic. The AFM images revealed that the roughness of samples after polysiloxane treatment increased along with the increase of pyrrole concentration. The contact angles CAs data revealed that the highest water contact angle and highest oil contact angle are The conductivity of the amphiphobic membranes with excellent flexibility reached 0.

It opened a new field of potential applications of BC materials. Published by Elsevier Ltd. Bacterial glyphosate resistance conferred by overexpression of an E. Herbicide resistance in commercial glyphosate-resistant crops is due to expression of a variant form of a bacterial 5-enolpyruvylshikimatephosphate synthase with a significantly decreased binding affinity for glyphosate at the target site of the enzyme. All kinetoplastid parasites, including protozoa such as Leishmania species, Trypanosoma brucei, and Trypanosoma cruzi that cause devastating diseases in humans and animals, are flagellated throughout their life cycles.

Although flagella were originally thought of primarily as motility organelles, flagellar functions in other critical processes, especially in sensing and signal transduction, have become more fully appreciated in the recent past.

The flagellar membrane is a highly specialized subdomain of the surface membrane, and flagellar membrane proteins are likely to be critical components for all the biologically important roles of flagella.

In this review, we summarize recent discoveries relevant to flagellar membrane proteins in these parasites, including the identification of such proteins, investigation of their biological functions, and mechanisms of selective trafficking to the flagellar membrane. Prospects for future investigations and current unsolved problems are highlighted.

Swimming performance of Bradyrhizobium diazoefficiens is an emergent property of its two flagellar systems. Many bacterial species use flagella for self-propulsion in aqueous media. In the soil, which is a complex and structured environment, water is found in microscopic channels where viscosity and water potential depend on the composition of the soil solution and the degree of soil water saturation.

Therefore, the motility of soil bacteria might have special requirements. An important soil bacterial genus is Bradyrhizobium, with species that possess one flagellar system and others with two different flagellar systems. Among the latter is B. These two flagellar systems were observed here as functionally integrated in a swimming performance that emerged as an epistatic interaction between those appendages.

In addition, each flagellum seemed engaged in a particular task that might be required for swimming oriented toward chemoattractants near the soil inner surfaces at viscosities that may occur after the loss of soil gravitational water. Because the possession of two flagellar systems is not general in Bradyrhizobium or in related genera that coexist in the same environment, there may be an adaptive tradeoff between energetic costs and ecological benefits among these different species.

A protein thermometer controls temperature-dependent transcription of flagellar motility genes in Listeria monocytogenes. Full Text Available Facultative bacterial pathogens must adapt to multiple stimuli to persist in the environment or establish infection within a host.

Temperature is often utilized as a signal to control expression of virulence genes necessary for infection or genes required for persistence in the environment. However, very little is known about the molecular mechanisms that allow bacteria to adapt and respond to temperature fluctuations. Listeria monocytogenes Lm is a food-borne, facultative intracellular pathogen that uses flagellar motility to survive in the extracellular environment and to enhance initial invasion of host cells during infection.

In this study, we determined that GmaR is also a protein thermometer that controls temperature-dependent transcription of flagellar motility genes. Two-hybrid and gel mobility shift analyses indicated that the interaction between MogR and GmaR is temperature sensitive. Using circular dichroism and limited proteolysis, we determined that GmaR undergoes a temperature-dependent conformational change as temperature is elevated.

GmaR complex is less stable. Since MogR represses transcription of all flagellar motility genes, including transcription of gmaR, changes in the stability of the MogR: GmaR anti-repression complex, due to conformational changes in GmaR, mediates repression or de-repression of flagellar motility genes in Lm.

Thus, GmaR functions as. Load Response of the Flagellar Beat. Cilia and flagella exhibit regular bending waves that perform mechanical work on the surrounding fluid, to propel cellular swimmers and pump fluids inside organisms. Here, we quantify a force-velocity relationship of the beating flagellum, by exposing flagellated Chlamydomonas cells to controlled microfluidic flows.

A simple theory of flagellar limit-cycle oscillations, calibrated by measurements in the absence of flow, reproduces this relationship quantitatively. We derive a link between the energy efficiency of the flagellar beat and its ability to synchronize to oscillatory flows.

Identification of Archaea-specific chemotaxis proteins which interact with the flagellar apparatus. Full Text Available Abstract Background Archaea share with bacteria the ability to bias their movement towards more favorable locations, a process known as taxis. Two molecular systems drive this process: The first consists of the flagellum, the flagellar motor, and its switch, which allows cells to reverse the rotation of flagella. The second targets the flagellar motor switch in order to modulate the switching frequency in response to external stimuli.

While the signal transduction system is conserved throughout archaea and bacteria, the archaeal flagellar apparatus is different from the bacterial one. The proteins constituting the flagellar motor and its switch in archaea have not yet been identified, and the connection between the bacterial -like chemotaxis signal transduction system and the archaeal motility apparatus is unknown. In-frame deletion strains for all three proteins were generated and analyzed as follows: In these mutants, flagella rotate only clockwise, resulting in exclusively forward swimming cells that are unable to respond to tactic signals.

Deletion of the second DUF protein had only minimal effects. Seroprevalence in chickens against campylobacter jejuni flagellar capping protein FliD in selected areas of the U. Campylobacter jejuni, a Gram-negative rod, is a zoonotic pathogen associated with human acute bacterial gastroenteritis. Poultry products are regarded as a major source for human infection with this microorganism.

We have demonstrated that the flagellar capping protein FliD of C. The stator consists of several units located in the cytoplasmic membrane surrounding the flagellar drive shaft. Studies on flagellar motors of several bacterial species have provided evidence that the number as well as the retention time of stators coupled to the motor is highly dynamic and depends on the environmental conditions.

Notably, numerous species possess more than a single distinct set of stators. It is likely that the presence of different stator units enables these bacteria to adjust the flagellar motor properties and function to meet the environmental requirements. Here, we describe a method to determine stator dynamics by fluorescence microscopy, demonstrating how bacteria can change the composition of an intricate molecular machine according to environmental conditions.

Full Text Available Molecular motors, which are precision-engineered by nature, offer exciting possibilities for bio-hybrid engineered systems. This review describes the fundamental biological insights and fascinating potentials of these remarkable sensing and actuation machines, in particular bacterial flagellar motors, as well as their engineering perspectives with regard to applications in bio-engineered hybrid systems and nanobiotechnology.

Microhydrodynamics and complex fluids. It will be useful to technicians, medical scientists and pharmaceutical chemists as a source of detailed information on advanced flow processes. The articles are of a high scientific standard and include interesting examples from many different areas of rheology. The flagellar -specific transcription factor, sigma28, is the Type III secretion chaperone for the flagellar -specific anti-sigma28 factor FlgM.

The sigma 28 protein is a member of the bacterial sigma 70 -family of transcription factors that directs RNA polymerase to flagellar late class 3 promoters. The sigma 28 protein is regulated in response to flagellar assembly by the anti-sigma 28 factor FlgM.

FlgM inhibits sigma 28 -dependent transcription of genes whose products are needed late in assembly until the flagellar basal motor structure, the hook-basal body HBB , is constructed. A second function for the sigma 28 transcription factor has been discovered: Transcription-specific mutants in sigma 28 were isolated that remained competent for FlgM-facilitated secretion separating the transcription and secretion-facilitation activities of sigma Conversely, we also describe the isolation of mutants in sigma 28 that are specific for FlgM-facilitated secretion.

Thus, a novel role for a sigma 70 -family transcription factor is described. Flagellar Motility of Trypanosoma cruzi Epimastigotes. Full Text Available The hemoflagellate Trypanosoma cruzi is the causative agent of American trypanosomiasis.

Despite the importance of motility in the parasite life cycle, little is known about T. Using video microscopy and quantitative vectorial analysis of epimastigote trajectories, we find a forward parasite motility defined by tip-to-base symmetrical flagellar beats. This motion is occasionally interrupted by base-to-tip highly asymmetric beats, which represent the ciliary beat of trypanosomatid flagella. The switch between flagellar and ciliary beating facilitates the parasite's reorientation, which produces a large variability of movement and trajectories that results in different distance ranges traveled by the cells.

An analysis of the distance, speed, and rotational angle indicates that epimastigote movement is not completely random, and the phenomenon is highly dependent on the parasite behavior and is characterized by directed and tumbling parasite motion as well as their combination, resulting in the alternation of rectilinear and intricate motility paths. Full Text Available Most bacteria that swim are propelled by flagellar filaments, which are driven by a rotary motor powered by proton flux.

The mechanism of the flagellar motor is discussed by reforming the model proposed by the present authors in It is shown that the mean strength of Coulomb field produced by a proton passing the channel is very strong in the Mot assembly so that the Mot assembly can be a shear force generator and induce the flagellar rotation.

The model gives clear calculation results in agreement with experimental observations, e g. An unusual promoter controls cell-cycle regulation and dependence on DNA replication of the Caulobacter fliLM early flagellar operon. Transcription of flagellar genes in Caulobacter crecentus is programmed to occur during the predivisional stage of the cell cycle.

The mechanism of activation of Class II flagellar genes, the highest identified genes in the Caulobacter flagellar hierarchy, is unknown. As a step toward understanding this process, we have defined cis-acting sequences necessary for expression of a Class II flagellar operon, fliLM. Deletion analysis indicated that a 55 bp DNA fragment was sufficient for normal, temporally regulated promoter activity.

Transcription from this promoter-containing fragment was severely reduced when chromosomal DNA replication was inhibited. Extensive mutational analysis of the promoter region from to -5 identified functionally important nucleotides at and , between and , and at , which correlates well with sequences conserved between fliLM and the analogous regions of two other Class II flagellar operons.

The promoter sequence does not resemble that recognized by any known bacterial sigma factor. Models for regulation of Caulobacter early flagellar promoters are discussed in which RNA polymerase containing a novel sigma subunit interacts with an activation factor bound to the central region of the promoter. A role for the membrane in regulating Chlamydomonas flagellar length.

Full Text Available Flagellar assembly requires coordination between the assembly of axonemal proteins and the assembly of the flagellar membrane and membrane proteins. Fully grown steady-state Chlamydomonas flagella release flagellar vesicles from their tips and failure to resupply membrane should affect flagellar length. To study vesicle release, plasma and flagellar membrane surface proteins were vectorially pulse-labeled and flagella and vesicles were analyzed for biotinylated proteins.

Brefeldin-A destroyed Chlamydomonas Golgi, inhibited the secretory pathway, inhibited flagellar regeneration, and induced full-length flagella to disassemble within 6 hrs, consistent with flagellar disassembly being induced by a failure to resupply membrane. In contrast to membrane lipids, a pool of biotinylatable membrane proteins was identified that was sufficient to resupply flagella as they released vesicles for 6 hrs in the absence of protein synthesis and to support one and nearly two regenerations of flagella following amputation.

These studies reveal the importance of the secretory pathway to assemble and maintain full-length flagella. Flagellar biosynthesis exerts temporal regulation of secretion of specific Campylobacter jejuni colonization and virulence determinants. The Campylobacter jejuni flagellum exports both proteins that form the flagellar organelle for swimming motility and colonization and virulence factors that promote commensal colonization of the avian intestinal tract or invasion of human intestinal cells respectively.

We explored how the C. Flagellar biogenesis was observed to exert temporal control of secretion of these proteins, indicating that a bolus of secretion of colonization and virulence factors occurs during hook biogenesis with filament polymerization itself reducing secretion of these factors.

Furthermore, we found that intramolecular and intermolecular requirements for flagellar -dependent secretion of these proteins were most reminiscent to those for flagellin secretion. Importantly, we discovered that secretion of one colonization and virulence factor, CiaI, was not required for invasion of human colonic cells, which counters previous hypotheses for how this protein functions during invasion. Instead, secretion of CiaI was essential for C. Our work provides insight into the versatility of the bacterial flagellum as a secretory machine that can export proteins promoting diverse biological processes.

The Bacillus subtilis flagellar regulatory protein sigma D: Flagellar biosynthesis requires an alternative sigma sigma subunit of RNA polymerase to allow recognition of the promoters for flagellin and other late genes of the flagellar regulon. We have now overproduced and characterized Bacillus subtilis sigma D: Limited protease digestion studies indicate that sigma D contains an amino-terminal domain, comprising conserved regions 1.

The protease-sensitive region between these two domains correlates with a region of very low sequence conservation among bacterial sigma factors. Unlike the primary sigma factor, sigma D binds to DNA. In non-denaturing polyacrylamide gel electrophoresis the sigma D-DNA complex has an apparent equilibrium dissociation constant of 1 microM. Binding of sigma D to the promoter for flagellin, PD-6, appears to lead to an altered DNA structure near the and recognition elements as detected by DNase I footprinting and by the enhanced reactivity of several bases to dimethylsulfate.

Flagellar synchronization through direct hydrodynamic interactions. Flows generated by ensembles of flagella are crucial to development, motility and sensing, but the mechanisms behind this striking coordination remain unclear.

We present novel experiments in which two micropipette-held somatic cells of Volvox carteri, with distinct intrinsic beating frequencies, are studied by high-speed imaging as a function of their separation and orientation. Analysis of time series shows that the interflagellar coupling, constrained by lack of connections between cells to be hydrodynamical, exhibits a spatial dependence consistent with theory.

At close spacings it produces robust synchrony for thousands of beats, while at increasing separations synchrony is degraded by stochastic processes. Manipulation of the relative flagellar orientation reveals in-phase and antiphase states, consistent with dynamical theories.

Flagellar tracking with exquisite precision reveals waveform changes that result from hydrodynamic coupling. This study proves unequivocally that flagella coupled solely through a fluid can achieve robust synchrony despite differences in their intrinsic properties.

For construction of the bacterial flagellum, flagellar proteins are exported via its specific export apparatus from the cytoplasm to the distal end of the growing flagellar structure. FlhA is a TM export gate protein and plays important roles in energy coupling of protein translocation. However, the energy coupling mechanism remains unknown. Here, we performed a cross-complementation assay to measure robustness of the energy transduction system of the export apparatus against genetic perturbations.

We propose that FliH and FliI ensure robust and efficient energy coupling of protein export during flagellar assembly. Nonlinear amplitude dynamics in flagellar beating. The physical basis of flagellar and ciliary beating is a major problem in biology which is still far from completely understood. The fundamental cytoskeleton structure of cilia and flagella is the axoneme, a cylindrical array of microtubule doublets connected by passive crosslinkers and dynein motor proteins. The complex interplay of these elements leads to the generation of self-organized bending waves.

Although many mathematical models have been proposed to understand this process, few attempts have been made to assess the role of dyneins on the nonlinear nature of the axoneme. Here, we investigate the nonlinear dynamics of flagella by considering an axonemal sliding control mechanism for dynein activity. This approach unveils the nonlinear selection of the oscillation amplitudes, which are typically either missed or prescribed in mathematical models.

The explicit set of nonlinear equations are derived and solved numerically. Our analysis reveals the spatiotemporal dynamics of dynein populations and flagell With few exceptions, the function of cilia and flagella is to beat rhythmically and set up relative motion between themselves and the liquid that surrounds them.

The molecular basis of axonemal movement is understood in considerable detail, with the exception of the mechanism that provides its rhythmical or oscillatory quality. Some kind of repetitive 'switching' event is assumed to occur; there are several proposals regarding the nature of the 'switch' and how it might operate. Herein I first summarise all the factors known to influence the rate of the oscillation the beating frequency.

Many of these factors exert their effect through modulating the mean sliding velocity between the nine doublet microtubules of the axoneme, this velocity being the determinant of bend growth rate and bend propagation rate. Then I explain six proposed mechanisms for flagellar oscillation and review the evidence on which they are based. Finally, I attempt to derive an economical synthesis, drawing for preference on experimental research that has been minimally disruptive of the intricate structure of the axoneme.

The 'provisional synthesis' is that flagellar oscillation emerges from an effect of passive sliding direction on the dynein arms. Sliding in one direction facilitates force-generating cycles and dynein-to-dynein synchronisation along a doublet; sliding in the other direction is inhibitory. The direction of the initial passive sliding normally oscillates because it is controlled hydrodynamically through the alternating direction of the propulsive thrust.

However, in the absence of such regulation, there can be a perpetual, mechanical self-triggering through a reversal of sliding direction due to the recoil of elastic structures that deform as a response to the prior active sliding.

This provisional synthesis may be a useful basis for further examination of the problem. Full Text Available Flagella are surface structures critical for motility and virulence of many bacterial species.

In Listeria monocytogenes, MogR tightly represses expression of flagellin FlaA during extracellular growth at 37 degrees C and during intracellular infection. MogR is also required for full virulence in a murine model of infection. Using in vitro and in vivo infection models, we determined that the severe virulence defect of MogR-negative bacteria is due to overexpression of FlaA. Specifically, overproduction of FlaA in MogR-negative bacteria caused pleiotropic defects in bacterial division chaining phenotype, intracellular spread, and virulence in mice.

Analysis of MogR protein levels demonstrated that modulation of MogR repression activity confers the temperature-specificity to flagellar motility gene expression. Epistasis analysis revealed that MogR repression of transcription is antagonized in a temperature-dependent manner by the DegU response regulator and that DegU further regulates FlaA levels through a posttranscriptional mechanism. These studies provide the first known example to our knowledge of a transcriptional repressor functioning as a master regulator controlling nonhierarchal expression of flagellar motility genes.

Scientific experiments are indispensable parts of Biochemistry and Molecular Biology. In this study, a comprehensive Biochemistry and Molecular Biology experiment about "Salmonella enterica" serovar Typhi Flagellar phase variation has been designed. It consisted of three parts, namely, inducement of bacterial Flagellar phase variation,…. The flagellar adenylate kinases of Trypanosoma cruzi.

Adenylate kinases ADK are key enzymes involved in cell energy management. Trypanosomatids present the highest number of variants in a single cell in comparison with the rest of the living organisms.

Interestingly, TcADK1 presents a stage-specific expression. This variant was detected in epimastigotes cells, and was completely absent in trypomastigotes and amastigotes, while TcADK4 is present in the major life cycle stages of T. Both variants are also regulated, in opposite ways, along the parasite growth curve suggesting that their expression depends on the intra- and extracellular conditions.

The presence of ADK variants in the flagellum would be critical for the provision of energy in a process of high ATP consumption such as cell motility. In situ ellipsometric study of surface immobilization of flagellar filaments. Protein filaments composed of thousands of subunits are promising candidates as sensing elements in biosensors.

In this work in situ spectroscopic ellipsometry is applied to monitor the surface immobilization of flagellar filaments. This study is the first step towards the development of layers of filamentous receptors for sensor applications. Surface activation is performed using silanization and a subsequent glutaraldehyde crosslinking. Structure of the flagellar filament layers immobilized on activated and non-activated Si wafer substrates is determined using a two-layer effective medium model that accounted for the vertical density distribution of flagellar filaments with lengths of nm bound to the surface.

The formation of the first interface layer can be explained by the multipoint covalent attachment of the filaments, while the second layer is mainly composed of tail pinned filaments floating upwards with the free parts.

As confirmed by atomic force microscopy, covalent immobilization resulted in an increased surface density compared to absorption. We show that DNA-based self-assembly can serve as a general and flexible tool to construct artificial flagella of several micrometers in length and only tens of nanometers in diameter. By attaching the DNA flagella to biocompatible magnetic microparticles, we provide a proof of concept demonstration of hybrid structures that, when rotated in an external magnetic field, propel by means of a flagellar bundle, similar to self-propelling peritrichous bacteria.

Our theoretical analysis predicts that flagellar bundles that possess a length-dependent bending stiffness should exhibit a superior swimming speed compared to swimmers with a single appendage. The DNA self-assembly method permits the realization of these improved flagellar bundles in good agreement with our quantitative model.

DNA flagella with well-controlled shape could fundamentally increase the functionality of fully biocompatible nanorobots and extend the scope and complexity of active materials. The load-response of the flagellar beat. We derive a link between the chemo-mechanical efficiency of the flagellar beat and its ability to synchronize to oscillatory flows. The CckA-ChpT-CtrA phosphorelay system is regulated by quorum sensing and controls flagellar motility in the marine sponge symbiont Ruegeria sp.

Full Text Available Bacteria respond to their environment via signal transduction pathways, often two-component type systems that function through phosphotransfer to control expression of specific genes. Phosphorelays are derived from two-component systems but are comprised of additional components.

The essential cckA-chpT-ctrA phosphorelay in Caulobacter crescentus has been well studied and is important in orchestrating the cell cycle, polar development and flagellar biogenesis. Although cckA, chpT and ctrA homologues are widespread among the Alphaproteobacteria, relatively few is known about their function in the large and ecologically significant Roseobacter clade of the Rhodobacterales.

In this study the cckA-chpT-ctrA system of the marine sponge symbiont Ruegeria sp. Our results reveal that the cckA, chpT and ctrA genes positively control flagellar biosynthesis. In contrast to C. KLH11 are non-essential and do not affect bacterial growth.

Gene fusion and transcript analyses provide evidence for ctrA autoregulation and the control of motility-related genes. Full Text Available Bactofilins are a widely conserved protein family implicated in cell shape maintenance and in bacterial motility.

The proteins are required for the establishment of flagellar hook- and filament structures, but apparently not for the formation of basal bodies. BacF assemblies are relatively static, and partially colocalize with flagellar basal bodies, while BacE assemblies are fewer per cell than those of BacF and are highly mobile. Tracking of BacE foci showed that the assemblies arrest at a single point for a few hundred milliseconds, showing that a putative interaction with flagellar structures would be transient and fast.

When overexpressed or expressed in a heterologous cell system, bactofilins can form filamentous structures, and also form multimers as purified proteins. Our data reveal a propensity for bactofilins to form filaments, however, in B. Bactofilins are a widely conserved protein family implicated in cell shape maintenance and in bacterial motility. Full Text Available The flagellar pocket constitutes an active and strategic site in the body of trypanosomatids i. Most importantly, the flagellar pocket is the unique site of surface protein export and nutrient uptake in trypanosomatids, and thus constitutes a key portal for the interaction with the host.

In this work, we identified and characterized a novel Trypanosoma cruzi protein, termed TCLP 1, that accumulates at the flagellar pocket area of parasite replicative forms, as revealed by biochemical, immuno-cytochemistry and electron microscopy techniques.

Different in silico analyses revealed that TCLP 1 is the founding member of a family of chimeric molecules restricted to trypanosomatids bearing, in addition to eukaryotic ubiquitin-like and protein-protein interacting domains, a motif displaying significant structural homology to bacterial multi-cargo chaperones involved in the secretion of virulence factors.

Using the fidelity of an homologous expression system we confirmed TCLP 1 sub-cellular distribution and showed that TCLP 1-over-expressing parasites display impaired survival and accelerated progression to late stationary phase under starvation conditions.

The reduced endocytic capacity of TCLP 1-over-expressors likely underlies at least in part this growth phenotype. TCLP 1 is involved in the uptake of extracellular macromolecules required for nutrition and hence in T. Due to the bacterial origin, sub-cellular distribution and putative function s, we propose TCLP 1 and related orthologs in trypanosomatids as appealing therapeutic targets for intervention against these health-threatening parasites.

The flagellar pocket constitutes an active and strategic site in the body of trypanosomatids i. Due to the bacterial origin, sub-cellular distribution and putative function s , we propose TCLP 1 and related orthologs in trypanosomatids as appealing therapeutic targets for intervention against these health-threatening parasites.

Type III secretion systems T3SSs are multiprotein molecular devices used by many Gram-negative bacterial pathogens to translocate effector proteins into eukaryotic cells.

A T3SS is also used for protein export in flagellar assembly, which promotes bacterial motility. The two systems are evolutionarily related, possessing highly conserved components in their export apparatuses. Its highly regulated movement is essential for the normal function of many organs; ciliopathies cause congenital defects, chronic respiratory tract infections and infertility.

We present an efficient method to obtain a quantitative description of flagellar motion, with high spatial and temporal resolution, from high speed video recording of bright field images. This highly automated tec Direct evidence of flagellar synchronization through hydrodynamic interactions.

Eukaryotic cilia and flagella exhibit striking coordination, from the synchronous beating of two flagella in Chlamydomonas to the metachronal waves and large-scale flows displayed by carpets of cilia. However, the precise mechanisms responsible for flagellar synchronization remain unclear.

We perform a series of experiments involving two individual flagella in a quiescent fluid. Cells are isolated from the colonial alga Volvox carteri, held in place at a fixed distance d, and oriented so that their flagellar beating planes coincide.

In this fashion, we are able to explicitly assess the role of hydrodynamics in achieving synchronization. For closely separated cells, the flagella are capable of exhibiting a phase-locked state for thousands of beats at a time, despite significant differences in their intrinsic frequencies. The coupling strength extracted through analysis of the synchronization statistics exhibits excellent agreement with hydrodynamic predictions.

This study unambiguously reveals that flagella coupled only through hydrodynamics are capable of exhibiting robust synchrony. Probing flagellar promoter occupancy in wild-type and mutant Caulobacter crescentus by chromatin immunoprecipitation. In the asymmetric predivisional cell of Caulobacter crescentus, TipF and TipN mark the cellular pole for future flagellar development.

TipN is localized to the flagellar pole before TipF and is essential for the proper placement of the flagellum in C.

We deduce that TipF contributes to proper expression of flagellar genes in C. Second-chance signal transduction explains cooperative flagellar switching. Full Text Available The reversal of flagellar motion switching results from the interaction between a switch complex of the flagellar rotor and a torque-generating stationary unit, or stator motor unit.

To explain the steeply cooperative ligand-induced switching, present models propose allosteric interactions between subunits of the rotor, but do not address the possibility of a reaction that stimulates a bidirectional motor unit to reverse direction of torque.

During flagellar motion, the binding of a ligand-bound switch complex at the dwell site could excite a motor unit. The probability that another switch complex of the rotor, moving according to steady-state rotation, will reach the same dwell site before that motor unit returns to ground state will be determined by the independent decay rate of the excited-state motor unit.

Here, we derive an analytical expression for the energy coupling between a switch complex and a motor unit of the stator complex of a flagellum, and demonstrate that this model accounts for the cooperative switching response without the need for allosteric interactions. The analytical result can be reproduced by simulation when 1 the motion of the rotor delivers a subsequent ligand-bound switch to the excited motor unit, thereby providing the excited motor unit with a second chance to remain excited, and 2 the outputs from multiple independent motor units are constrained to a single all-or-none event.

In this proposed model, a motor unit and switch complex represent the components of a mathematically defined signal transduction mechanism in which energy coupling is driven by steady-state and is regulated by stochastic ligand binding. Mathematical derivation of the model shows the analytical function to be a general form of the Hill equation Hill AV The possible effects of the aggregation of the molecules of haemoglobin on its dissociation curves.

Bioconvection is a form of collective motion that occurs spontaneously in the suspension of swimming microorganisms. In a previous study, we quantitatively described the "pattern transition," a phase transition phenomenon that so far has exclusively been observed in bioconvection of the unicellular green alga Chlamydomonas. We suggested that the transition could be induced by changes in the balance between the gravitational and shear-induced torques, both of which act to determine the orientation of the organism in the shear flow.

As both of the torques should be affected by the geometry of the Chlamydomonas cell, alteration in the flagellar waveform might change the extent of torque generation by altering overall geometry of the cell.

Based on this working hypothesis, we examined bioconvection behavior of two flagellar mutants of Chlamydomonas reinhardtii, ida1 and oda2, making reference to the wild type. Flagella of ida1 beat with an abnormal waveform, while flagella of oda2 show a normal waveform but lower beat frequency.

Two-axis view revealed the periodic movement of the settling blobs of ida1, while oda2 showed qualitatively similar behavior to that of wild type. Unexpectedly, ida1 showed stronger negative gravitaxis than did wild type, while oda2 showed relatively weak gravitaxis. These findings suggest that flagellar waveform, not swimming speed or beat frequency, strongly affect bioconvection behavior in C. Optimization of flagellar swimming by a model sperm.

The swimming of a bead-spring chain in a viscous incompressible fluid as a model of a sperm is studied in the framework of low Reynolds number hydrodynamics. The optimal mode in the class of planar flagellar strokes of small amplitude is determined on the basis of a generalized eigenvalue problem involving two matrices which can be evaluated from the mobility matrix of the set of spheres constituting the chain.

For an elastic chain with a cargo constraint for its spherical head, the actuating forces yielding a nearly optimal stroke can be determined. These can be used in a Stokesian dynamics simulation of large amplitude swimming. Biochemical characterization of tektins from sperm flagellar doublet microtubules. Tektins, protein components of stable protofilaments from sea urchin sperm flagellar outer doublet microtubules Linck, R. Only three types of electrically driven rotary motors exist in nature: This pattern was confirmed in swimming assays of stator-less Bacillus subtilis and Escherichia coli mutants expressing MotPS from B.

The finding will affect the understanding of the operating principles of flagellar motors and the molecular mechanisms of ion selectivity, the field of the evolution of environmental changes and stresses, and areas of nanotechnology. Modulation of Chlamydomonas reinhardtii flagellar motility by redox poise. Redox-based regulatory systems are essential for many cellular activities. Chlamydomonas reinhardtii exhibits alterations in motile behavior in response to different light conditions photokinesis.

We hypothesized that photokinesis is signaled by variations in cytoplasmic redox poise resulting from changes in chloroplast activity. Analysis of reactivated cell models revealed that this redox poise effect is mediated through the outer dynein arms ODAs.

These data indicate that redox poise directly affects ODAs and suggest that it may act in the control of flagellar motility. Marine bacterium Vibrio alginolyticus uses a single polar flagellum to navigate in an aqueous environment.

Similar to Escherichia coli cells, the polar flagellar motor has two states; when the motor is counter-clockwise, the cell swims forward and when the motor is clockwise, the cell swims backward. The short-time inhibition is sufficiently strong and long lasting, i. Structure of the microtubule-binding domain of flagellar dynein.

Flagellar dyneins are essential microtubule motors in eukaryotes, as they drive the beating motions of cilia and flagella. Unlike myosin and kinesin motors, the track binding mechanism of dyneins and the regulation between the strong and weak binding states remain obscure. The flap is positively charged and highly flexible. Despite the structural similarity to cytoplasmic MTBD, dynein-c MTBD shows only a small change in the microtubule- binding affinity depending on the registry change of coiled coil-sliding, whereby lacks the apparent strong binding state.

The surface charge distribution of dynein-c MTBD also differs from that of cytoplasmic MTBD, which suggests a difference in the microtubule-binding mechanism. Campylobacter jejuni is a causative pathogen of human acute bacterial gastroenteritis. Infected poultry products are regarded as a major source for human C.

The flagellar capping protein FliD is highly conserved among C. In this study, we used the FliD protein as a probe to survey the prevalence of C. A total of samples were tested. These results demonstrate that anti-FliD antibodies were prevalent in the poultry population in the areas of serum samples collected. This article is a U. Government work and is in the public domain in the USA.

Full Text Available The bacterial type III export apparatus is found in the flagellum and in the needle complex of some pathogenic Gram-negative bacteria. In the needle complex its function is to secrete effector proteins for infection into Eukaryotic cells. In the bacterial flagellum it exports specific proteins for the building of the flagellum during its assembly.

The export apparatus is composed of about five membrane proteins and three soluble proteins. The mechanism of the export apparatus is not fully understood. The five membrane proteins are well conserved and essential. Here a cross-complementation assay was performed: From cells expressing the chimeric AquSalFlhB protein, suppressor mutants with enhanced motility were isolated and the mutations were identified using whole genome sequencing.

Gain-of-function mutations were found in the gene encoding FlhA, another membrane protein of the type III export apparatus. The mutations were shown by reversed-phase high performance liquid chromatography to reduce the quinone pool of the cytoplasmic membrane. Ubiquinone biosynthesis could be restored for the strain bearing a mutated gene for 4-hydroxybenzoate octaprenyltransferase by the addition of excess exogenous 4-hydroxybenzoate.

Restoring the level of ubiquinone reduced flagella biogenesis with the AquSalFlhB chimera. The bacterial type III export apparatus is found in the flagellum and in the needle complex of some pathogenic Gram-negative bacteria. Restoring the level of ubiquinone reduced flagella biogenesis with the AquSalFlhB chimera demonstrating that the. The motility of microorganisms is influenced greatly by their hydrodynamic interactions with the fluidic environment they inhabit.

We show by direct experimental observation of the bi-flagellated alga Chlamydomonas reinhardtii that fluid elasticity and viscosity strongly influence the beating pattern - the gait - and thereby control the propulsion speed. The beating frequency and the wave speed characterizing the cyclical bending are both enhanced by fluid elasticity. Despite these enhancements, the net swimming speed of the alga is hindered for fluids that are sufficiently elastic.

The origin of this complex response lies in the interplay between the elasticity-induced changes in the spatial and temporal aspects of the flagellar cycle and the buildup and subsequent relaxation of elastic stresses during the power and recovery strokes.

Rab23 is a flagellar protein in Trypanosoma brucei. Full Text Available Abstract Background Rab small GTPases are important mediators of membrane transport, and orthologues frequently retain similar locations and functions, even between highly divergent taxa. In metazoan organisms Rab23 is an important negative regulator of Sonic hedgehog signaling and is crucial for correct development and differentiation of cellular lineages by virtue of an involvement in ciliary recycling.

Previously, we reported that Trypanosoma brucei Rab23 localized to the nuclear envelope 1, which is clearly inconsistent with the mammalian location and function. Here we sought to further investigate the role s of Rab23 in T. Despite evidence for considerable secondary loss, we found a clear correlation between a conventional flagellar structure and the presence of a Rab23 orthologue in the genome.

By epitope-tagging, Rab23 was localized and found to be present at the flagellum throughout the cell cycle. However, RNAi knockdown did not result in a flagellar defect, suggesting that Rab23 is not required for construction or maintenance of the flagellum. Conclusions The location of Rab23 at the flagellum is conserved between mammals and trypanosomes and the Rab23 gene is restricted to flagellated organisms. These data may suggest the presence of a Rabmediated signaling mechanism in trypanosomes.

TbFlabarin, a flagellar protein of Trypanosoma brucei, highlights differences between Leishmania and Trypanosoma flagellar -targeting signals. TbFlabarin is mainly expressed in the procyclic forms of the parasite and localized to the flagellum, but only when two palmitoylable cysteines at positions 3 and 4 are present.

TbFlabarin is more strongly attached to the membrane fraction than its Leishmania counterpart, as it resists complete solubilization with as much as 0. Expression ablation by RNA interference did not change parasite growth in culture, its morphology or apparent motility. Heterologous expression showed that neither TbFlabarin in L. Activation of the Campylobacter jejuni FlgSR two-component system is linked to the flagellar export apparatus.

Activation of sigma 54 -dependent gene expression essential for formation of flagella in Campylobacter jejuni requires the components of the inner membrane-localized flagellar export apparatus and the FlgSR two-component regulatory system.

In this study, we characterized the FlgS sensor kinase and how activation of the protein is linked to the flagellar export apparatus. We found that FlgS is localized to the C.

Mutants with incomplete flagellar export apparatuses produced wild-type levels of FlgS and FlgR, but they were defective for signaling through the FlgSR system. By using genetic approaches, we found that FlgSR activity is linked to and downstream of the flagellar export apparatus in a regulatory cascade that terminates in expression of sigma 54 -dependent flagellar genes. By analyzing defined flhB and fliI mutants of C. Considering that the flagellar export apparatuses of Escherichia coli and Salmonella species influence sigma 28 -dependent flagellar gene expression, our work expands the signaling activity of the apparatuses to include sigma 54 -dependent pathways of C.

This study indicates that these apparatuses have broader functions beyond flagellar protein secretion, including activation of essential two-component regulatory systems required for expression of sigma 54 -dependent flagellar genes. EscO, a functional and structural analog of the flagellar FliJ protein, is a positive regulator of EscN ATPase activity of the enteropathogenic Escherichia coli injectisome.

Consistent with its central role in protein secretion, it was found to interact with the ATPase EscN and its negative regulator, EscL, of the export apparatus. Overall, our data indicate that EscO is the virulence counterpart of the flagellar FliJ protein. The ultrastructure of Peridinium cinctum, was examined by serial sectioning with particular emphasis on the detailed construction of the flagellar apparatus. The pusular system of P. Zipping and Entanglement in Flagellar Bundle of E.

Role of Motile Cell Body. The course of a peritrichous bacterium such as E. However, the rotation of each flagellum generates counter body movements which in turn affect the flagellar dynamics. Using a detailed numerical model of an E. In particular, bundle formation occurs through a zipping motion in a remarkably rapid time, affected little by initial flagellar orientation.

A simplified analytical model supports our observations. Finally, we illustrate how entanglement, hydrodynamic interactions, and body movement contribute to zipping and bundling. Flagellar coordination in Chlamydomonas cells held on micropipettes. The two flagella of Chlamydomonas are known to beat synchronously: Analysis of a great number of shock responses revealed that in undulatory beats also periods of bilateral coordination are found and that the coordination type may change several times during a shock response, without concomitant changes of the beat envelope and the beat period.

In normal wt cells no coordination changes are found during breaststroke beating, but only short temporary asynchronies: During 2 or 3 normal beats of the cis flagellum, the trans flagellum performs 3 or 4 flat beats with a reduced beat envelope and a smaller beat period, resulting in one additional trans beat.

Long periods with flat beats of the same shape and beat period are found in both flagella of the non-phototactic mutant ptx1 and in defective wt E cells.

During these periods, the coordination is parallel, the two flagella beat alternately. A correlation between normal asynchronous trans beats and the parallel-coordinated beats in the presumably cis defective cells and also the undulatory beats is discussed. In the cis defective cells, a perpetual spontaneous change between parallel beats with small beat periods higher beat frequency and bilateral beats with greater beat periods lower beat frequency are observed and render questionable the existence of two different intrinsic beat frequencies of the two flagella cis and trans.

Asynchronies occur spontaneously but may also be induced by light changes, either step-up or step-down, but not by both stimuli in turn as breaststroke flagellar photoresponses BFPRs. Asynchronies are not involved in phototaxis. They are independent of the BFPRs, which are supposed to be the basis of phototaxis.

Both types of coordination must be assumed to be regulated. The kD tektin is substantially more hydrophobic, eluting between the two tubulins. The proline content correlates well with the fact that tektin filaments have twice as much alpha-helical content as tubulin.

Total hydrophobic amino acid content correlates with HPLC elution times for the tektins but not tubulins. The average amino acid composition of the tektins indicates that they resemble intermediate filament proteins, as originally postulated from structural, solubility, and electrophoretic properties. Tektins have higher cysteine and tryptophan contents than desmin and vimentin, which characteristically have only one residue of each, more closely resembling certain keratins in these amino acids.

Full Text Available Motility in the protozoan parasite Trypanosoma brucei is conferred by a single flagellum, attached alongside the cell, which moves the cell forward using a beat that is generated from tip-to-base.

TbIC was tagged In situ-and shown to fractionate with the inner arm components of the flagellum. RNAi knockdown of TbIC resulted in significantly reduced protein levels, mild growth defect and significant motility defects. These cells tended to cluster, exhibited slow and abnormal motility and some cells had partially or fully detached flagella.

Slight but significant increases were observed in the incidence of mis-localized or missing kinetoplasts. To document development of the TbIC knockdown phenotype over time, we performed a detailed analysis of flagellar detachment and motility changes over hours following induction of RNAi.

Detached flagella had abnormal beating, but abnormal beating was also observed in cells with no flagellar detachment, suggesting that TbIC has a direct, or primary, effect on the flagellar beat, whereas detachment is a secondary phenotype of TbIC knockdown. Our results are consistent with the role of TbIC as a regulator of motility, and has a phenotype amenable to more extensive structure-function analyses to further elucidate its role in the control of flagellar beat in T.

The nexin-dynein regulatory complex N-DRC , which is a major hub for the control of flagellar motility, contains at least 11 different subunits.

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Identification of Archaea-specific chemotaxis proteins which interact with the flagellar apparatus. Full Text Available Abstract Background Archaea share with bacteria the ability to bias their movement towards more favorable locations, a process known as taxis.

Two molecular systems drive this process: The first consists of the flagellum, the flagellar motor, and its switch, which allows cells to reverse the rotation of flagella. The second targets the flagellar motor switch in order to modulate the switching frequency in response to external stimuli. While the signal transduction system is conserved throughout archaea and bacteria, the archaeal flagellar apparatus is different from the bacterial one. The proteins constituting the flagellar motor and its switch in archaea have not yet been identified, and the connection between the bacterial -like chemotaxis signal transduction system and the archaeal motility apparatus is unknown.

In-frame deletion strains for all three proteins were generated and analyzed as follows: In these mutants, flagella rotate only clockwise, resulting in exclusively forward swimming cells that are unable to respond to tactic signals. Deletion of the second DUF protein had only minimal effects. Seroprevalence in chickens against campylobacter jejuni flagellar capping protein FliD in selected areas of the U.

Campylobacter jejuni, a Gram-negative rod, is a zoonotic pathogen associated with human acute bacterial gastroenteritis. Poultry products are regarded as a major source for human infection with this microorganism. We have demonstrated that the flagellar capping protein FliD of C. The stator consists of several units located in the cytoplasmic membrane surrounding the flagellar drive shaft. Studies on flagellar motors of several bacterial species have provided evidence that the number as well as the retention time of stators coupled to the motor is highly dynamic and depends on the environmental conditions.

Notably, numerous species possess more than a single distinct set of stators. It is likely that the presence of different stator units enables these bacteria to adjust the flagellar motor properties and function to meet the environmental requirements. Here, we describe a method to determine stator dynamics by fluorescence microscopy, demonstrating how bacteria can change the composition of an intricate molecular machine according to environmental conditions.

Full Text Available Molecular motors, which are precision-engineered by nature, offer exciting possibilities for bio-hybrid engineered systems. This review describes the fundamental biological insights and fascinating potentials of these remarkable sensing and actuation machines, in particular bacterial flagellar motors, as well as their engineering perspectives with regard to applications in bio-engineered hybrid systems and nanobiotechnology.

Microhydrodynamics and complex fluids. It will be useful to technicians, medical scientists and pharmaceutical chemists as a source of detailed information on advanced flow processes. The articles are of a high scientific standard and include interesting examples from many different areas of rheology. The flagellar -specific transcription factor, sigma28, is the Type III secretion chaperone for the flagellar -specific anti-sigma28 factor FlgM. The sigma 28 protein is a member of the bacterial sigma 70 -family of transcription factors that directs RNA polymerase to flagellar late class 3 promoters.

The sigma 28 protein is regulated in response to flagellar assembly by the anti-sigma 28 factor FlgM. FlgM inhibits sigma 28 -dependent transcription of genes whose products are needed late in assembly until the flagellar basal motor structure, the hook-basal body HBB , is constructed.

A second function for the sigma 28 transcription factor has been discovered: Transcription-specific mutants in sigma 28 were isolated that remained competent for FlgM-facilitated secretion separating the transcription and secretion-facilitation activities of sigma Conversely, we also describe the isolation of mutants in sigma 28 that are specific for FlgM-facilitated secretion.

Thus, a novel role for a sigma 70 -family transcription factor is described. Flagellar Motility of Trypanosoma cruzi Epimastigotes. Full Text Available The hemoflagellate Trypanosoma cruzi is the causative agent of American trypanosomiasis. Despite the importance of motility in the parasite life cycle, little is known about T.

Using video microscopy and quantitative vectorial analysis of epimastigote trajectories, we find a forward parasite motility defined by tip-to-base symmetrical flagellar beats.

This motion is occasionally interrupted by base-to-tip highly asymmetric beats, which represent the ciliary beat of trypanosomatid flagella. The switch between flagellar and ciliary beating facilitates the parasite's reorientation, which produces a large variability of movement and trajectories that results in different distance ranges traveled by the cells. An analysis of the distance, speed, and rotational angle indicates that epimastigote movement is not completely random, and the phenomenon is highly dependent on the parasite behavior and is characterized by directed and tumbling parasite motion as well as their combination, resulting in the alternation of rectilinear and intricate motility paths.

Full Text Available Most bacteria that swim are propelled by flagellar filaments, which are driven by a rotary motor powered by proton flux. The mechanism of the flagellar motor is discussed by reforming the model proposed by the present authors in It is shown that the mean strength of Coulomb field produced by a proton passing the channel is very strong in the Mot assembly so that the Mot assembly can be a shear force generator and induce the flagellar rotation.

The model gives clear calculation results in agreement with experimental observations, e g. An unusual promoter controls cell-cycle regulation and dependence on DNA replication of the Caulobacter fliLM early flagellar operon. Transcription of flagellar genes in Caulobacter crecentus is programmed to occur during the predivisional stage of the cell cycle. The mechanism of activation of Class II flagellar genes, the highest identified genes in the Caulobacter flagellar hierarchy, is unknown.

As a step toward understanding this process, we have defined cis-acting sequences necessary for expression of a Class II flagellar operon, fliLM. Deletion analysis indicated that a 55 bp DNA fragment was sufficient for normal, temporally regulated promoter activity. Transcription from this promoter-containing fragment was severely reduced when chromosomal DNA replication was inhibited. Extensive mutational analysis of the promoter region from to -5 identified functionally important nucleotides at and , between and , and at , which correlates well with sequences conserved between fliLM and the analogous regions of two other Class II flagellar operons.

The promoter sequence does not resemble that recognized by any known bacterial sigma factor. Models for regulation of Caulobacter early flagellar promoters are discussed in which RNA polymerase containing a novel sigma subunit interacts with an activation factor bound to the central region of the promoter. A role for the membrane in regulating Chlamydomonas flagellar length.

Full Text Available Flagellar assembly requires coordination between the assembly of axonemal proteins and the assembly of the flagellar membrane and membrane proteins. Fully grown steady-state Chlamydomonas flagella release flagellar vesicles from their tips and failure to resupply membrane should affect flagellar length. To study vesicle release, plasma and flagellar membrane surface proteins were vectorially pulse-labeled and flagella and vesicles were analyzed for biotinylated proteins.

Brefeldin-A destroyed Chlamydomonas Golgi, inhibited the secretory pathway, inhibited flagellar regeneration, and induced full-length flagella to disassemble within 6 hrs, consistent with flagellar disassembly being induced by a failure to resupply membrane.

In contrast to membrane lipids, a pool of biotinylatable membrane proteins was identified that was sufficient to resupply flagella as they released vesicles for 6 hrs in the absence of protein synthesis and to support one and nearly two regenerations of flagella following amputation. These studies reveal the importance of the secretory pathway to assemble and maintain full-length flagella. Flagellar biosynthesis exerts temporal regulation of secretion of specific Campylobacter jejuni colonization and virulence determinants.

The Campylobacter jejuni flagellum exports both proteins that form the flagellar organelle for swimming motility and colonization and virulence factors that promote commensal colonization of the avian intestinal tract or invasion of human intestinal cells respectively.

We explored how the C. Flagellar biogenesis was observed to exert temporal control of secretion of these proteins, indicating that a bolus of secretion of colonization and virulence factors occurs during hook biogenesis with filament polymerization itself reducing secretion of these factors.

Furthermore, we found that intramolecular and intermolecular requirements for flagellar -dependent secretion of these proteins were most reminiscent to those for flagellin secretion. Importantly, we discovered that secretion of one colonization and virulence factor, CiaI, was not required for invasion of human colonic cells, which counters previous hypotheses for how this protein functions during invasion.

Instead, secretion of CiaI was essential for C. Our work provides insight into the versatility of the bacterial flagellum as a secretory machine that can export proteins promoting diverse biological processes. The Bacillus subtilis flagellar regulatory protein sigma D: Flagellar biosynthesis requires an alternative sigma sigma subunit of RNA polymerase to allow recognition of the promoters for flagellin and other late genes of the flagellar regulon.

We have now overproduced and characterized Bacillus subtilis sigma D: Limited protease digestion studies indicate that sigma D contains an amino-terminal domain, comprising conserved regions 1. The protease-sensitive region between these two domains correlates with a region of very low sequence conservation among bacterial sigma factors.

Unlike the primary sigma factor, sigma D binds to DNA. In non-denaturing polyacrylamide gel electrophoresis the sigma D-DNA complex has an apparent equilibrium dissociation constant of 1 microM. Binding of sigma D to the promoter for flagellin, PD-6, appears to lead to an altered DNA structure near the and recognition elements as detected by DNase I footprinting and by the enhanced reactivity of several bases to dimethylsulfate.

Flagellar synchronization through direct hydrodynamic interactions. Flows generated by ensembles of flagella are crucial to development, motility and sensing, but the mechanisms behind this striking coordination remain unclear. We present novel experiments in which two micropipette-held somatic cells of Volvox carteri, with distinct intrinsic beating frequencies, are studied by high-speed imaging as a function of their separation and orientation.

Analysis of time series shows that the interflagellar coupling, constrained by lack of connections between cells to be hydrodynamical, exhibits a spatial dependence consistent with theory.

At close spacings it produces robust synchrony for thousands of beats, while at increasing separations synchrony is degraded by stochastic processes. Manipulation of the relative flagellar orientation reveals in-phase and antiphase states, consistent with dynamical theories.

Flagellar tracking with exquisite precision reveals waveform changes that result from hydrodynamic coupling. This study proves unequivocally that flagella coupled solely through a fluid can achieve robust synchrony despite differences in their intrinsic properties.

For construction of the bacterial flagellum, flagellar proteins are exported via its specific export apparatus from the cytoplasm to the distal end of the growing flagellar structure. FlhA is a TM export gate protein and plays important roles in energy coupling of protein translocation. However, the energy coupling mechanism remains unknown. Here, we performed a cross-complementation assay to measure robustness of the energy transduction system of the export apparatus against genetic perturbations.

We propose that FliH and FliI ensure robust and efficient energy coupling of protein export during flagellar assembly. Nonlinear amplitude dynamics in flagellar beating.

The physical basis of flagellar and ciliary beating is a major problem in biology which is still far from completely understood. The fundamental cytoskeleton structure of cilia and flagella is the axoneme, a cylindrical array of microtubule doublets connected by passive crosslinkers and dynein motor proteins. The complex interplay of these elements leads to the generation of self-organized bending waves. Although many mathematical models have been proposed to understand this process, few attempts have been made to assess the role of dyneins on the nonlinear nature of the axoneme.

Here, we investigate the nonlinear dynamics of flagella by considering an axonemal sliding control mechanism for dynein activity. This approach unveils the nonlinear selection of the oscillation amplitudes, which are typically either missed or prescribed in mathematical models. The explicit set of nonlinear equations are derived and solved numerically. Our analysis reveals the spatiotemporal dynamics of dynein populations and flagell With few exceptions, the function of cilia and flagella is to beat rhythmically and set up relative motion between themselves and the liquid that surrounds them.

The molecular basis of axonemal movement is understood in considerable detail, with the exception of the mechanism that provides its rhythmical or oscillatory quality. Some kind of repetitive 'switching' event is assumed to occur; there are several proposals regarding the nature of the 'switch' and how it might operate. Herein I first summarise all the factors known to influence the rate of the oscillation the beating frequency.

Many of these factors exert their effect through modulating the mean sliding velocity between the nine doublet microtubules of the axoneme, this velocity being the determinant of bend growth rate and bend propagation rate. Then I explain six proposed mechanisms for flagellar oscillation and review the evidence on which they are based. Finally, I attempt to derive an economical synthesis, drawing for preference on experimental research that has been minimally disruptive of the intricate structure of the axoneme.

The 'provisional synthesis' is that flagellar oscillation emerges from an effect of passive sliding direction on the dynein arms. Sliding in one direction facilitates force-generating cycles and dynein-to-dynein synchronisation along a doublet; sliding in the other direction is inhibitory. The direction of the initial passive sliding normally oscillates because it is controlled hydrodynamically through the alternating direction of the propulsive thrust.

However, in the absence of such regulation, there can be a perpetual, mechanical self-triggering through a reversal of sliding direction due to the recoil of elastic structures that deform as a response to the prior active sliding.

This provisional synthesis may be a useful basis for further examination of the problem. Full Text Available Flagella are surface structures critical for motility and virulence of many bacterial species.

In Listeria monocytogenes, MogR tightly represses expression of flagellin FlaA during extracellular growth at 37 degrees C and during intracellular infection. MogR is also required for full virulence in a murine model of infection. Using in vitro and in vivo infection models, we determined that the severe virulence defect of MogR-negative bacteria is due to overexpression of FlaA.

Specifically, overproduction of FlaA in MogR-negative bacteria caused pleiotropic defects in bacterial division chaining phenotype, intracellular spread, and virulence in mice. Analysis of MogR protein levels demonstrated that modulation of MogR repression activity confers the temperature-specificity to flagellar motility gene expression. Epistasis analysis revealed that MogR repression of transcription is antagonized in a temperature-dependent manner by the DegU response regulator and that DegU further regulates FlaA levels through a posttranscriptional mechanism.

These studies provide the first known example to our knowledge of a transcriptional repressor functioning as a master regulator controlling nonhierarchal expression of flagellar motility genes. Scientific experiments are indispensable parts of Biochemistry and Molecular Biology. In this study, a comprehensive Biochemistry and Molecular Biology experiment about "Salmonella enterica" serovar Typhi Flagellar phase variation has been designed.

It consisted of three parts, namely, inducement of bacterial Flagellar phase variation,…. The flagellar adenylate kinases of Trypanosoma cruzi. Adenylate kinases ADK are key enzymes involved in cell energy management. Trypanosomatids present the highest number of variants in a single cell in comparison with the rest of the living organisms.

Interestingly, TcADK1 presents a stage-specific expression. This variant was detected in epimastigotes cells, and was completely absent in trypomastigotes and amastigotes, while TcADK4 is present in the major life cycle stages of T.

Both variants are also regulated, in opposite ways, along the parasite growth curve suggesting that their expression depends on the intra- and extracellular conditions. The presence of ADK variants in the flagellum would be critical for the provision of energy in a process of high ATP consumption such as cell motility.

In situ ellipsometric study of surface immobilization of flagellar filaments. Protein filaments composed of thousands of subunits are promising candidates as sensing elements in biosensors.

In this work in situ spectroscopic ellipsometry is applied to monitor the surface immobilization of flagellar filaments. This study is the first step towards the development of layers of filamentous receptors for sensor applications.

Surface activation is performed using silanization and a subsequent glutaraldehyde crosslinking. Structure of the flagellar filament layers immobilized on activated and non-activated Si wafer substrates is determined using a two-layer effective medium model that accounted for the vertical density distribution of flagellar filaments with lengths of nm bound to the surface. The formation of the first interface layer can be explained by the multipoint covalent attachment of the filaments, while the second layer is mainly composed of tail pinned filaments floating upwards with the free parts.

As confirmed by atomic force microscopy, covalent immobilization resulted in an increased surface density compared to absorption. We show that DNA-based self-assembly can serve as a general and flexible tool to construct artificial flagella of several micrometers in length and only tens of nanometers in diameter. By attaching the DNA flagella to biocompatible magnetic microparticles, we provide a proof of concept demonstration of hybrid structures that, when rotated in an external magnetic field, propel by means of a flagellar bundle, similar to self-propelling peritrichous bacteria.

Our theoretical analysis predicts that flagellar bundles that possess a length-dependent bending stiffness should exhibit a superior swimming speed compared to swimmers with a single appendage. The DNA self-assembly method permits the realization of these improved flagellar bundles in good agreement with our quantitative model. DNA flagella with well-controlled shape could fundamentally increase the functionality of fully biocompatible nanorobots and extend the scope and complexity of active materials.

The load-response of the flagellar beat. We derive a link between the chemo-mechanical efficiency of the flagellar beat and its ability to synchronize to oscillatory flows. The CckA-ChpT-CtrA phosphorelay system is regulated by quorum sensing and controls flagellar motility in the marine sponge symbiont Ruegeria sp. Full Text Available Bacteria respond to their environment via signal transduction pathways, often two-component type systems that function through phosphotransfer to control expression of specific genes.

Phosphorelays are derived from two-component systems but are comprised of additional components. The essential cckA-chpT-ctrA phosphorelay in Caulobacter crescentus has been well studied and is important in orchestrating the cell cycle, polar development and flagellar biogenesis.

Although cckA, chpT and ctrA homologues are widespread among the Alphaproteobacteria, relatively few is known about their function in the large and ecologically significant Roseobacter clade of the Rhodobacterales.

In this study the cckA-chpT-ctrA system of the marine sponge symbiont Ruegeria sp. Our results reveal that the cckA, chpT and ctrA genes positively control flagellar biosynthesis.

In contrast to C. KLH11 are non-essential and do not affect bacterial growth. Gene fusion and transcript analyses provide evidence for ctrA autoregulation and the control of motility-related genes. Full Text Available Bactofilins are a widely conserved protein family implicated in cell shape maintenance and in bacterial motility. The proteins are required for the establishment of flagellar hook- and filament structures, but apparently not for the formation of basal bodies.

BacF assemblies are relatively static, and partially colocalize with flagellar basal bodies, while BacE assemblies are fewer per cell than those of BacF and are highly mobile. Tracking of BacE foci showed that the assemblies arrest at a single point for a few hundred milliseconds, showing that a putative interaction with flagellar structures would be transient and fast.

When overexpressed or expressed in a heterologous cell system, bactofilins can form filamentous structures, and also form multimers as purified proteins. Our data reveal a propensity for bactofilins to form filaments, however, in B.

Bactofilins are a widely conserved protein family implicated in cell shape maintenance and in bacterial motility. Full Text Available The flagellar pocket constitutes an active and strategic site in the body of trypanosomatids i.

Most importantly, the flagellar pocket is the unique site of surface protein export and nutrient uptake in trypanosomatids, and thus constitutes a key portal for the interaction with the host. In this work, we identified and characterized a novel Trypanosoma cruzi protein, termed TCLP 1, that accumulates at the flagellar pocket area of parasite replicative forms, as revealed by biochemical, immuno-cytochemistry and electron microscopy techniques. Different in silico analyses revealed that TCLP 1 is the founding member of a family of chimeric molecules restricted to trypanosomatids bearing, in addition to eukaryotic ubiquitin-like and protein-protein interacting domains, a motif displaying significant structural homology to bacterial multi-cargo chaperones involved in the secretion of virulence factors.

Using the fidelity of an homologous expression system we confirmed TCLP 1 sub-cellular distribution and showed that TCLP 1-over-expressing parasites display impaired survival and accelerated progression to late stationary phase under starvation conditions. The reduced endocytic capacity of TCLP 1-over-expressors likely underlies at least in part this growth phenotype.

TCLP 1 is involved in the uptake of extracellular macromolecules required for nutrition and hence in T. Due to the bacterial origin, sub-cellular distribution and putative function s, we propose TCLP 1 and related orthologs in trypanosomatids as appealing therapeutic targets for intervention against these health-threatening parasites. The flagellar pocket constitutes an active and strategic site in the body of trypanosomatids i. Due to the bacterial origin, sub-cellular distribution and putative function s , we propose TCLP 1 and related orthologs in trypanosomatids as appealing therapeutic targets for intervention against these health-threatening parasites.

Type III secretion systems T3SSs are multiprotein molecular devices used by many Gram-negative bacterial pathogens to translocate effector proteins into eukaryotic cells.

A T3SS is also used for protein export in flagellar assembly, which promotes bacterial motility. The two systems are evolutionarily related, possessing highly conserved components in their export apparatuses. Its highly regulated movement is essential for the normal function of many organs; ciliopathies cause congenital defects, chronic respiratory tract infections and infertility.

We present an efficient method to obtain a quantitative description of flagellar motion, with high spatial and temporal resolution, from high speed video recording of bright field images.

This highly automated tec Direct evidence of flagellar synchronization through hydrodynamic interactions. Eukaryotic cilia and flagella exhibit striking coordination, from the synchronous beating of two flagella in Chlamydomonas to the metachronal waves and large-scale flows displayed by carpets of cilia. However, the precise mechanisms responsible for flagellar synchronization remain unclear.

We perform a series of experiments involving two individual flagella in a quiescent fluid. Cells are isolated from the colonial alga Volvox carteri, held in place at a fixed distance d, and oriented so that their flagellar beating planes coincide.

In this fashion, we are able to explicitly assess the role of hydrodynamics in achieving synchronization. For closely separated cells, the flagella are capable of exhibiting a phase-locked state for thousands of beats at a time, despite significant differences in their intrinsic frequencies.

The coupling strength extracted through analysis of the synchronization statistics exhibits excellent agreement with hydrodynamic predictions.

This study unambiguously reveals that flagella coupled only through hydrodynamics are capable of exhibiting robust synchrony. Probing flagellar promoter occupancy in wild-type and mutant Caulobacter crescentus by chromatin immunoprecipitation.

In the asymmetric predivisional cell of Caulobacter crescentus, TipF and TipN mark the cellular pole for future flagellar development. TipN is localized to the flagellar pole before TipF and is essential for the proper placement of the flagellum in C. We deduce that TipF contributes to proper expression of flagellar genes in C. Second-chance signal transduction explains cooperative flagellar switching. Full Text Available The reversal of flagellar motion switching results from the interaction between a switch complex of the flagellar rotor and a torque-generating stationary unit, or stator motor unit.

To explain the steeply cooperative ligand-induced switching, present models propose allosteric interactions between subunits of the rotor, but do not address the possibility of a reaction that stimulates a bidirectional motor unit to reverse direction of torque.

During flagellar motion, the binding of a ligand-bound switch complex at the dwell site could excite a motor unit. The probability that another switch complex of the rotor, moving according to steady-state rotation, will reach the same dwell site before that motor unit returns to ground state will be determined by the independent decay rate of the excited-state motor unit.

Here, we derive an analytical expression for the energy coupling between a switch complex and a motor unit of the stator complex of a flagellum, and demonstrate that this model accounts for the cooperative switching response without the need for allosteric interactions. The analytical result can be reproduced by simulation when 1 the motion of the rotor delivers a subsequent ligand-bound switch to the excited motor unit, thereby providing the excited motor unit with a second chance to remain excited, and 2 the outputs from multiple independent motor units are constrained to a single all-or-none event.

In this proposed model, a motor unit and switch complex represent the components of a mathematically defined signal transduction mechanism in which energy coupling is driven by steady-state and is regulated by stochastic ligand binding.

Mathematical derivation of the model shows the analytical function to be a general form of the Hill equation Hill AV The possible effects of the aggregation of the molecules of haemoglobin on its dissociation curves.

Bioconvection is a form of collective motion that occurs spontaneously in the suspension of swimming microorganisms. In a previous study, we quantitatively described the "pattern transition," a phase transition phenomenon that so far has exclusively been observed in bioconvection of the unicellular green alga Chlamydomonas.

We suggested that the transition could be induced by changes in the balance between the gravitational and shear-induced torques, both of which act to determine the orientation of the organism in the shear flow. As both of the torques should be affected by the geometry of the Chlamydomonas cell, alteration in the flagellar waveform might change the extent of torque generation by altering overall geometry of the cell. Based on this working hypothesis, we examined bioconvection behavior of two flagellar mutants of Chlamydomonas reinhardtii, ida1 and oda2, making reference to the wild type.

Flagella of ida1 beat with an abnormal waveform, while flagella of oda2 show a normal waveform but lower beat frequency. Two-axis view revealed the periodic movement of the settling blobs of ida1, while oda2 showed qualitatively similar behavior to that of wild type. Unexpectedly, ida1 showed stronger negative gravitaxis than did wild type, while oda2 showed relatively weak gravitaxis.

These findings suggest that flagellar waveform, not swimming speed or beat frequency, strongly affect bioconvection behavior in C. Optimization of flagellar swimming by a model sperm.

The swimming of a bead-spring chain in a viscous incompressible fluid as a model of a sperm is studied in the framework of low Reynolds number hydrodynamics. The optimal mode in the class of planar flagellar strokes of small amplitude is determined on the basis of a generalized eigenvalue problem involving two matrices which can be evaluated from the mobility matrix of the set of spheres constituting the chain.

For an elastic chain with a cargo constraint for its spherical head, the actuating forces yielding a nearly optimal stroke can be determined. These can be used in a Stokesian dynamics simulation of large amplitude swimming.

Biochemical characterization of tektins from sperm flagellar doublet microtubules. Tektins, protein components of stable protofilaments from sea urchin sperm flagellar outer doublet microtubules Linck, R. Only three types of electrically driven rotary motors exist in nature: This pattern was confirmed in swimming assays of stator-less Bacillus subtilis and Escherichia coli mutants expressing MotPS from B. The finding will affect the understanding of the operating principles of flagellar motors and the molecular mechanisms of ion selectivity, the field of the evolution of environmental changes and stresses, and areas of nanotechnology.

Modulation of Chlamydomonas reinhardtii flagellar motility by redox poise. Redox-based regulatory systems are essential for many cellular activities. Chlamydomonas reinhardtii exhibits alterations in motile behavior in response to different light conditions photokinesis. We hypothesized that photokinesis is signaled by variations in cytoplasmic redox poise resulting from changes in chloroplast activity.

Analysis of reactivated cell models revealed that this redox poise effect is mediated through the outer dynein arms ODAs. These data indicate that redox poise directly affects ODAs and suggest that it may act in the control of flagellar motility. Marine bacterium Vibrio alginolyticus uses a single polar flagellum to navigate in an aqueous environment. Similar to Escherichia coli cells, the polar flagellar motor has two states; when the motor is counter-clockwise, the cell swims forward and when the motor is clockwise, the cell swims backward.

The short-time inhibition is sufficiently strong and long lasting, i. Structure of the microtubule-binding domain of flagellar dynein. Flagellar dyneins are essential microtubule motors in eukaryotes, as they drive the beating motions of cilia and flagella.

Unlike myosin and kinesin motors, the track binding mechanism of dyneins and the regulation between the strong and weak binding states remain obscure. The flap is positively charged and highly flexible.

Despite the structural similarity to cytoplasmic MTBD, dynein-c MTBD shows only a small change in the microtubule- binding affinity depending on the registry change of coiled coil-sliding, whereby lacks the apparent strong binding state. The surface charge distribution of dynein-c MTBD also differs from that of cytoplasmic MTBD, which suggests a difference in the microtubule-binding mechanism. Campylobacter jejuni is a causative pathogen of human acute bacterial gastroenteritis. Infected poultry products are regarded as a major source for human C.

The flagellar capping protein FliD is highly conserved among C. In this study, we used the FliD protein as a probe to survey the prevalence of C. Iron transport across the outer membrane is an energydependent process that relies on the electrochemical potential PMF, proton motif force of the inner membrane and the energy transduction complex TonBExbB-ExbD [4]. In the acidic growth environment of A. TonB appears to shuttle between the cytoplasmic and outer membranes, extracting the ligand from the OMRs and passing it to a cytoplasmic metal binding protein.

There are six putative candidate TonB-class proteins predicted in the A. Given that this central domain appears to be important for the ability of TonB to bridge the periplasmic space by allowing TonB to adopt a rigid extended conformation [36], these substitutions could represent a functional adaptation of the TonB of A. Heteromultimers of ExbB and ExbD are thought to constitute a proton-translocating unit. Both proteins are anchored in the inner membrane and predicted inner membrane embedded loops of the putative ExbB and ExbD of A.

There are also crystal structures at 1. All ABC-transporter components, including those with domains in the periplasm, are highly conserved with respect to neutrophilic counterparts.

General primary sequence conservation of these components further supports that a predicted mechanism of siderophore uptake similar to those found in other organisms accumulating Fe III in iron-poor conditions may exist in A. Some of these clusters include other genes known to be involved in iron transport clusters A, B , whereas others contain genes that participate in diverse metal-homeostasis responses clusters C, E.

The remaining siderophore OMRs detected in A. The organization of iron uptake functions in operons, or forming part of pathogenicity islands, is frequent in bacteria. However, the presence of several siderophore OMRs in the same gene cluster is not as frequent [53].

Clusters A and B both include the predicted genes exbB, exbD and tonB for the TonB energy-transducing system, but cluster B also contains three candidate genes for periplasmic metal binding proteins and genes that potentially encode an ABC-type inner membrane iron transporter.

Interestingly, this possible operon also includes a putative gene for a globin-like protein of unknown function and an upstream Fur box, indicating possible regulation via a Fur-mediated mechanism. The genetic proximity of these systems with Fe III -siderophore OMRs may indicate cross-talk between metal transporting systems at the inner membrane level. The close proximity of two OMRs of A.

Conclusions Bioinformatic genome analysis for iron uptake, sensing, storage and regulation provides an initial framework for addressing how A. The multiple siderophore uptake systems found in A. So far, only the role of Fur from A. The modeling presented here will also enable researchers to identify possible regulatory connections required for the coordinated control of the components involved in balancing the requirements of iron as a nutrient in very small amounts versus its use as an energy and electron source in much larger amounts.

Acknowledgements This work is supported by Fondecyt No. Sequencing of the A. Braun V, Killmann H Bacterial solutions to the ironsupply problem. Trends Biochem Sci Nat Struct Biol 4: Nat Struct Biol 6: J Biol Chem Nat Struct Biol 7: Crosa JH Signal transduction and transcriptional and posttranscriptional control of iron-regulated genes in bacteria. Microbiol Mol Biol Rev Appl Environ Microbiol Hantke K Ferrous iron uptake by a magnesium transport system is toxic for Escherichia coli and Salmonella typhimurium.

Hantke K Iron and metal regulation in bacteria. Curr Opin Microbiol 4: Hantke K, Braun V The art of keeping low and high iron concentrations in balance. ASM, New York, pp — ExbB and ExbD form homomultimers.

Int J Syst Evol Microbiol IrgA is not required for virulence. Appl Microbiol Biotechnol Postle K TonB protein and energy transduction between membranes. J Bioenerg Biomembr Rawlings DE Heavy metal mining using microbes. Annu Rev Microbiol Touati D Iron and oxidative stress in bacteria.

Affinities and in-plane stress forces between glycopeptide antibiotics and biomimetic bacterial membranes. Full Text Available Understanding the molecular basis of interactions between antibiotics affecting bacterial cell wall biosynthesis and cellular membranes is important in rational drug design of new drugs to overcome resistance.

However, a precise understanding of how bacteriostatic antibiotics effect action often neglects the effect of biophysical forces involved following antibiotic-receptor binding events.

We have employed a combination of a label-free binding biosensor surface plasmon resonance, SPR and a force biosensor in-plane stress cantilever, together with model membrane systems to study the complex interplay between glycopeptide antibiotics, their cognate ligands and different model membranes. Binding affinities and kinetics of the antibiotics to these model membranes were influenced by electrostatic interactions with the different lipid backgrounds, in addition to ligand affinities.

In addition, cantilever sensors coated with model membranes showed that planar surface stress changes were induced by glycopeptide antibiotics adsorption and caused compressive surface stress generation in a ligand-dependent manner.

Bacterial cellulose membrane as flexible substrate for organic light emitting devices. In order to achieve the necessary conductive properties indium tin oxide ITO thin films were deposited onto the membrane at room temperature using radio frequency r. Resistivity, mobility and carrier concentration of deposited ITO films were 4. In order to demonstrate the feasibility of devices based on BC membranes three OLEDs with different substrates were produced: The observed OLED luminance ratio was: These preliminary results show clearly that the functionalized biopolymer, biodegradable, biocompatible bacterial cellulose membranes can be successfully used as substrate in flexible organic optoelectronic devices.

Adaptations of archaeal and bacterial membranes to variations in temperature, pH and pressure. The cytoplasmic membrane of a prokaryotic cell consists of a lipid bilayer or a monolayer that shields the cellular content from the environment. In addition, the membrane contains proteins that are responsible for transport of proteins and metabolites as well as for signalling and energy transduction. Maintenance of the functionality of the membrane during changing environmental conditions relies on the cell's potential to rapidly adjust the lipid composition of its membrane.

Despite the fundamental chemical differences between bacterial ester lipids and archaeal ether lipids, both types are functional under a wide range of environmental conditions. We here provide an overview of archaeal and bacterial strategies of changing the lipid compositions of their membranes.

Some molecular adjustments are unique for archaea or bacteria, whereas others are shared between the two domains. Strikingly, shared adjustments were predominantly observed near the growth boundaries of bacteria. Here, we demonstrate that the presence of membrane spanning ether-lipids and methyl branches shows a striking relationship with the growth boundaries of archaea and bacteria.

Recombinant Expression Screening of P. However, much less is known about their structures and molecular mechanisms than for soluble proteins. Problems in expression, solubilization, purification, and crystallization cause bottlenecks in the characterization of TM proteins. This project addressed the need for improved methods for obtaining sufficient amounts of TM proteins for determining their structures and molecular mechanisms. Results Plasmid clones were obtained that encode eighty-seven transmembrane proteins with varying physical characteristics, for example, the number of predicted transmembrane helices, molecular weight, and grand average hydrophobicity GRAVY.

All the target proteins were from P. The relative expression levels of the transmembrane proteins were measured under several culture growth conditions.

The use of E. In this study, proteins with a higher grand average hydrophobicity and more transmembrane helices were expressed less well than less hydrophobic proteins with fewer transmembrane helices.

Conclusions In this study, factors related to overall hydrophobicity and the number of predicted transmembrane helices correlated with the relative expression levels of the target proteins. Identifying physical characteristics that correlate with protein expression might aid in selecting the "low hanging fruit", or proteins that can be expressed to sufficient levels using an E.

The use of other expression strategies or host species might be needed for sufficient levels of expression of transmembrane proteins with other physical. Electrochemical characterization of pore formation by bacterial protein toxins on hybrid supported membranes. The interaction of pore-forming streptolysin O SLO with biomimetic lipid membranes has been studied by electrochemical methods.

Phosphatidylcholine lipid vesicles were deposited onto gold electrodes modified with supporting layers of hexyl thioctate HT or thioctic acid tri ethylene glycol ester TA-TEGE , and integrity and permeability of the resulting membranes were characterized by cyclic voltammetry and impedance spectroscopy. Both positively and negatively charged electrochemical probes, potassium ferrocyanide, hexaammineruthenium III chloride, and ferrocene carboxylic acid FCA , were employed to evaluate their suitability to probe the membrane permeability properties, with FCA exhibiting ideal behavior and thus employed throughout the work.

The interaction of SLO with preformed supported lipid membranes was also investigated, and much lower response was observed, suggesting a different extent of membrane -toxin interactions on such an interface.

Nonionic surfactant Triton was found to disrupt the vesicle structure but could not completely remove a preformed membrane to fully restore the electrode response. The information reported here offers some unique insight into toxin-surface interactions on a hybrid membrane , facilitating the development of electrochemically based sensing platforms for detecting trace amounts of bacterial toxins via the perforation process.

Bacterial origin of a mitochondrial outer membrane protein translocase: Mitochondria are of bacterial ancestry and have to import most of their proteins from the cytosol. This process is mediated by Tom40, an essential protein that forms the protein-translocating pore in the outer mitochondrial membrane.

Tom40 is conserved in virtually all eukaryotes, but its evolutionary origin is unclear because bacterial orthologues have not been identified so far. Recently, it was shown that the parasitic protozoon Trypanosoma brucei lacks a conventional Tom40 and instead employs the archaic translocase of the outer mitochondrial membrane ATOM , a protein that shows similarities to both eukaryotic Tom40 and bacterial protein translocases of the Omp85 family. Here we present electrophysiological single channel data showing that ATOM forms a hydrophilic pore of large conductance and high open probability.

Moreover, ATOM channels exhibit a preference for the passage of cationic molecules consistent with the idea that it may translocate unfolded proteins targeted by positively charged N-terminal presequences. This is further supported by the fact that the addition of a presequence peptide induces transient pore closure. An in-depth comparison of these single channel properties with those of other protein translocases reveals that ATOM closely resembles bacterial -type protein export channels rather than eukaryotic Tom Our results support the idea that ATOM represents an evolutionary intermediate between a bacterial Omplike protein export machinery and the conventional Tom40 that is found in mitochondria of other eukaryotes.

Guanidino groups greatly enhance the action of antimicrobial peptidomimetics against bacterial cytoplasmic membranes. Antimicrobial peptides or their synthetic mimics are a promising class of potential new antibiotics. Herein we assess the effect of the type of cationic side chain i. We found guanidino group-containing chimeras Surface physical chemistry properties in coated bacterial cellulose membranes with calcium phosphate. Bacterial cellulose has become established as a new biomaterial, and it can be used for medical applications.

In addition, it has called attention due to the increasing interest in tissue engineering materials for wound care. In this work, the bacterial cellulose fermentation process was modified by the addition of chondroitin sulfate to the culture medium before the inoculation of the bacteria. The biomimetic process with heterogeneous calcium phosphate precipitation of biological interest was studied for the guided regeneration purposes on bacterial cellulose.

XTT results concluded that these materials did not affect significantly in the cell viability, being non-cytotoxic. Thus, it was produced one biomaterial with the surface charge changes for calcium phosphate deposition, besides different wettability which builds new membranes for Guided Tissue Regeneration.

Full Text Available Human amniotic membrane is considered a promising allograft material for the treatment of ocular surface reconstruction, burns, and other skin defects. In order to avoid the transmission of any diseases, grafts should be perfectly sterile.

Twenty-five amniotic sacs were collected to determine the microbiological quality of human amniotic membrane , to analyze the radiation sensitivity pattern of the microorganism, and to detect the radiation decimal reduction dose D10 values.

All the samples were found to be contaminated, and the bioburden was ranged from 3. The results depict gradual decline in bioburden with incline of radiation doses. The D10 values of the bacterial isolates were ranged from 0.

To compare the differences, D10 values were also calculated by graphical evaluations of the data with two of the representative isolates of each bacterial species which showed no significant variations. Findings of this study indicate that lower radiation dose is quite satisfactory for the sterilization of amniotic membrane grafts. Therefore, these findings would be helpful to predict the efficacy of radiation doses for the processing of amniotic membrane for various purposes. Human amniotic membrane is considered a promising allograft material for the treatment of ocular surface reconstruction, burns, and other skin defects.

Predominant membrane localization is an essential feature of the bacterial signal recognition particle receptor. Strikingly, although FtsY requires membrane contact for functionality, cell fractionation studies have localized FtsY predominantly to the cytosolic fraction of Escherichia coli.

So far, the exact function of the soluble SR in E. Results In the current study we have determined the contribution of soluble FtsY to co-translational targeting in vitro and have re-analysed the localization of FtsY in vivo by fluorescence microscopy.

These data show that soluble FtsY does not contribute significantly to cotranslational targeting in E. In agreement with this observation, our in vivo analyses of FtsY localization in bacterial cells by fluorescence microscopy revealed that the vast majority of FtsY was localized to the inner membrane and that soluble FtsY constituted only a negligible species in vivo.

Our data show that the bacterial SR is. Secretion of bacterial lipoproteins: Bacterial lipoproteins are peripherally anchored membrane proteins that play a variety of roles in bacterial physiology and virulence in monoderm single membrane -enveloped, e. After export of prolipoproteins through the cytoplasmic membrane , which occurs predominantly but not exclusively via the general secretory or Sec pathway, the proteins are lipid-modified at the cytoplasmic membrane in a multistep process that involves sequential modification of a cysteine residue and cleavage of the signal peptide by the signal II peptidase Lsp.

In both monoderms and diderms, signal peptide processing is preceded by acylation with a diacylglycerol through preprolipoprotein diacylglycerol transferase Lgt. In diderms but also some monoderms, lipoproteins are further modified with a third acyl chain through lipoprotein N-acyl transferase Lnt. Fully modified lipoproteins that are destined to be anchored in the inner leaflet of the outer membrane OM are selected, transported and inserted by the Lol lipoprotein outer membrane localization pathway machinery, which consists of the inner- membrane IM ABC transporter-like LolCDE complex, the periplasmic LolA chaperone and the OM LolB lipoprotein receptor.

Surface localization of lipoproteins in diderms is rare in most bacteria, with the exception of several spirochetal species. In the model spirochete Borrelia burgdorferi, surface lipoprotein secretion does not follow established sorting rules, but remains dependent on N-terminal peptide sequences.

Secretion through the outer membrane requires maintenance of lipoproteins in a translocation-competent unfolded conformation. Effects of structure on the interactions between five natural antimicrobial compounds and phospholipids of bacterial cell membrane on model monolayers.

Monolayers composed of bacterial phospholipids were used as model membranes to study interactions of naturally occurring phenolic compounds 2,5-dihydroxybenzaldehyde, 2-hydroxymethoxybenzaldehyde and the plant essential oil compounds carvacrol, cinnamaldehyde, and geraniol, previously found to be Enriched glucose and dextrin mannitol-based media modulates fibroblast behavior on bacterial cellulose membranes.

Bacterial cellulose BC produced by Gluconacetobacter hansenii is a suitable biopolymer for biomedical applications. In order to modulate the properties of BC and expand its use as substrate for tissue engineering mainly in the form of biomembranes, glucose or dextrin were added into a BC fermentation mannitol-based medium BCGl and BCDe, respectively under static culture conditions.

SEM images showed effects on fiber density and porosity on both sides of the BC membranes. Both enriched media decreased the BET surface area, water holding capacity, and rehydration rate. L fibroblast cells were seeded on all BC-based membranes and evaluated in aspects of cell adhesion, proliferation and morphology. BCG1 membranes showed the highest biological performance and hold promise for the use in tissue engineering applications. Production of bacterial cellulose membranes in a modified airlift bioreactor by Gluconacetobacter xylinus.

In this study, a novel bioreactor for producing bacterial cellulose BC is proposed. Traditional BC production uses static culture conditions and produces a gelatinous membrane. The potential for using various types of bioreactor, including a stirred tank, conventional airlift, and modified airlift with a rectangular wire-mesh draft tube, in large-scale production has been investigated. The BC obtained from these bioreactors is fibrous or in pellet form.

Our proposed airlift bioreactor produces a membrane -type BC from Gluconacetobacter xylinus, the water-holding capacity of which is greater than that of cellulose types produced using static cultivation methods.

The Young's modulus of the product can be manipulated by varying the number of net plates in the modified airlift bioreactor. The BC membrane produced using the proposed bioreactor exhibits potential for practical application.

Freestanding bacterial cellulose-graphene oxide composite membranes with high mechanical strength for selective ion permeation. Graphene oxide GO based membranes have been widely applied in molecular separation based on the size exclusion effect of the nanochannels formed by stacked GO sheets. Here, a freestanding composite membrane based on bacterial cellulose BC and GO is designed and prepared.

Therefore, this novel composite membrane is considered to be a promising candidate in the applications of water purification, food industry, biomedicine, and pharmaceutical and fuel separation. Altering the thermal resistance of foodborne bacterial pathogens with an eggshell membrane waste by-product.

Eggshells from egg-breaking operations are a significant waste disposal problem. Thus, the development of value-added by-products from this waste would be welcomed by the industry. The ability of extracted eggshell membranes containing, several bacteriolytic enzymes i. Following exposure, membrane -free samples 1. Population reductions ranging from D-value reductions ranging from 0 LM to The effects of exposure pH, time, temperature, and organic load on membrane activity were also evaluated with Salmonella Typhimurium.

However, the presence of organic matter 0. These preliminary findings provide information on the potential use of extracted eggshell. A bilayer-couple model of bacterial outer membrane vesicle biogenesis. Gram-negative bacteria naturally produce outer membrane vesicles OMVs that arise through bulging and pinching off of the outer membrane.

OMVs have several biological functions for bacteria, most notably as trafficking vehicles for toxins, antimicrobials, and signaling molecules. While their biological roles are now appreciated, the mechanism of OMV formation has not been fully elucidated. We hypothesized that PQS stimulates OMV formation through direct interaction with the outer leaflet of the outer membrane. To test this hypothesis, we employed a red blood cell RBC model that has been used extensively to study small-molecule- membrane interactions.

Our results revealed that addition of PQS to RBCs induced membrane curvature, resulting in the formation of membrane spicules spikes , consistent with small molecules that are inserted stably into the outer leaflet of the membrane. Radiotracer experiments demonstrated that sufficient PQS was inserted into the membrane to account for this curvature and that curvature induction was specific to PQS structure. These data suggest that a low rate of interleaflet flip-flop forces PQS to accumulate in and expand the outer leaflet relative to the inner leaflet, thus inducing membrane curvature.

In support of PQS-mediated outer leaflet expansion, the PQS effect was antagonized by chlorpromazine, a molecule known to be preferentially inserted into the inner leaflet. Based on these data, we propose a bilayer-couple model to describe P. Despite the ubiquity and importance of outer membrane vesicle OMV production in Gram-negative bacteria, the molecular details of OMV biogenesis are not fully understood.

The membranes are based on blending bacterial nanocellulose pulp and Nafion abbreviated as BxNy, where x and y indicates the mass ratio of bacterial cellulose to Nafion. It is found that the BxNy composite membranes with reinforced concrete-like structure show excellent mechanical and thermal stability regardless of annealing.

The water uptake plus area and volume swelling ratios are all decreased compared to Nafion membranes. The proton conductivities of pristine and annealed B1N9 are 0. Specifically, annealed B1N1 exhibited the lowest methanol permeability of 7. The performances of the pristine and annealed B1N7 reach a level as high as Translocation of dPNAG across the bacterial outer membrane is mediated by a tetratricopeptide repeat-containing outer membrane protein, PgaA.

To understand the molecular basis of dPNAG translocation, we determined the crystal structure of the C-terminal transmembrane domain of PgaA residues Half of the interior surface of the barrel that lies parallel to the translocation pathway is electronegative, suggesting that the corresponding negatively charged residues may assist the secretion of the positively charged dPNAG polymer.

In vivo complementation assays in a pgaA deletion bacterial strain showed that a cluster of negatively charged residues proximal to the periplasm is necessary for biofilm formation. Biochemical analyses further revealed that the tetratricopeptide repeat domain of PgaA binds directly to the N-deacetylase PgaB and is critical for biofilm formation. Antimicrobial Nanoplexes meet Model Bacterial Membranes: Antimicrobial resistance to traditional antibiotics is a crucial challenge of medical research.

Oligonucleotide therapeutics, such as antisense or Transcription Factor Decoys TFDs , have the potential to circumvent current resistance mechanisms by acting on novel targets. However, their full translation into clinical application requires efficient delivery strategies and fundamental comprehension of their interaction with target bacterial cells.

To address these points, we employed a novel cationic bolaamphiphile that binds TFDs with high affinity to form self-assembled complexes nanoplexes. Confocal microscopy revealed that nanoplexes efficiently transfect bacterial cells, consistently with biological efficacy on animal models. To understand the factors affecting the delivery process, liposomes with varying compositions, taken as model synthetic bilayers, were challenged with nanoplexes and investigated with Scattering and Fluorescence techniques.

Thanks to the combination of results on bacteria and synthetic membrane models we demonstrate for the first time that the prokaryotic-enriched anionic lipid Cardiolipin CL plays a key-role in the TFDs delivery to bacteria.

Moreover, we can hypothesize an overall TFD delivery mechanism, where bacterial membrane reorganization with permeability increase and release of the TFD from the nanoplexes are the main factors. These results will be of great benefit to boost the development of oligonucleotides-based antimicrobials of superior efficacy.

Bacterial reaction centers purified with styrene maleic acid copolymer retain native membrane functional properties and display enhanced stability. Antoinette; Jones, Michael R. Integral membrane proteins often present daunting challenges for biophysical characterization, a fundamental issue being how to select a surfactant that will optimally preserve the individual structure and functional properties of a given membrane protein.

Bacterial reaction centers offer a rare opp. Production and characterization of bacterial cellulose membranes with hyaluronic acid from chicken comb. The bacterial cellulose BC , from Gluconacetobacter hansenii, is a biofilm with a high degree of crystallinity that can be used for therapeutic purposes and as a candidate for healing wounds. Hyaluronic acid HA is a constitutive polysaccharide found in the extracellular matrix and is a material used in tissue engineering and scaffolding for tissue regeneration.

The structural characteristics, thermal stability and molar mass of hyaluronic acid from chicken comb were evaluated. Native membrane and polymeric composites were characterized with respect to their morphology and crystallinity. The optimized process of extraction and purification of hyaluronic acid resulted in low molar mass hyaluronic acid with structural characteristics similar to the standard commercial hyaluronic acid.

The membranes produced on the third day presented better incorporation of HA-SAB between cellulose microfiber, resulting in membranes with higher thermal stability, higher roughness and lower crystallinity. The biocompatiblily of bacterial cellulose and the importance of hyaluronic acid as a component of extracellular matrix qualify the polymeric composites as promising biomaterials for tissue engineering.

Full Text Available To improve the efficacy and safety of dural repair in neurosurgical procedures, a new dural material derived from bacterial cellulose BC was evaluated in a rabbit model with dural defects. We prepared artificial dura mater using bacterial cellulose which was incubated and fermented from Acetobacter xylinum. The dural defects of the rabbit model were repaired with BC membranes. All surgeries were performed under sodium pentobarbital anesthesia, and all efforts were made to minimize suffering.

All animals were humanely euthanized by intravenous injection of phenobarbitone, at each time point, after the operation. Then, the histocompatibility and inflammatory effects of BC were examined by histological examination, real-time fluorescent quantitative polymerase chain reaction PCR and Western Blot. BC membranes evenly covered the surface of brain without adhesion. There were seldom inflammatory cells surrounding the membrane during the early postoperative period.

BC can repair dural defects in rabbit and has a decreased inflammatory response compared to traditional materials. However, the long-term effects need to be validated in larger animals. The participation of outer membrane proteins in the bacterial sensitivity to nanosilver.

The presented study is to analyze the participation of outer membrane proteins of Gram- negative bacteria in sensitivity to silver nanomaterials. The mechanism of interaction of silver with the bacterial cell is best described in this group of microorganisms.

There are several theories regarding the effectiveness of antimicrobial ions and nanosilver, and at the indicated differences in the way they work. Outer membrane proteins of Gram-negative bacteria are involved in the procurement of silver from the environment and contribute to the development mechanisms of resistance to nanometals.

They are measurable parameter in the field of cell phenotypic response to the presence of Gram-negative bacteria in the environment silver nanoforms: During the very fast nanotechnology developing and introduction to the market products based on the nanosilver the bacterial answer to nanosilver is needed.

Interspecies communication between pathogens and immune cells via bacterial membrane vesicles. Full Text Available The production of extracellular vesicles is a universal mechanism for intercellular communication that is conserved across kingdoms. Prokaryotes secrete 50— nm membrane vesicles MVs in a manner that is regulated by environmental stress and is thought to promote survival.

Since many types of host-derived stress are encountered during infection, this implies an important role for MV secretion in bacterial pathogenesis. Accordingly, MVs produced by gram-positive and gram-negative pathogens contain toxins, virulence factors, and other molecules that promote survival in the host. However, recent studies have also shown that bacterial MVs are enriched for molecules that stimulate innate and adaptive immune responses.

As an example, MVs may serve multiple, important roles in regulating the host response to Mycobacterium tuberculosis Mtb, an intracellular pathogen that infects lung macrophages and resides within modified phagosomes.

Previously, we demonstrated that Mtb secretes MVs during infection that may regulate infected and uninfected immune cells. We conclude that bacterial MVs serve dual and opposing roles in the activation of and defense against host immune responses to Mtb and other bacterial pathogens.

We also propose that MV secretion is a central mechanism for interspecies communication between bacteria and host cells during infection. Bacterial outer membrane vesicle biogenesis: First considered as a by-product of cell lysis, it soon became evident that OMVs are actively secreted from the outer membrane OM of Gram-negative bacteria.

However, OMVs may also comprise periplasmic, inner membrane , or cytoplasmic components. Since the shedding of substantial amounts of OM material represents a significant energy cost to the bacterial cell, OMV production must have some vital biological functions for Gram-negative bacteria.

Indeed, intense research on that topic revealed that OMVs play important roles in bacterial physiology and pathogenesis, ranging from secretion and delivery of biomolecules for example, toxins, DNA, or quorum sensing molecules over stress response and biofilm formation to immunomodulation and adherence to host cells. Only recently researchers have begun to elucidate the mechanistic aspects of OMV formation, but a general mechanism for the biogenesis of these vesicles is still lacking.

Here we review the findings and implications of our recent study published in Nature Communications Roier S, et al. This mechanism might not only have important pathophysiological roles in vivo, but also represents the first general mechanism of OMV formation applicable to all Gram-negative bacteria.

Outer membrane vesicle OMV release by Gram-negative bacteria has been observed and studied for decades. Full Text Available Aggregatibacter actinomycetemcomitans is a gram-negative opportunistic oral pathogen. We have recently shown that this cytokine localizes to the cytoplasm of A. In this study, we characterized the interaction of A. The interacting protein, which we have designated bacterial interleukin receptor I BilRI, was identified through mass spectrometry and was found to be Pasteurellaceae specific.

Based on the results obtained using protein function prediction tools, this protein localizes to the outer membrane and contains a typical lipoprotein signal sequence. All six tested biofilm cultures of clinical A. Moreover, proteinase K treatment of whole A. The protein was overexpressed in Escherichia coli in both the outer membrane -associated form and a soluble cytoplasmic form. When assessed using flow cytometry, the BilRI-overexpressing E.

Overexpression of BilRI did not cause binding of a biotinylated negative control protein. Outer membrane vesicles OMVs are spherical nanostructures that are ubiquitously shed from gram-negative bacteria both in vitro and in vivo. Recent findings revealed that OMVs, which contain diverse components derived from the parent bacterium, play an important role in communication with neighboring bacteria and the environment.

Furthermore, nanoscale proteoliposomes decorated with pathogen-associated molecules attract considerable attention as a non-replicative carrier for vaccines and drug materials.

This review introduces recent advances in OMV biogenesis and discusses the roles of OMVs in the context of bacterial communication and virulence regulation.

It also describes the remarkable accomplishments in OMV engineering for diverse therapeutic applications. Influence of the physical state of the bacterial cell membrane upon the rate of respiration. Cell-free enzymes concerned in respiration and prepared from the same organisms are not inhibited by these salts, whereas these same enzymes tested in intact cells are.

The physical state of the cell membrane appears to be a factor controlling its respiratory activity. Explosive cell lysis as a mechanism for the biogenesis of bacterial membrane vesicles and biofilms. Many bacteria produce extracellular and surface-associated components such as membrane vesicles MVs , extracellular DNA and moonlighting cytosolic proteins for which the biogenesis and export pathways are not fully understood.

Here we show that the explosive cell lysis of a sub-population of cells accounts for the liberation of cytosolic content in Pseudomonas aeruginosa biofilms. Super-resolution microscopy reveals that explosive cell lysis also produces shattered membrane fragments that rapidly form MVs. A prophage endolysin encoded within the R- and F-pyocin gene cluster is essential for explosive cell lysis.

Endolysin-deficient mutants are defective in MV production and biofilm development, consistent with a crucial role in the biogenesis of MVs and liberation of extracellular DNA and other biofilm matrix components. Our findings reveal that explosive cell lysis, mediated through the activity of a cryptic prophage endolysin, acts as a mechanism for the production of bacterial MVs.

Connective tissue and bacterial deposits on rubber dam sheet and ePTFE barrier membranes in guided periodontal tissue regeneration. The aim of this study was to compare the connective tissue and bacterial deposits on rubber dam sheets and expanded polytetrafluoroethylene membranes used as barrier membranes in guided tissue regeneration for periodontal treatment.

Four to six weeks after the first operation, membranes were retrieved from the lesion sites and processed for scanning electron microscopy.

The lesion-facing surfaces of membranes were examined for the presence of connective tissue and bacterial deposits. The differences between the numbers of fields and the distributions of connective tissue and bacteria on both types of membranes were analysed by the Chi-square test at the level of 0.

The results showed a lot of fibroblasts with their secreted extracellular matrices, known as components of the connective tissue on rubber dam sheets and expanded polytetrafluoroethylene membranes. Many bacterial forms including cocci, bacilli, filaments and spirochetes with the interbacterial matrices were identified.

The total number of bacteria on rubber dam sheets was statistically less than that on expanded polytetrafluoroethylene membranes P tissue on both types of membranes suggests that the healing process under both types of membranes was also comparable.

Therefore, the rubber dam sheet might be used as a barrier membrane in guided tissue regeneration.

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The histidine kinase senses an environmental signal, which it transmits to its partner response regulator via a series of autophosphorylation, phosphotransfer, and dephosphorylation reactions. Much work has been done on particular systems , including several systems with regulatory roles in cellular physiology, communication, development, and, in the case of bacterial pathogens, the expression of genes important for virulence. We used two methods to investigate two-component regulatory systems in Escherichia coli K First, we systematically constructed mutants with deletions of all two-component systems by using a now-standard technique of gene disruption K.

We then analyzed these deletion mutants with a new technology called Phenotype MicroArrays, which permits assays of nearly 2, growth phenotypes simultaneously. The results of this battery of nearly , tests provided a wealth of new information concerning many of these systems. Of 37 different two-component mutants, 22 showed altered phenotypes. Many phenotypes were expected, and several new phenotypes were also revealed.

The results are discussed in terms of the biological roles and other information concerning these systems , including DNA microarray data for a large number of the same mutants. Other mutational effects are also discussed. Two-component systems are signal transduction systems which enable bacteria to regulate cellular functions in response to changing environmental conditions.

The unicellular Synechocystis sp. PCC has become a model organism for a range of biochemical and molecular biology studies aiming at investigating environmental stress response.

The publication of the complete genome sequence of the cyanobacterium Synechocystis sp. PCC provided a tremendous stimulus for research in this field, and at least 80 open reading frames were identified as members of the two-component signal transduction systems in this single species of cyanobacteria.

To date, functional roles have been determined for only a limited number of such proteins. This review summarizes our current knowledge about the two-component signal transduction systems in Synechocystis sp.

PCC and describes recent achievements in elucidating the functional roles of these systems. Full Text Available Cells rely on accurate control of signaling systems to adapt to environmental perturbations. System deactivation upon stimulus removal is as important as activation of signaling pathways.

The two-component system TCS is one of the major bacterial signaling schemes. In many TCSs, phosphatase activity of the histidine kinase HK is believed to play an essential role in shutting off the pathway and resetting the system to the prestimulus state.

Two basic challenges are to understand the dynamic behavior of system deactivation and to quantitatively evaluate the role of phosphatase activity under natural cellular conditions. Here we report a kinetic analysis of the response to shutting off the archetype Escherichia coli PhoR-PhoB TCS pathway using both transcription reporter assays and in vivo phosphorylation analyses.

Upon removal of the stimulus, the pathway is shut off by rapid dephosphorylation of the PhoB response regulator RR while PhoB-regulated gene products gradually reset to prestimulus levels through growth dilution.

We developed an approach combining experimentation and modeling to assess in vivo kinetic parameters of the phosphatase activity with kinetic data from multiple phosphatase-diminished mutants.

This enabled an estimation of the PhoR phosphatase activity in vivo, which is much stronger than the phosphatase activity of PhoR cytoplasmic domains analyzed in vitro. We quantitatively modeled how strong the phosphatase activity needs to be to suppress nonspecific phosphorylation in TCSs and discovered that strong phosphatase activity of PhoR is required for cross-phosphorylation suppression.

Screening for compounds that affect the interaction between bacterial two-component signal transduction response regulator protein and cognate promoter DNA.

Bacterial signal transduction systems can be used as drug targets. The signal transduction targets fall into two groups--sensor kinases and response regulators. Previously reported studies describe hits that were thought to inactivate sensor kinases but on closer examination were found to act elsewhere instead; a possible reason for this is that full-length sensor kinases are integral membrane proteins whose activity might reflect interaction with the cell membrane or with membrane components.

We describe a model system that instead is based on the interaction between a test compound and a response regulator in a homogeneous phase reaction. In this system , response regulator-DNA complex formation and its inhibition by a test compound are measured by fluorescence polarization.

The model system should be readily adaptable to drug discovery based on other bacterial two-component s transduction systems. In this paper, firstly we study the series maintenance system with two components , obtain its exsistence and uniqueness of a dynamic state nonnegative solution by strongly continuous semigroups of operators theory.

Then we prove that 0 is the eigenvalue of the system 's host operators, and finally we study the eigenvector of the eigenvalue 0. Global dissipative solutions for the two-component Camassa-Holm shallow water system. Full Text Available This article presents a continuous semigroup of globally defined weak dissipative solutions for the two-component Camassa-Holm system. Such solutions are established by using a new approach based on characteristics a set of new variables overcoming the difficulties inherent in multi-component systems.

Two-component signal transduction pathways regulating growth and cell cycle progression in a bacterium: Full Text Available Two-component signal transduction systems , comprised of histidine kinases and their response regulator substrates, are the predominant means by which bacteria sense and respond to extracellular signals.

These systems allow cells to adapt to prevailing conditions by modifying cellular physiology, including initiating programs of gene expression, catalyzing reactions, or modifying protein-protein interactions. These signaling pathways have also been demonstrated to play a role in coordinating bacterial cell cycle progression and development.

Here we report a system -level investigation of two-component pathways in the model organism Caulobacter crescentus. First, by a comprehensive deletion analysis we show that at least 39 of the two-component genes are required for cell cycle progression, growth, or morphogenesis. These include nine genes essential for growth or viability of the organism. We then use a systematic biochemical approach, called phosphotransfer profiling, to map the connectivity of histidine kinases and response regulators.

Combining these genetic and biochemical approaches, we identify a new, highly conserved essential signaling pathway from the histidine kinase CenK to the response regulator CenR, which plays a critical role in controlling cell envelope biogenesis and structure. Depletion of either cenK or cenR leads to an unusual, severe blebbing of cell envelope material, whereas constitutive activation of the pathway compromises cell envelope integrity, resulting in cell lysis and death.

We propose that the CenK-CenR pathway may be a suitable target for new antibiotic development, given previous successes in targeting the bacterial cell wall. Finally, the ability of our in vitro phosphotransfer profiling method to identify signaling pathways that operate in vivo takes advantage of an observation that histidine kinases are endowed with a global kinetic preference for their cognate response regulators. We propose that this. A System -Level Analysis.

Two-component signal transduction systems , comprised of histidine kinases and their response regulator substrates, are the predominant means by which bacteria sense and respond to extracellular signals. These systems allow cells to adapt to prevailing conditions by modifying cellular physiology, including initiating programs of gene expression, catalyzing reactions, or modifying protein—protein interactions.

We propose that the CenK—CenR pathway may be a suitable target for new antibiotic development, given previous successes in targeting the bacterial cell wall. We propose that this system. Use of two-component signal transduction systems in the construction of synthetic genetic networks. Two-component signal transduction systems are a common type of signaling system in prokaryotes; the typical cell has dozens of systems regulating aspects of physiology and controlling responses to environmental conditions.

In this review, I consider how these systems may be useful for engineering novel cell functions. Examples of successful incorporation of two-component systems into engineered systems are noted, and features of the systems that favor or hinder potential future use of these signaling systems for synthetic biology applications are discussed.

The focus will be on the engineering of novel couplings of sensory functions to signaling outputs. Recent successes in this area are noted, such as the development of light-sensitive transmitter proteins and chemotactic receptors responsive to nitrate. A novel two-component system found in Mycobacterium tuberculosis. We report the identification of a novel two-component system in Mycobacterium tuberculosis. The essential YycFG two-component system controls cell wall metabolism in Bacillus subtilis.

Adaptation of bacteria to the prevailing environmental and nutritional conditions is often mediated by two-component signal transduction systems TCS. It is shown that the two-component Camassa-Holm and Hunter-Saxton systems are geometrically integrable, namely they describe pseudo-spherical surfaces.

As a consequence, their infinite number o, conservation laws are directly constructed. In addition, a class of nonlocal symmetries depending on the pseudo-potentials are obtained. Characterization of an archaeal two-component system that regulates methanogenesis in Methanosaeta harundinacea.

Full Text Available Two-component signal transduction systems TCSs are a major mechanism used by bacteria in response to environmental changes. Although many sequenced archaeal genomes encode TCSs, they remain poorly understood. Previously, we reported that a methanogenic archaeon, Methanosaeta harundinacea, encodes FilI, which synthesizes carboxyl-acyl homoserine lactones, to regulate transitions of cellular morphology and carbon metabolic fluxes. FilI possesses a cytoplasmic kinase domain histidine kinase A and histidine kinase-like ATPase and its cognate response regulator.

In a phosphorelay assay, FilI was autophosphorylated and specifically transferred the phosphoryl group to FilR1 and FilR2, confirming that the three formed a cognate TCS.

Through chromatin immunoprecipitation-quantitative polymerase chain reaction ChIP-qPCR using an anti-FilR1 antibody, FilR1 was shown to form in vivo associations with its own promoter and the promoter of the filI-filR2 operon, demonstrating a regulatory pattern common among TCSs.

Electrophoretic mobility shift assays confirmed the in vitro tight binding of FilR1 to its own promoter and those of filI-filR2, acs4, and mtrABC. The archaeal promoters of acs4, filI, acs1, and mtrABC also initiated FilR1-modulated expression in an Escherichia coli lux reporter system , suggesting that FilR1 can up-regulate both archaeal and bacterial transcription. The CpxRA two-component system is essential for Citrobacter rodentium virulence.

Citrobacter rodentium is a murine intestinal pathogen used as a model for the foodborne human pathogens enterohemorrhagic Escherichia coli and enteropathogenic E. During infection, these pathogens use two-component signal transduction systems to detect and adapt to changing environmental conditions. To determine whether CpxRA plays a role during C.

This defect was independent of an altered growth rate or a defective type III secretion system , and single-copy chromosomal complementation of cpxRA restored virulence. Furthermore, we found that the cpxRA expression level was higher during early infection than at a later time point. Taken together, these data demonstrate that the CpxRA two-component signal transduction system is essential for the in vivo virulence of C.

In addition, these data suggest that fine-tuned cpxRA expression is important for infection. This is the first study that identifies a C. This study further indicates that CpxRA is an interesting target for therapeutics against enteric pathogens. Bioinformatics analysis of two-component regulatory systems in Staphylococcus epidermidis.

Sixteen pairs of two-component regulatory systems are identified in the genome of Staphylococcus epidermidis ATCC strain, which is newly sequenced by our laboratory for Medical Molecular Virology and Chinese National Human Genome Center at Shanghai, by using bioinformatics analysis. Comparative analysis of the twocomponent regulatory systems in S.

Two conserved domains, i. Preliminary experiment reveals that the bioinformatics analysis of the conserved domain structures in the two-component regulatory systems in S.

Two-component signal transduction system SaeRS positively regulates Staphylococcus epidermidis glucose metabolism.

Staphylococcus epidermidis, which is a causative pathogen of nosocomial infection, expresses its virulent traits such as biofilm and autolysis regulated by two-component signal transduction system SaeRS. In this study, we performed a proteomic analysis of differences in expression between the S.

Of 55 identified proteins that significantly differed in expression between the two strains, 15 were upregulated and 40 were downregulated. The downregulated proteins included enzymes related to glycolysis and TCA cycle, suggesting that glucose is not properly utilized in S. The study will be helpful for treatment of S. Full Text Available Extra-intestinal pathogenic E. However, surprisingly little has been reported on the regulatory modules that have been identified as critical in ExPEC pathogenesis.

Two-component systems TCSs comprise the predominant method by which bacteria respond to changing environments and play significant roles in modulating bacterial fitness in diverse niches. Recent studies have highlighted the potential of manipulating signal transduction systems as a means to chemically re-wire bacterial pathogens, thereby reducing selective pressure and avoiding the emergence of antibiotic resistance.

This review begins by providing a brief introduction to characterized infection strategies and common virulence factors among APEC, NMEC, and UPEC and continues with a comprehensive overview of two-component signal transduction networks that have been shown to influence ExPEC pathogenesis. Full Text Available Using the multiple scales method, the interaction between two bright and one dark solitons is studied.

Provided that a long wave-short wave resonance condition is satisfied, the two-component Zakharov-Yajima-Oikawa ZYO completely integrable system is obtained.

By using a Madelung fluid description, the one-soliton solutions of the corresponding ZYO system are determined. Furthermore, a discussion on the interaction between one bright and two dark solitons is presented. In particular, this problem is reduced to solve a one-component ZYO system in the resonance conditions. Evolutionary analysis and lateral gene transfer of two-component regulatory systems associated with heavy-metal tolerance in bacteria.

Microorganisms have adapted intricate signal transduction mechanisms to coordinate tolerance to toxic levels of metals, including two-component regulatory systems TCRS.

In particular, both cop and czc operons are regulated by TCRS; the cop operon plays a key role in bacterial tolerance to copper, whereas the czc operon is involved in the efflux of cadmium, zinc, and cobalt from the cell.

Although the molecular physiology of heavy metal tolerance genes has been extensively studied, their evolutionary relationships are not well-understood. Phylogenetic relationships among heavy-metal efflux proteins and their corresponding two-component regulatory proteins revealed orthologous and paralogous relationships from species divergences and ancient gene duplications.

The presence of heavy metal tolerance genes on bacterial plasmids suggests these genes may be prone to spread through horizontal gene transfer. Phylogenetic inferences revealed nine potential examples of lateral gene transfer associated with metal efflux proteins and two examples for regulatory proteins. Notably, four of the examples suggest lateral transfer across major evolutionary domains.

In most cases, differences in GC content in metal tolerance genes and their corresponding host genomes confirmed lateral gene transfer events. Three-dimensional protein structures predicted for the response regulators encoded by cop and czc operons showed a high degree of structural similarity with other known proteins involved in TCRS signal transduction, which suggests common evolutionary origins of functional phenotypes and similar mechanisms of action for these response regulators.

Diversity of two-component systems: To understand the signal transduction mechanism by GraSR, we investigated the kinase activity of the cytoplasmic domain of histidine kinase GraS and the interaction with its cognate response regulator GraR. We found that GraS lacks autophosphorylation activity, unlike a similar histidine kinase, BceS, of Bacillus subtilis. We found that the auxiliary protein GraX interacts with VraF and GraR, and requires the histidine phosphotransfer and dimerization domain of GraS to interact with this protein.

Further, VraF requires the GraS region that connects the membrane-bound domain with the cytoplasmic domain of this protein for interaction with GraS. The Vibrio cholerae VprA-VprB two-component system controls virulence through endotoxin modification.

The bacterial cell surface is the first structure the host immune system targets to prevent infection.

Cationic antimicrobial peptides of the innate immune system bind to the membrane of Gram-negative pathogens via conserved, surface-exposed lipopolysaccharide LPS molecules. We recently reported that modern strains of the global intestinal pathogen Vibrio cholerae modify the anionic lipid A domain of LPS with a novel moiety, amino acids. Remarkably, glycine or diglycine addition to lipid A alters the surface charge of the bacteria to help evade the cationic antimicrobial peptide polymyxin. However, the regulatory mechanisms of lipid A modification in V.

Here, we identify a novel two-component system that regulates lipid A glycine modification by responding to important biological cues associated with pathogenesis, including bile, mildly acidic pH, and cationic antimicrobial peptides.

The histidine kinase Vc VprB and the response regulator Vc VprA respond to these signals and are required for the expression of the almEFG operon that encodes the genes essential for glycine modification of lipid A. Importantly, both the newly identified two-component system and the lipid A modification machinery are required for colonization of the mammalian host. This study demonstrates how V.

Vibrio cholerae, the etiological agent of cholera disease, infects millions of people every year. The El Tor biotype responsible for the current seventh pandemic has displaced the classical biotype worldwide and is highly resistant to cationic antimicrobial peptides, like polymyxin B. This resistance arises from the attachment of one or two glycine residues to the lipid A domain of. On the inspection policy of a two-component parallel system with failure interaction. In this paper we study a two-component standby system which can successfully operate upon a demand if at least one component is not failed.

We assume that failures can be detected only by periodic inspections. We consider that the failure of one component can modify the conditional failure probability of the component still alive with probability p and do not interact with probability 1-p.

For that failure interaction scheme we obtain the system reliability function for the case of staggered inspections. We compare staggered and non-staggered inspections through numerical examples considering constant hazard rates. Analysis of the activity and regulon of the two-component regulatory system encoded by Cjj and Cjj of Campylobacter jejuni.

Campylobacter jejuni is a leading cause of bacterial diarrheal disease throughout the world and a frequent commensal in the intestinal tract of poultry and many other animals. For maintaining optimal growth and ability to colonize various hosts, C. Dissecting the regulon of the two-component system CvsSR: Identifying new virulence genes in Pseudomonas syringae pv. Recognition of environmental changes and regulation of genes that allow for adaption to those changes is essential for survival of bacteria.

Two-component systems TCSs allow bacteria to sense and adapt to their environment. Identification of a second two-component signal transduction system that controls fosfomycin tolerance and glycerolphosphate uptake. Particular interest in fosfomycin has resurfaced because it is a highly beneficial antibiotic for the treatment of refractory infectious diseases caused by pathogens that are resistant to other commonly used antibiotics.

The biological cost to cells of resistance to fosfomycin because of chromosomal mutation is high. This mechanism does not rely on irreversible genetic modification and allows EHEC to relieve the fitness burden that results from fosfomycin resistance in the absence of fosfomycin.

Here we show that another two-component system , TorSRT, which was originally characterized as a regulatory system for anaerobic respiration utilizing trimethylamine-N-oxide TMAO , also induces fosfomycin tolerance.

We also show that phosphorylated TorR directly represses the expression of glpT, a gene that encodes a symporter of fosfomycin and glycerolphosphate, and activation of the TorR protein results in the reduced uptake of fosfomycin by cells. However, cells in which the Tor pathway was activated had an impaired growth phenotype when cultured with glycerolphosphate as a carbon substrate.

These observations suggest that the TorSRT pathway is the second two-component system to reversibly control fosfomycin tolerance and glycerolphosphate uptake in EHEC, and this may be beneficial for bacteria by alleviating the biological cost.

We expect that this mechanism could be a potential target to enhance the utility of fosfomycin as chemotherapy against multidrug-resistant pathogens.

Design principles in two component systems and his-asp phosphorelays. Two-component systems and their co-option for eukaryotic signal transduction. Two-component signaling pathways involve histidine kinases, response regulators, and sometimes histidine-containing phosphotransfer proteins.

Prevalent in prokaryotes, these signaling elements have also been co-opted to meet the needs of signal transduction in eukaryotes such as fungi and plants. Here we consider the evolution of such regulatory systems , with a particular emphasis on the roles they play in signaling by the plant hormones cytokinin and ethylene, in phytochrome-mediated perception of light, and as integral components of the circadian clock.

Motivated by present indirect evidence that galaxies are surrounded by dark matter halos, we investigate whether their physical properties can be described by a formulation of the virial theorem that explicitly takes into account the gravitational potential term representing the interaction of the dark halo with the baryonic or luminous component.

Our analysis shows that the application of such a " two-component virial theorem" not only accounts for the scaling relations displayed by, in particular, elliptical galaxies, but also for the observed properties of all virialized stellar systems , ranging from globular clusters to galaxy clusters. Two-component signal transduction systems , comprised of histidine kinases and their response regulator substrates, are the predominant means by which bacteria sense and respond to extracellular signals Full Text Available Calprotectin, the most abundant cytoplasmic protein in neutrophils, suppresses the growth of Staphylococcus aureus by sequestering the nutrient metal ions Zn and Mn.

Here we show that calprotectin can also enhance the activity of the SaeRS two component system TCS, a signaling system essential for production of over 20 virulence factors in S. The activity of the SaeRS TCS is repressed by certain divalent ions found in blood or neutrophil granules; however, the Zn bound-form of calprotectin relieves this repression. These results suggest that, under certain conditions, calprotectin can be exploited by S.

Calprotectin, the most abundant cytoplasmic protein in neutrophils, suppresses the growth of Staphylococcus aureus by sequestering the nutrient metal ions Zn and Mn. Here we show that calprotectin can also enhance the activity of the SaeRS two component system TCS , a signaling system essential for production of over 20 virulence factors in S.

Positive autoregulation shapes response timing and intensity in two-component signal transduction systems. Positive feedback loops are regulatory elements that can modulate expression output, kinetics and noise in genetic circuits. Transcriptional regulators participating in such loops are often expressed from two promoters, one constitutive and one autoregulated. Here, we investigate the interplay of promoter strengths and the intensity of the stimulus activating the transcriptional regulator in defining the output of a positively autoregulated genetic circuit.

Using a mathematical model of two-component regulatory systems , which are present in all domains of life, we establish that positive feedback strongly affects the steady-state output levels at both low and high levels of stimulus if the constitutive promoter of the regulator is weak. By contrast, the effect of positive feedback is negligible when the constitutive promoter is sufficiently strong, unless the stimulus intensity is very high.

Furthermore, we determine that positive feedback can affect both transient and steady state output levels even in the simplest genetic regulatory systems. Copyright c Elsevier Ltd. A two-component system regulates hemin acquisition in Porphyromonas gingivalis. Full Text Available Porphyromonas gingivalis is a Gram-negative oral anaerobe associated with infection of the periodontia.

The data showed that the regulon of this signal transduction system contained genes that were involved in hemin acquisition, including gingipains, at least three transport systems , as well as being self-regulated. Direct regulation by the response regulator was confirmed by electrophoretic mobility shift assays.

In addition, the system appears to be activated by hemin and the regulator acts as both an activator and repressor. Full Text Available Staphylococcus epidermidis, which is a causative pathogen of nosocomial infection, expresses its virulent traits such as biofilm and autolysis regulated by two-component signal transduction system SaeRS. Characterization of the Arc two-component signal transduction system of the capnophilic rumen bacterium Mannheimia succiniciproducens.

We demonstrate that the putative arcA and arcB genes of Mannheimia succiniciproducens MBEL55E, a capnophilic CO2-loving rumen bacterium, encode functional proteins that specify a two-component system. The Arc proteins of the two bacterial species sufficiently resemble each other that they can participate in heterologous transphosphorylation in vitro, and the arcA and arcB genes of M. However, neither the quinone analogs ubiquinone 0 and menadione nor the cytosolic effectors d-lactate, acetate, and pyruvate affect the net phosphorylation of M.

Our results indicate that different types of signaling molecules and distinct modes of kinase regulation are used by the ArcB proteins of E. Global solutions for the two-component Camassa-Holm system. We prove existence of a global conservative solution of the Cauchy problem for the two-component Camassa-Holm 2CH system on the line, allowing for nonvanishing and distinct asymptotics at plus and minus infinity.

The solution is proven to be smooth as long as the density is bounded away from zero. Furthermore, we show that by taking the limit of vanishing density in the 2CH system , we obtain the global conservative solution of the scalar Camassa-Holm equation, which provides a novel way to define and obtain these solutions. Finally, it is shown that while solutions of the 2CH system have infinite speed of propagation, singularities travel with finite speed.

Proteins exhibiting hyper-variable sequences within a bacterial pathogen may be associated with host adaptation. Several lineages of the monophyletic pathogen Salmonella enterica serovar Typhi S.

Typhi have accumulated non-synonymous mutations in the putative two-component regulatory system yehUT. Consequently we evaluated the function of yehUT in S. Typhi BRD and S. Transcriptome analysis identified the cstA gene, encoding a carbon starvation protein as the predominantly yehUT regulated gene in both these serovars.

Deletion of yehUT had no detectable effect on the ability of these mutant Salmonella to invade cultured epithelial cells S. Typhimurium or induce colitis in a murine model S. Growth, metabolic and antimicrobial susceptibility tests identified no obvious influences of yehUT on these phenotypes. In the Gram-positive pathogenic bacterium Staphylococcus aureus, the SaeRS two-component system TCS plays a major role in controlling the production of over 20 virulence factors including hemolysins, leukocidins, superantigens, surface proteins, and proteases.

Since its discovery in , the sae locus has been studied extensively, and its contributions to staphylococcal virulence and pathogenesis have been well documented and understood; however, the molecular mechanism by which the SaeRS TCS receives and processes cognate signals is not. In this article, therefore, we review the literature focusing on the signaling mechanism and its interaction with other global regulators. In this paper, we construct the addition formulae for several integrable hierarchies, including the discrete KP, the q-deformed KP, the two-component BKP and the D type Drinfeld-Sokolov hierarchies.

These studies show that the addition formula in the research of the integrable systems has good universality. Wong Magna Fund in Ningbo University. WalRK two component system of Bacillus anthracis responds to temperature and antibiotic stress. This report elaborates upon the WalRK genomic architecture, promoter structure, promoter activity and expression under various stress conditions in B. Reporter gene assays demonstrated maximal promoter activity during early growth phases indicating utility in exponential stages of growth.

Collectively, these results confirm that WalRK responds to cell envelope stress in B. Full Text Available Export of macromolecules via extracellular membrane-derived vesicles MVs plays an important role in the biology of Gram-negative bacteria. Gram-positive bacteria have also recently been reported to produce MVs; however, the composition and mechanisms governing vesiculogenesis in Gram-positive bacteria remain undefined. Here, we describe MV production in the Gram-positive human pathogen group A streptococcus GAS, the etiological agent of necrotizing fasciitis and streptococcal toxic shock syndrome.

M1 serotype GAS isolates in culture exhibit MV structures both on the cell wall surface and in the near vicinity of bacterial cells. Our data provide an explanation for GAS secretion of macromolecules, including RNAs, lipids, and proteins, and illustrate a regulatory mechanism coordinating this secretory response.

The cytosolic sensory kinase DegS does not receive a single predominant input signal like most two-component kinases, instead it integrates a wide array of metabolic inputs that modulate its activity Identification of a two-component signal transduction system that regulates maltose genes in Clostridium perfringens. Clostridium perfringens is a Gram-positive rod that is widely distributed in nature and is the etiological agent of several human and animal diseases.

The complete genome sequence of C. One of these systems , designated here as the MalNO system , was analyzed in this study. Microarray analysis was used to carry out functional analysis of a malO mutant.

The results, which were confirmed by quantitative reverse-transcriptase PCR, indicated that genes putatively involved in the uptake and metabolism of maltose were up-regulated in the malO mutant. These effects were reversed by complementation with the wild-type malO gene. Growth of these isogenic strains in medium with and without maltose showed that the malO mutant recovered more quickly from maltose deprivation when compared to the wild-type and complemented strains, leading to the conclusion that the MalNO system regulates maltose utilization in C.

It is postulated that this regulatory network may allow this soil bacterium and opportunistic pathogen to respond to environmental conditions where there are higher concentrations of maltose or maltodextrins, such as in the presence of decaying plant material in rich soil.

Two-component systems are involved in the regulation of botulinum neurotoxin synthesis in Clostridium botulinum type A strain Hall. Clostridium botulinum synthesizes a potent neurotoxin BoNT which associates with non-toxic proteins ANTPs to form complexes of various sizes.

The bont and antp genes are clustered in two operons. In the genome of C. Therefore, 34 Hall isogenic antisense strains on predicted regulatory genes 29 TCSs and 5 orphan regulatory genes have been obtained by a mRNA antisense procedure. Two-component system TCS signal transduction pathways are the dominant mechanisms by which micro-organisms sense and respond to external as well as internal environmental changes.

These systems respond to a wide range of stimuli by triggering diverse physiological adjustments, including alterations in gene expression, enzymatic reactions, or protein-protein interactions.

Description We present P2CS Prokaryotic 2-Component Systems , an integrated and comprehensive database of TCS signal transduction proteins, which contains a compilation of the TCS genes within completely sequenced prokaryotic genomes and 39 metagenomes.

P2CS provides detailed annotation of each TCS gene including family classification, sequence features, functional domains, as well as genomic context visualization. To bypass the generic problem of gene underestimation during genome annotation, we also constituted and searched an ORFeome, which improves the recovery of TCS proteins compared to searches on the equivalent proteomes. Conclusion P2CS has been developed for computational analysis of the modular TCSs of prokaryotic genomes and metagenomes.

The database can be browsed and queried with a user-friendly web interface at http: We present P2CS Prokaryotic 2-Component Systems , an integrated and comprehensive database of TCS signal transduction proteins, which contains a compilation of the TCS genes within completely sequenced prokaryotic genomes and 39 metagenomes.

P2CS has been developed for computational analysis of the modular TCSs of prokaryotic genomes and metagenomes. Two-component signal transduction systems TCSs , typically composed of a sensor histidine kinase HK and a response regulator RR , are the primary mechanism by which pathogenic bacteria sense and respond to extracellular signals.

The pathogenic bacterium Vibrio cholerae is no exception and harbors 52 RR genes. Using in-frame deletion mutants of each RR gene, we performed a systematic analysis of their role in V. We determined that 7 RRs impacted the expression of an essential biofilm gene and found that the recently characterized RR, VxrB, regulates the expression of key structural and regulatory biofilm genes in V. The overexpression of VxrB led to a decrease in motility. Our work reveals a new function for the Vxr TCS as a regulator of biofilm formation and suggests that this regulation may act through key biofilm regulators and the modulation of cellular c-di-GMP levels.

We performed a systematic analysis of V. We demonstrated that the VxrAB TCS is essential for robust biofilm formation and that this system may regulate biofilm formation via its regulation of key biofilm regulators and cyclic di-GMP levels. This research furthers our. A two component system is involved in acid adaptation of Lactobacillus delbrueckii subsp. The Gram-positive bacterium Lactobacillus delbrueckii subsp.

Two component systems TCSs are one of the most important mechanisms for environmental sensing and signal transduction in the majority of Gram-positive and Gram-negative bacteria. To investigate the functions of TCSs during acid adaptation in L. These TCSs were speculated to be related with the acid adaptation ability of L. The mutants showed reduced acid adaptation compared to that of wild type, and the complemented strains were similar to the wild-type strain.

The interaction between JN and JN was identified by means of yeast two-hybrid system. The results indicated there is interaction between JN and JN A hybrid two-component system protein from Azospirillum brasilense Sp7 was involved in chemotaxis. We here report the sequence and functional analysis of org35 of Azospirillum brasilense Sp7, which was originally identified to be able to interact with NifA in yeast-two-hybrid system.

To determine the function of the Org35, a deletion-insertion mutant in PAS domain [named Sp] and a complemental strain SpC were constructed. The mutant had reduced chemotaxis ability compared to that of wild-type, and the complemental strain was similar to the wild-type strain. These data suggested that the A. Variants containing different domains of the org35 were expressed, and the functions of these domains were studied in vitro. Phosphorylation assays in vitro demonstrated that the HPK domain of Org35 possessed the autokinase activity and that the phosphorylated HPK was able to transfer phosphate groups to the RR domain.

The result indicated Org35 was a phosphorylation-communicating protein. Photoisomerization-induced morphology and transparency transition in an azobenzene based two-component organogel system. A two-component gel containing long chain alkylated gallic acid GA and photochromic phenazopyridine PAP was prepared. The structure and transparency of the two-component gel can be reversibly changed by alternative UV light irradiation and warming in the palm of the hand.

This kind of soft material has potential application in upscale surface functional materials. It was shown previously that its dysfunction alters the expression of some major outer membrane proteins and the pattern of lipid A acylation. A total of differentially expressed genes were found: Two operons, the phosphotransferase system and the maltose transport system , were down-regulated.

Several genes involved in cell envelope or outer membrane biogenesis were differentially expressed: Ten genes related with carbon metabolism pckA and fumB among others were up-regulated in the bvrR mutant, and denitrification genes nirK, norC and nosZ were also regulated. Finally, the expression of eleven genes which have been previously related with Brucella virulence was also altered.

Full Text Available The LiaSR two-component signal transduction system regulates cellular responses to several environmental stresses, including those that induce cell envelope damages. Downstream regulons of the LiaSR system have been implicated in tolerance to acid, antibiotics and detergents.

In the dental pathogen Streptococcus mutans, the LiaSR system is necessary for tolerance against acid, antibiotics, and cell wall damaging stresses during growth in the oral cavity.

To understand the molecular mechanisms by which LiaSR regulates gene expression, we created a mutant LiaR in which the conserved aspartic acid residue the phosphorylation site, was changed to alanine residue D58A. As expected, the LiaR-D58A variant was unable to acquire the phosphate group and bind to target promoters.

We also noted that the predicted LiaR-binding motif upstream of the lia operon does not appear to be well conserved. Consistent with this observation, we found that LiaR was unable to bind to the promoter region of lia; however, we showed that LiaR was able to bind to the promoters of SMU. Based on sequence analysis and DNA binding studies we proposed a new bp conserved motif essential for LiaR binding.

Introducing alterations at fully conserved positions in the bp motif affected LiaR binding, and the binding was dependent on the combination of positions that were altered. By scanning the S. Taken together our results suggest a putative role of the LiaSR system in heat shock responses of S. Analysis of protein expression regulated by the Helicobacter pylori ArsRS two-component signal transduction system.

Previous studies have shown that the Helicobacter pylori ArsRS two-component signal transduction system contributes to acid-responsive gene expression. To identify additional members of the ArsRS regulon and further investigate the regulatory role of the ArsRS system , we analyzed protein expression in wild-type and arsS null mutant strains.

Numerous proteins were differentially expressed in an arsS mutant strain compared to a wild-type strain when the bacteria were cultured at pH 5. Genes encoding 14 of these proteins were directly regulated by the ArsRS system , based on observed binding of ArsR to the relevant promoter regions. The ArsRS-regulated proteins identified in this study contribute to acid resistance urease and amidase , acetone metabolism acetone carboxylase , resistance to oxidative stress thioredoxin reductase , quorum sensing Pfs , and several other functions.

These results provide further definition of the ArsRS regulon and underscore the importance of the ArsRS system in regulating expression of H. Regulation of acid resistance by connectors of two-component signal transduction systems in Escherichia coli. Two-component signal transduction systems TCSs , utilized extensively by bacteria and archaea, are involved in the rapid adaptation of the organisms to fluctuating environments.

A typical TCS transduces the signal by a phosphorelay between the sensor histidine kinase and its cognate response regulator. Recently, small-sized proteins that link TCSs have been reported and are called "connectors. Species of the genus Streptomyces are major bacteria responsible for producing most natural antibiotics. Streptomyces coelicolor A3 2 and Streptomyces avermitilis were sequenced in and ,respectively.

Two-component signal transduction systems TCSs , consisting of a histidine sensor kinase SK and a cognate response regulator RR , form the most common mechanism of transmembrane signal transduction in prokaryotes. Phylogenetic analysis of the cognate SK-RR pairs of the two species indicated that the cognate SK-RR pairs fall into four classes according to the distribution of their orthologs in other organisms.

Our study provides new clues for further exploration of the molecular regulation mechanism of streptomycetes with industrial importance. TCSs generally consist of sensor histidine kinases that autophosphorylate in response to a specific stimulus and subsequently transfer the phosphate group to their cognate response regulators thus modulating their activity, usually as transcriptional regulators.

In this review we present the current knowledge on the physiological role of TCSs in species of the families Lactobacillaceae and Leuconostocaceae of the group of lactic acid bacteria LAB. LAB are microorganisms of great relevance for health and food production as the group spans from starter organisms to pathogens.

However, evidence available indicates that TCSs are key players in the regulation of the physiology of these bacteria. Functional characterization of WalRK: A two-component signal transduction system from Bacillus anthracis. Full Text Available Two-component signal transduction systems TCS, consisting of a sensor histidine protein kinase and its cognate response regulator, are an important mode of environmental sensing in bacteria.

Additionally, they have been found to regulate virulence determinants in several pathogens. Bacillus anthracis, the causative agent of anthrax and a bioterrorism agent, harbours 41 pairs of TCS. However, their role in its pathogenicity has remained largely unexplored.

Here, we show that WalRK of B. Biochemical studies showed that domain variants of WalK, the histidine kinase, exhibit classical properties of autophosphorylation and phosphotransfer to its cognate response regulator WalR. An in silico regulon determination approach, using a consensus binding sequence from Bacillus subtilis, provided a list of 30 genes that could form a putative WalR regulon in B. Further, electrophoretic mobility shift assay was used to show direct binding of purified WalR to the upstream regions of three putative regulon candidates, an S-layer protein EA1, a cell division ABC transporter FtsE and a sporulation histidine kinase KinB3.

Our work lends insight into the species-specific functions and mode of action of B. Two-component signal transduction systems TCS , consisting of a sensor histidine protein kinase and its cognate response regulator, are an important mode of environmental sensing in bacteria. Lactobacillus casei has traditionally been recognized as a probiotic, thus needing to survive the industrial production processes and transit through the gastrointestinal tract before providing benefit to human health.

The two-component signal transduction system TCS plays important roles in sensing and reacting to environmental changes, which consists of a histidine kinase HK and a response regulator RR. Further classification of the predicted HKs and RRs revealed interesting aspects of their putative functions. Some TCS clusters are involved with the response under the stress of the bile salts, acid, or oxidative, which contribute to survive the difficult journey through the human gastrointestinal tract.

Identification of the regulatory logic controlling Salmonella pathoadaptation by the SsrA-SsrB two-component system. Full Text Available Sequence data from the past decade has laid bare the significance of horizontal gene transfer in creating genetic diversity in the bacterial world. Regulatory evolution, in which non-coding DNA is mutated to create new regulatory nodes, also contributes to this diversity to allow niche adaptation and the evolution of pathogenesis.

To survive in the host environment, Salmonella enterica uses a type III secretion system and effector proteins, which are activated by the SsrA-SsrB two-component system in response to the host environment. To better understand the phenomenon of regulatory evolution in S.

Using ChIP-on-chip, cDNA hybridization, and comparative genomics analyses, we describe the SsrB-dependent regulon of ancestral and horizontally acquired genes. Further, we used a genetic screen and computational analyses integrating experimental data from S. Mutational analysis of a representative promoter validated this palindrome as the minimal architecture needed for regulatory input by SsrB.

These data provide a high-resolution map of a regulatory network and the underlying logic enabling pathogen adaptation to a host.

Inhibitors targeting two-component signal transduction. A two-component signal transduction system TCS is an attractive target for antibacterial agents. Conformational transition of response regulator RR in a two-component system signal transduction process. Signal transduction can be accomplished via a two-component system TCS consisting of a histidine kinase HK and a response regulator RR.

Unexpectedly, the microorganism also contains candidate genes, organized in operon-like structures that potentially encode at least 11 siderophore systems for the uptake of Fe III , although it does not exhibit genes that could encode the biosynthesis of the siderophores themselves. Jedlicki Program of Cellular and Molecular Biology, Faculty of Medicine, University of Chile, Santiago, Chile aerobic environments where iron is scarce and where siderophore producers are present.

It may also help to explain why it cannot tolerate high Fe III concentrations in bioleaching operations where it is out-competed by Leptospirillum species. One of the most studied microorganisms involved in bioleaching is Acidithiobacillus ferrooxidans, formerly called Thiobacillus ferrooxidans [33]. It thrives in extremely acidic conditions pH 1—2 and is often confronted with high concentrations of metals including iron.

These multiple challenges make it an excellent choice for understanding microbial physiology in extreme environments. Knowledge of its metabolism is also essential for describing its role in the bioleaching process and in the biogeochemical recycling of iron, sulfur, carbon and nitrogen in extreme acid environments.

Knowledge of its role in the development and maintenance of its associated consortium is important for generating a comprehensive description of its role in mineral leaching and environmentally associated processes. Recently, a nearly complete genome sequence of the type strain A. One aspect of the physiology of A. Iron is an essential micronutrient for all organisms, where it plays a central role in redox reactions. Although iron is the most abundant transition metal on Earth, its solubility is very low at neutral pH in aerobic environments.

In such environments, Fe II is generally not available because it rapidly oxidizes to Fe III , which precipitates as insoluble ferric ion complexes. Given its limited bioavailability, most microorganisms have been faced with the need to develop specialized uptake mechanisms to scavenge iron from their environment [5]. On the other hand, excess intracellular Fe II acts as a catalyst in Haber-Weiss-Fenton chemistry, which leads to the production of reactive oxygen species Fig.

The hydroxyl radical HO is considered to be the most toxic, damaging lipids, proteins and nucleic acids. A number of enzymes and cofactors function in microorganisms to detoxify oxygen radicals. However, a key method to reduce radical formation is to limit the intracellular availability of iron. By sensing iron levels, limiting its uptake, and sequestering excess iron in storage proteins, organisms have developed tight intracellular homeostatic controls to balance Fig. The hydroxyl radical HO is considered to be the most toxic to biological processes.

This poses several interesting questions: Storage of iron may be less important for A. In this report we develop preliminary models of iron uptake, regulation and storage of iron in A.

We describe the characteristics of these Fe III uptake systems. Interestingly, the feoAB gene cluster in A. PorA exhibits similarity to OprB, which belongs to a family of porins COG, pfam implicated in the movement of carbohydrates across the outer membrane [55, 67] that can also transport other ions [68], suggesting that PorA may participate in the uptake of Fe II. The prediction of a Fur box-like sequence upstream of the putative A.

Recently, a hypothetical gene encoding a porin of the OprB family, which is immediately followed by a FeoAB-type transporter and preceded by a predicted Fur box, was also described in Geobacter sulfurreducens [52]. Fe III uptake Most organisms living in neutrophilic and oxic conditions have evolved a variety of iron uptake systems to Fig. Some groups of bacteria, most notably those that are pathogenic to animals, can obtain iron directly from host iron-binding proteins such as transferrin and lactoferrin [16], or indirectly through heme from hemoglobin by utilizing hemophores [22].

However, most bacteria take up iron via ferri-siderophores [34, 65]. They are synthesized and excreted into the environment by many bacteria and fungi. Producers of siderophores usually have cognate receptors for the siderophores. However, many microorganisms have receptors for siderophores that they do not synthesize, allowing them to compete for iron with siderophore producers. However, it does have 11 candidate genes for several potential siderophore outer membrane receptors OMRs Fig.

This immediately suggests that it can live in environments in which Fe III availability is limiting and in which other organisms capable of producing siderophores are present. TonB is an energy transduction protein anchored in the inner membrane of Gram-negative bacteria, and spans the periplasm contacting the siderophore receptor embedded in the outer membrane.

Iron storage Once the Fe III reaches the cytoplasm it is reduced to Fe II and subsequently incorporated into proteins and hemes or is stored for future supply into iron-storage proteins like bacterioferritin and ferritins Fig. Iron sensing and regulation A crucial aspect for the preservation of iron homeostasis is sensitive iron-responsive regulation [17, 26].

Fe III -dependent PmrAB regulation, has been hypothesized to be essential for Salmonella survival in extracellular envi- ronments [11] and necessary for the survival of Erwinia carotovora on excess iron at acidic pH [30]. Three candidate genes belonging to the Fur family of metallo-responsive regulators are also present in A.

It has been demonstrated to function in E. The frequency of potential OMRs exhibited by A. An analysis of the Nitrosomonas europaea [9] genome revealed more than 20 candidate siderophore OMRs, about 32 putative siderophore OMRs were also found in P.

The diversity of OMRs exhibited by A. There are several possible explanations for this observation. It may be that they represent non-active pseudogenes that are not required for iron uptake. However, their amino acid sequence conservation, including the conservation of functional motifs, and their organization in operon-like gene clusters argues against this interpretation.

Future experimental investigation will be required to examine this option. At the latter pH in aerobic environments iron begins to become limiting, favoring the selection of active iron uptake systems. The presence of siderophore OMRs but the apparent absence of siderophore biosynthesis systems in A.

Interestingly, the 11 distinct siderophore OMRs of A. Whereas neutrophilic bacteria like E. Supporting this view is the fact that the acid tolerant Helicobacter pylori has four receptors for ferric-dicitrate all with pIs above 8.

The range of pIs exhibited by A. In these circumstances Leptospirillum strains appear to dominate the microbial population, an observation that has been attributed to their ability to grow in the presence of high concentrations of Fe III , which selects against A.

How might interactions between Fe III uptake proteins be maintained in an acidic environment? Outer membrane and periplasmic proteins, and periplasmic loops of proteins embedded in the inner membrane of A. Can genome analysis of the pertinent proteins in A. We have noted amino acid changes in the predicted channel facing portions of the b-barrel of A. Sequence and structural similarities of the A.

Iron transport across the outer membrane is an energydependent process that relies on the electrochemical potential PMF, proton motif force of the inner membrane and the energy transduction complex TonBExbB-ExbD [4]. In the acidic growth environment of A. TonB appears to shuttle between the cytoplasmic and outer membranes, extracting the ligand from the OMRs and passing it to a cytoplasmic metal binding protein.

There are six putative candidate TonB-class proteins predicted in the A. Given that this central domain appears to be important for the ability of TonB to bridge the periplasmic space by allowing TonB to adopt a rigid extended conformation [36], these substitutions could represent a functional adaptation of the TonB of A.

Heteromultimers of ExbB and ExbD are thought to constitute a proton-translocating unit. Both proteins are anchored in the inner membrane and predicted inner membrane embedded loops of the putative ExbB and ExbD of A. There are also crystal structures at 1.

All ABC-transporter components, including those with domains in the periplasm, are highly conserved with respect to neutrophilic counterparts. General primary sequence conservation of these components further supports that a predicted mechanism of siderophore uptake similar to those found in other organisms accumulating Fe III in iron-poor conditions may exist in A.

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Linear and branched bicin linkers for releasable PEGylation of macromolecules: Linear and non-linear pressure dependence of enzyme catalytic parameters. Linear and nonlinear QSAR study of N-hydroxy[ phenylsulfonyl amino]acetamide derivatives as matrix metalloproteinase inhibitors. Linear and nonlinear causality between signals: Linear and nonlinear fetal heart rate analysis of normal and acidemic fetuses in the minutes preceding delivery.

Linear and nonlinear functions on modeling of aqueous solubility of organic compounds by two structure representation methods. Linear and nonlinear measures and seizure anticipation in temporal lobe epilepsy. Linear and nonlinear relationships between neuronal activity, oxygen metabolism, and hemodynamic responses. Linear artificial molecular muscles.

Linear basal cell carcinoma: Linear basic peptides for targeting interferon-gamma-glycosaminoglycan interactions: Linear blood velocity in arteries of the brain hemispheres in left-handers and right-handers during hypoxia. Linear combination filtering for T2-selective imaging of the knee. Linear combination of multiecho data: Linear consociation equation set model of forest ecological benefits.

Linear correlation between fractal dimension of EEG signal and handgrip force. Linear correlation in experimental design models applied to seed germination. Linear cryoablation of the left atrium versus pulmonary vein cryoisolation in patients with permanent atrial fibrillation and valvular heart disease - Correlation of electroanatomic mapping and long-term clinical results. Linear decrease in VO2max and performance with increasing altitude in endurance athletes.

Montanari, Angela , Linear discriminant analysis and transvariation. Linear discriminant analysis of dermoscopic parameters for the differentiation of early melanomas from Clark naevi.

Linear double-stranded DNA that mimics an infective tail of virus genome to enhance transfection. Linear enamel hypoplasias as indicators of systemic physiological stress: Linear encoding of muscle activity in primary motor cortex and cerebellum. Linear energy transfer dependence of a normoxic polymer gel dosimeter investigated using proton beam absorbed dose measurements. Linear energy transfer dependence of the effects of carbon ion beams on adventitious shoot regeneration from in vitro leaf explants of Saintpaulia ionahta.

Linear equations with random variables. Linear estimate of red-and-white animal exterior. Linear free energy relationship as a tool for characterization of three teicoplanin-based chiral stationary phases under various mobile phase compositions.

Linear free energy relationship for 4-substituted o-phenylenediamine platinum II dichloride derivatives using quantum mechanical descriptors. Linear free-energy analysis of mercury II and cadmium II binding to three-stranded coiled coils.

Linear furanocoumarin protects rat myocardium against lipidperoxidation and membrane damage during experimental myocardial injury. Linear fuzzy gene network models obtained from microarray data by exhaustive search.

Ghiaus, Cristian , Linear fuzzy-discriminant analysis applied to forecast ozone concentration classes in sea-breeze regime. Linear growth after enterocystoplasty in children and adolescents: Linear high intensity area along the medial margin of the internal segment of the globus pallidus in Machado-Joseph disease patients.

The floral and butterfly diversity of green lanes. Linear independence of pairwise comparisons of DNA microarray data. Linear interaction energy models for beta-secretase BACE inhibitors: Role of van der Waals, electrostatic, and continuum-solvation terms. Linear interpolation error in measured surfaces in a dental erosion study. Linear joint calcifications while treating osteoporosis: Linear life expectancy regression with censored data.

Linear mixed-effects models for weight-length relationships. Linear modelling analysis of baroreflex control of arterial pressure variability in rats. Linear models for microarray data analysis: Linear molecules of tobacco ptDNA end at known replication origins and additional loci. Linear nevus comedonicus with epidermolytic hyperkeratosis.

Linear ordering and dynamic segregation of the bacterial chromosome. Linear parameter haplotype models with stratification. Linear patterns of Alzheimer's disease mutations along alpha-helices of presenilins as a tool for PS-1 model construction. Linear pharmacokinetics of micafungin and its active metabolites in Japanese pediatric patients with fungal infections.

Linear polyamines as carriers in thiocyanate-selective membrane electrodes. Linear polyethyleneimine grafted to a hyperbranched poly ethylene glycol -like core: Linear polyp measurement at CT colonography: Linear quadratic modeling of increased late normal-tissue effects in special clinical situations.

Linear recursive distributed representations. Linear regression analysis and its application to multivariate chromatographic calibration for the quantitative analysis of two-component mixtures. Linear regression analysis and its application to the multivariate spectral calibrations for the multiresolution of a ternary mixture of caffeine, paracetamol and metamizol in tablets. Linear regression and two-class classification with gene expression data. Linear regression based QSPR models for the prediction of the retention mechanism of some nitrogen containing heterocycles.

Linear regression models for solvent accessibility prediction in proteins. Linear relationship between Wnt activity levels and apoptosis in colorectal carcinoma cells exposed to butyrate. Linear relationship between the perception of effort and the duration of constant load exercise that remains.

Linear relationship of valproate serum concentration to response and optimal serum levels for acute mania. Linear scan voltammetric indirect determination of Al III by the catalytic cathodic response of norepinephrine at the hanging mercury drop electrode. Linear scleroderma 'en coup de sabre' associated with cerebral and ocular vasculitis.

Linear scleroderma en coup de sabre with associated neurologic abnormalities. Linear social dominance hierarchy and corticosterone responses in male mallards and pintails. Linear stability and first order normalization inplanar restricted three body problem when more massive and infinitesimal bodies are oblate spheroid. Linear summation of Cat Motor Cortex Ouputs vol 26, pg , Linear summation of cat motor cortex outputs.

Linear sweep voltammetric determination of heparin based on its interaction with neutral red. Linear sweep voltammetric studies on the interaction of brilliant cresyl blue with nucleic acids and its analytical application.

Linear systems approach to analysis of complex dynamic behaviours in biochemical networks. Linear temporal characteristics of heart interbeat interval as an index of the pilot's perceived risk.

Linear thinning in a clonal test of eucalyptus Camaldulensis for conversion to a clonal seed orchard. Linear three-iron centres are unlikely cluster degradation intermediates during unfolding of iron-sulfur proteins. Linear topology confers in vivo gene transfer activity to polyethylenimines.

Linear transformations of the payoff matrix and decision criterion learning in perceptual categorization. Linear type azo-containing polyurethanes for colon-specific drug delivery.

Linear versus nonlinear QSAR modeling of the toxicity of phenol derivatives to Tetrahymena pyriformis. Linear width of the medial temporal lobe can discriminate Alzheimer's disease from normal aging: Linear-Nonlinear-Poisson models of primate choice dynamic.

Linear-dichroic infrared spectral analysis of Cu I -homocysteine complex. Linear-no-threshold is a radiation-protection standard rather than a mechanistic effect model. Linearity and time-scale invariance of the creep function in living cells. Linearity assumption in soil-to-plant transfer factors of natural uranium and radium in Helianthus annuus L. Linearity evaluation of analytical methods that count particles. Linearity of cortical receptive fields measured with natural sounds.

Linearized kinetic model of Listeria monocytogenes biofilm growth. Lineaue determination of CDB-cell neoplasms: Linee guida per una banca dati delle aree sensibili: Lines of arrested growth in bone and age estimation in a small primate: Linezolid and human polymorphonuclear leukocyte function. Linezolid as rescue drug: Linezolid compared with teicoplanin for the treatment of suspected or proven Gram-positive infections.

Linezolid contributed to Clostridium difficile colitis with fatal outcome. Linezolid does not increase the risk of thrombocytopenia in patients with nosocomial pneumonia: Linezolid for the treatment of a heteroresistant Staphylococcus aureus shunt infection.

Linezolid for the treatment of children with bacteremia or nosocomial pneumonia caused by resistant gram-positive bacterial pathogens.

Linezolid for the treatment of complicated skin and skin structure infections in children. Linezolid for the treatment of methicillin-resistant Staphylococcus aureus infections in children. Linezolid for the treatment of multidrug-resistant tuberculosis. Linezolid for the treatment of patients with endocarditis: Linezolid in prophylaxis against experimental aortic valve endocarditis due to Streptococcus oralis or Enterococcus faecalis.

Linezolid in the treatment of Gram-positive prosthetic joint infections. Linezolid in the treatment of brain abscess due to Peptostreptococcus. Linezolid in the treatment of osteomyelitis: Linezolid penetration into bone and joint tissues infected with methicillin-resistant staphylococci.

Linezolid pharmacokinetics in pediatric patients: Linezolid reduces length of stay and duration of intravenous treatment compared with vancomycin for complicated skin and soft tissue infections due to suspected or proven methicillin-resistant Staphylococcus aureus MRSA. Linezolid therapy for orthopedic infections. Linezolid treatment of glycopeptide-resistant Enterococcus faecium in very low birth weight premature neonates.

Linezolid use associated with lactic acidosis. Linezolid versus teicoplanin in the treatment of Gram-positive infections in the critically ill: Linezolid versus vancomycin for Staphylococcus aureus bacteraemia: Linezolid versus vancomycin in the treatment of known or suspected resistant gram-positive infections in neonates.

Linezolid versus vancomycin in treatment of complicated skin and soft tissue infections. Linezolid, levofloxacin, and vancomycin against vancomycin-tolerant and fluoroquinolone-resistant Streptococcus pneumoniae in an in vitro pharmacodynamic model.

Linezolid-associated toxic optic neuropathy. Linezolid-associated toxic optic neuropathy: Linezolid-induced inhibition of mitochondrial protein synthesis. Linezolid-resistant Staphylococcus aureus in two pediatric patients receiving low-dose linezolid therapy. Analisis de su utilizacion.

Linezolide, donnees recentes experimentales in vitro et in vivo. Linfadenectomia en el cancer gastrico: Linfadenectomia retroperitoneal via laparoscopica postquimioterapia. Linfangioma quistico retroperitoneal gigante en adulto. Linfoadenitis necrotizante por Nocardia asteroides en una nina previamente sauna.

Linfoma B rico en celulas T. Linfoma de Hodgkin con afectacion osea: Linfoma de celulas en anillo de sello que simula carcinoma mucosecretante. Linfoma espontaneo de celulas-B em hamster. Linfoma linfocitico, bien diferenciado de la prostata, presentacion de un caso y breve revision de la literatura. Linfoma osseo em cao. King, Jr; Haggarty, Dr , Lingering effects of disfluent material on comprehension of garden path sentences.

Lingering mysteries of ubiquitin-chain assembly. Lingshuiol, a novel polyhydroxyl compound with strongly cytotoxic activity from the marine dinoflagellate Amphidinium sp. Lingshuiols A and B, two new polyhydroxy compounds from the Chinese marine dinoflagellate Amphidinium sp.

Lingual alveolar soft part sarcoma; 14 cases: Lingual artery bifurcation aneurysms for training and evaluation of neurovascular devices. Lingual cyst lined by squamous epithelium. Lingual deficits in neurotrophin double knockout mice.

Lingual harmatoma in an infant. Lingual incisor traits in modern hominoids and an assessment of their utility for fossil hominoid taxonomy.

Lingual metastasis from renal cell carcinoma management and review of the literature. Lingual nerve injury associated with the ProSeal laryngeal mask airway: Lingual striated muscle hamartoma or herniation? Lingual subgemmal neurogenous plaques with pseudoepitheliomatous hyperplasia: Lingual tactile acuity, taste perception, and the density and diameter of fungiform papillae in female subjects. Lingual, splanchnic, and systemic hemodynamic and carbon dioxide tension changes during endotoxic shock and resuscitation.

Krapp-Schickel, Traudl , Linguimaera Pirlot, Crustacea, Amphipoda, Melitidae , a valid genus. Linguistic analysis of college aged smokers and never smokers. Linguistic and nonlinguistic influences on the eyes' landing positions during reading. Linguistic determinants of word colouring in grapheme-colour synaesthesia. Linguistic disparities in health care access and health status among older adults. Linguistic focus and good-enough representations: An application of the change-detection paradigm.

Linguistic prominence and Broca's area: Linguistic stress, within-word position, and grammatical class in relation to early childhood stuttering. Lorenzo-Gonzalez, Guillermo , Hacia un enfoque modular e internista. Linguistically mediated visual search: Mergl, Michal , Linguliformean and craniiformean brachiopods of the Ordovician Trenice to Dobrotiva Formations of the Barrandian, Bohemia.

Gonzalez-Gomez, Cristina , Linitis plastica primaria de colon: Link between biological signaling and increased enantioseparations of acids using glycopeptide antibiotics. Link between environmental anomalies, growth and condition of pilchard Sardina pilchardus larvae in the northwestern Mediterranean. Link between free radicals and protein kinase C in glucose-induced alteration of vascular dilation.

Link between macrophage migration inhibitory factor and cellular redox regulation. Link between monoamine oxidase and nitric oxide.

Link between primary and secondary metabolism in the biotransformation of trimethylammonium compounds by escherichia coli. Link between reduced nephron number and hypertension: Linkage analyses of chromosomal region 18pq12 in dyslexia. Linkage analyses of event-related potential slow wave phenotypes recorded in a working memory task. Linkage analyses of four regions previously implicated in dyslexia: Linkage analysis and association analysis in the presence of linkage using age at onset of COGA alcoholism data.

Linkage analysis and disease models in benign familial infantile seizures: Linkage analysis and molecular haplotyping of the dopamine D4 receptor gene promoter region. Linkage analysis for autism in a subset families with obsessive-compulsive behaviors: Linkage analysis in a large Swedish family supports the presence of a susceptibility locus for adenoma and colorectal cancer on chromosome 9q Linkage analysis in bipolar pedigrees adds support for a susceptibility locus on 21q Linkage analysis localises a Kartagener syndrome gene to a 3.

Linkage analysis of a completely ascertained sample of familial schizophrenics and bipolars from Palau, Micronesia. Linkage analysis of a derived glucose phenotype in the Genetic Analysis Workshop 13 simulated data using a variety of Haseman-Elston based regression methods. Linkage analysis of adult height with parent-of-origin effects in the Framingham Heart Study.

Linkage analysis of affected sib pairs allowing for parent-of-origin effects. Linkage analysis of alcohol dependence using MOD scores. Linkage analysis of alcohol dependence using both affected and discordant sib pairs. Linkage analysis of alcoholism-related electrophysiological phenotypes: Linkage analysis of anorexia and bulimia nervosa cohorts using selected behavioral phenotypes as quantitative traits or covariates.

Linkage analysis of chromosome 1 with essential hypertension and blood pressure quantitative traits in Chinese families. Linkage analysis of chromosome 14 and essential hypertension in Chinese population.

Linkage analysis of chromosome 1q markers in prostate cancer families vol 62, pg , Linkage analysis of complex diseases using microsatellites and single-nucleotide polymorphisms: Linkage analysis of cross-sectional and longitudinally derived phenotypic measures to identify loci influencing blood pressure.

Linkage analysis of diabetes status among hypertensive families: Linkage analysis of extremely discordant and concordant sibling pairs identifies quantitative trait loci influencing variation in human menopausal age. Linkage analysis of five Chinese families with arrhythmogenic right ventricular cardiomyopathy using microsatellite genetic markers. Linkage analysis of longitudinal data. Linkage analysis of longitudinal data and design consideration.

Linkage analysis of neointimal hyperplasia and vascular wall transformation after balloon angioplasty. Linkage analysis of ordinal traits for pedigree data. Linkage analysis of plasma ApoE in three ethnic groups: Linkage analysis of polymorphisms near the lipoprotein lipase gene with hypertension or blood pressure in Chinese.

Linkage analysis of several microsatellite genetic markers with arrhythmogenic right ventricular cardiomyopathy in 5 Chinese families.

Linkage analysis of systolic blood pressure: Linkage analysis of the GAW14 simulated dataset with microsatellite and single-nucleotide polymorphism markers in large pedigrees. Linkage analysis of the genetic loci for high myopia on 18p, 12q, and 17q in 51 U. Linkage analysis of the simulated data - evaluations and comparisons of methods.

Linkage analysis of two families with X-linked recessive congenital motor nystagmus. Linkage analysis using co-phenotypes in the BRIGHT study reveals novel potential susceptibility loci for hypertension.

Linkage analysis using single nucleotide polymorphisms. Linkage analysis with an interbreed backcross maps Dalmatian hyperuricosuria to CFA Linkage analysis with gene-environment interaction: Linkage and association analyses of microsatellites and single-nucleotide polymorphisms in nuclear families. Linkage and association analyses of the UCP3 gene with obesity phenotypes in Caucasian families. Linkage and association analysis in pedigrees from different populations.

Linkage and association between CA repeat polymorphism of the TNFR2 gene and obesity phenotypes in two independent Caucasian populations. Linkage and association mapping of a chromosome 1qq24 type 2 diabetes susceptibility locus in northern European Caucasians. Linkage and association of childhood asthma with the chromosome 12 genes. Linkage and association of febrile seizures to the IMPA2 gene on human chromosome Linkage and association of the CA repeat polymorphism of the IL6 gene, obesity-related phenotypes, and bone mineral density BMD in two independent Caucasian populations.

Linkage and association studies identify a novel locus for Alzheimer disease at 7q36 in a Dutch population-based sample. Linkage and association studies of discoidin domain receptor 1 DDR1 single nucleotide polymorphisms SNPs in juvenile oligoarthritis. Linkage and association studies of the susceptibility genes for type 2 diabetes.

Linkage and association with the NOS2A locus on chromosome 17q11 in multiple sclerosis. Linkage and candidate gene analysis of 14q in bipolar disorder: Linkage and linkage disequilibrium analysis of the lipoprotein lipase gene with lipid in Chinese hypertensive families. Linkage and mutational analysis of familial thyroid dysgenesis demonstrate genetic heterogeneity implicating novel genes. Linkage between Werner syndrome protein and the Mre11 complex via Nbs1.

Linkage between androgen receptor gene CAG trinucleotide repeat length and testicular germ cell cancer histological type and clinical stage. Linkage between catecholate siderophores and the multicopper oxidase CueO in Escherichia coli.

Linkage between cellular communications, energy utilization, and proliferation in metastatic neuroendocrine cancers. Linkage between cryptorchidism, hypospadias, and GGN repeat length in the androgen receptor gene.

Linkage between mechanical and electrical alternans in patients with chronic heart failure. Linkage between proton binding and folding in RNA: Linkage between riparian buffer features and regeneration, benthic communities, and water temperature in headwater streams, Western Oregon. Linkage between stress and fruit and vegetable intake among university students: Linkage between the proteasome pathway and neurodegenerative diseases and aging.

Linkage disequilibrium across two different single-nucleotide polymorphism genome scans. Linkage disequilibrium analysis of case-control data: Linkage disequilibrium analysis of polymorphisms in the gene for myelin oligodendrocyte glycoprotein in Tourette's syndrome patients from a Chinese sample. Linkage disequilibrium analysis of the dopamine beta-hydroxylase gene in persistent attention deficit hyperactivity disorder.

Linkage disequilibrium and haplotype analysis of two single nucleotide polymorphisms in STK15 in Chinese. Linkage disequilibrium and haplotype tagging polymorphisms in the Tau H1 haplotype.

Linkage disequilibrium and heritability of copy-number polymorphisms within duplicated regions of the human genome. Linkage disequilibrium and recent selection at three immunity receptor loci in Drosophila simulans. Linkage disequilibrium as a signature of selective sweeps. Linkage disequilibrium assessment via log-linear modeling of SNP haplotype frequencies.

Linkage disequilibrium between microsatellite markers in the Swedish Sami relative to a worldwide selection of populations. Linkage disequilibrium fine mapping and haplotype association analysis of the tau gene in progressive supranuclear palsy and corticobasal degeneration.

Linkage disequilibrium for different scales and applications. Linkage disequilibrium grouping of single nucleotide polymorphisms SNPs reflecting haplotype phylogeny for efficient selection of tag SNPs. Linkage disequilibrium in cultivated grapevine, Vitis vinifera L.

Linkage disequilibrium inflates type I error rates in multipoint linkage analysis when parental genotypes are missing. Linkage disequilibrium interval mapping of quantitative trait loci.

Linkage disequilibrium mapping in domestic dog breeds narrows the progressive rod-cone degeneration interval and identifies ancestral disease-transmitting chromosome. Linkage disequilibrium mapping of CHEK2: Linkage disequilibrium mapping of bipolar affective disorder at 12qq24 provides evidence for association at CUX2 and FLJ Linkage disequilibrium mapping of quantitative-trait Loci by selective genotyping.

Linkage disequilibrium mapping via cladistic analysis of phase-unknown genotypes and inferred haplotypes in the Genetic Analysis Workshop 14 simulated data. Linkage disequilibrium maps and association mapping. Linkage disequilibrium maps constructed with common SNPs are useful for first-pass disease association screens. Linkage disequilibrium of the brain-derived neurotrophic factor Val66Met polymorphism in children with a prepubertal and early adolescent bipolar disorder phenotype.

Linkage disequilibrium on chromosome 6 in Australian Holstein-Friesian cattle. Linkage disequilibrium on the bovine X chromosome: Linkage disequilibrium patterns and tagSNP transferability among European populations. Linkage disequilibrium sharing and haplotype-tagged SNP portability between populations. Linkage disequlibrium in the DTNBP1 dysbindin gene region and on chromosome 1p36 among psychotic patients from a genetic isolate in Israel: Linkage evidence of schizophrenia to loci near neuregulin 1 gene on chromosome 8p21 in Taiwanese families.

Linkage exclusion analysis of two important chromosomal regions for height. Linkage exclusion mapping with bone size in 79 Caucasian pedigrees. Linkage identity is a major factor in determining the effect of PEG-ylated surfactants on permeability of phosphatidylcholine liposomes.

Linkage map construction and mapping of a dominant genic male sterility gene Ms in Brassica napus. Linkage mapping and physical localization of the major histocompatibility complex region of the marsupial Monodelphis domestica. Linkage mapping methods applied to the COGA data set: Linkage mapping of new maize candidate gene Loci.

Linkage mapping of canine rod cone dysplasia type 2 rcd2 to CFA7, the canine orthologue of human 1q Linkage mapping of powdery mildew and greenbug resistance genes on recombinant IRS from 'Amigol and 'Kavkaz' wheat-rye translocations of chromosome 1RS. Linkage mapping of total cholesterol level in a young cohort via nonparametric regression. Linkage mapping reveals sex-dimorphic map distances in a passerine bird.

Linkage methods in human genetics before the computer. Linkage of Ii-Key segment to gp epitope enhances the production of epitope-specific antibodies.

Linkage of M5 muscarinic and alpha7-nicotinic receptor genes on 15q13 to schizophrenia. Linkage of a novel mercury resistance operon with streptomycin resistance on a conjugative plasmid in Enterococcus faecium. Linkage of amino acid variation and evolution of human immunodeficiency virus type 1 gp envelope glycoprotein subtype B with usage of the second receptor. Linkage of avian and reproductive tract tropism with sequence divergence adjacent to the 5S ribosomal subunit rrfH of Salmonella enterica.

Linkage of biomarkers along levels of biological complexity in juvenile and adult diazinon fed terrestrial isopod Porcellio scaber, Isopoda, Crustacea. Linkage of butterfly mate preference and wing color preference cue at the genomic location of wingless. Linkage of calpain 10 to type 2 diabetes: Linkage of ciprofloxacin resistance with a single genotypic cluster of Klebsiella pneumoniae. Linkage of conservation activity to trends in the U.

Linkage of erm B and aadE-sat4-aphA-3 in multiple-resistant Enterococcus faecium isolates of different ecological origins. Linkage of eye movement dysfunction to chromosome 6p in schizophrenia: Linkage of familial hemophagocytic lymphohistiocytosis FHL type-4 to chromosome 6q24 and identification of mutations in syntaxin Linkage of genes controlling morphological traits with isozyme markers of rye chromosomes.

Linkage of genes responsible for sex determination and expression of a sperm-specific isozyme of glucosephosphate isomerase in the polychaete Polydora brevipalpa.

Linkage of genetics and ethics: Linkage of interactions in sickle hemoglobin fiber assembly: Linkage of late-onset Fuchs corneal dystrophy to a novel locus at 13pTelq Linkage of microbiology reports and hospital discharge diagnoses for surveillance of surgical site infections. Linkage of monogenic infantile hypertrophic pyloric stenosis to chromosome 16pp13 and evidence for genetic heterogeneity. Linkage of myostatin pathway genes with knee strength in humans. Linkage of neutrophil serine proteases and decreased surfactant protein-A SP-A levels in inflammatory lung disease.

Linkage of osteoporosis to chromosome 20p12 and association to BMP2. Linkage of plasma adiponectin levels to 3q27 explained by association with variation in the APM1 gene. Linkage of proton binding to the thermal dissociation of triple helix complex.

Linkage of reduced receptor affinity and superinfection to pathogenesis of TR1. Linkage of serum creatinine and glomerular filtration rate to chromosome 2 in Utah pedigrees. Linkage of speech sound disorder to reading disability loci. Linkage of the beta-like omega-globin gene to alpha-like globin genes in an Australian marsupial supports the chromosome duplication model for separation of globin gene clusters.

Linkage of the metabolic syndrome to 1qq31 in Hispanic families: Linkage of ulcerative colitis to the pericentromeric region of chromosome 16 in Italian inflammatory bowel disease families is independent of the presence of common CARD15 mutations. Linkage study of the glucagon receptor gene with type 2 diabetes mellitus in Italians. Linkage to 10q22 for maximum intraocular pressure and 1p32 for maximum cup-to-disc ratio in an extended primary open-angle glaucoma pedigree.

Linkage to apnea-hypopnea index across the life-span: Linkage to chromosome 14q in Alzheimer's-disease AD patients without psychotic symptoms. Linkage to nodal osteoarthritis: Linkage to the FOXC2 region of chromosome 16 for varicose veins in otherwise healthy, unselected sibling pairs.

Linkage with methadone treatment upon release from incarceration: Linkages among land-use, water quality, physical habitat conditions and lotic diatom assemblages: A multi-spatial scale assessment. Linkages between biodiversity loss and human health: Jha, Shree Gopal , Linkages between biological and cultural diversity for participatory management: Full Text Available The bacterial flagellum is a locomotive organelle that propels the bacterial cell body in liquid environments.

The flagellum is a supramolecular complex composed of about 30 different proteins and consists of at least three parts: The flagellar motor of Escherichia coli and Salmonella enterica is powered by an inward-directed electrochemical potential difference of protons across the cytoplasmic membrane. FliG, FliM and FliN also act as a molecular switch, enabling the motor to spin in both counterclockwise and clockwise directions.

Each stator is anchored to the peptidoglycan layer through the C-terminal periplasmic domain of MotB and acts as a proton channel to couple the proton flow through the channel with torque generation. Highly conserved charged residues at the rotor—stator interface are required not only for torque generation but also for stator assembly around the rotor.

In this review, we will summarize our current understanding of the structure and function of the proton-driven bacterial flagellar motor. Complete structure of the bacterial flagellar hook reveals extensive set of stabilizing interactions. The bacterial flagellar hook is a tubular helical structure made by the polymerization of multiple copies of a protein, FlgE. Here we report the structure of the hook from Campylobacter jejuni by cryo-electron microscopy at a resolution of 3.

On the basis of this structure, we show that the hook is stabilized by intricate inter-molecular interactions between FlgE molecules. Extra domains in FlgE, found only in Campylobacter and in related bacteria, bring more stability and robustness to the hook.

Functional experiments suggest that Campylobacter requires an unusually strong hook to swim without its flagella being torn off. This structure reveals details of the quaternary organization of the hook that consists of 11 protofilaments. Previous study of the flagellar filament of Campylobacter by electron microscopy showed its quaternary structure made of seven protofilaments.

Therefore, this study puts in evidence the difference between the quaternary structures of a bacterial filament and its hook.

Autonomously responsive pumping by a bacterial flagellar forest: This study is motivated by a microfluidic device that imparts a magnetic torque on an array of bacterial flagella. Bacterial flagella can transform their helical geometry autonomously in response to properties of the background fluid, which provides an intriguing mechanism allowing their use as an engineered element for the regulation or transport of chemicals in microscale applications.

The synchronization of flagellar phase has been widely studied in biological contexts, but here we examine the synchronization of flagellar tilt, which is necessary for effective pumping. We first examine the effects of helical geometry and tilt on the pumping flows generated by a single rotating flagellum.

Next, we explore a mean-field model for an array of helical flagella to understand how collective tilt arises and influences pumping. The mean-field methodology allows us to take into account possible phase differences through a time-averaging procedure and to model an infinite array of flagella. We find array separation distances, magnetic field strengths, and rotation frequencies that produce nontrivial self-consistent pumping solutions. For individual flagella, pumping is reversed when helicity or rotation is reversed; in contrast, when collective effects are included, self-consistent tilted pumping solutions become untilted nonpumping solutions when helicity or rotation is reversed.

The bacterial flagellar type III export apparatus utilizes ATP and proton motive force PMF to transport flagellar proteins to the distal end of the growing flagellar structure for self-assembly. Here, we report that the export gate complex can use sodium motive force SMF in addition to PMF across the cytoplasmic membrane to drive protein export. Coordinated switching of bacterial flagellar motors: The swimming of Escherichia coli is powered by its multiple flagellar motors.

There can be two mechanisms extrinsic and intrinsic to coordinate the switching of bacterial motors. The extrinsic one arises from the fact that different motors in the same cell sense a common input CheY-P which fluctuates near the motors' response threshold.

An alternative, intrinsic mechanism is direct motor-motor coupling which makes synchronized switching energetically favorable. Here, we develop simple models for both mechanisms and uncover their different hallmarks. A quantitative comparison to the recent experiments suggest that the direct coupling mechanism may be accountable for the observed sharp correlation between motors in a single E.

Possible origins of this coupling e. Assembly and stoichiometry of the core structure of the bacterial flagellar type III export gate complex. The bacterial flagellar type III export apparatus, which is required for flagellar assembly beyond the cell membranes, consists of a transmembrane export gate complex and a cytoplasmic ATPase complex.

However, it remains unknown how they form the gate complex. Here we report that FliP forms a homohexameric ring with a diameter of 10 nm. FliO formed a 5-nm ring structure with 3 clamp-like structures that bind to the FliP6 ring. Nonequivalence of membrane voltage and ion-gradient as driving forces for the bacterial flagellar motor at low load.

Many bacterial species swim using flagella. The flagellar motor couples ion flow across the cytoplasmic membrane to rotation. Ion flow is driven by both a membrane potential V m and a transmembrane concentration gradient. To investigate their relation to bacterial flagellar motor function we developed a fluorescence technique to measure V m in single cells, using the dye tetramethyl rhodamine methyl ester.

We also estimated the sodium-motive force SMF by combining single-cell measurements of V m and intracellular sodium concentration. Rotation rates for 0. For the larger beads, the two components of the SMF were equivalent, whereas for smaller beads at a given SMF, the speed increased with sodium gradient and external sodium concentration.

Non-equilibrium effect in the allosteric regulation of the bacterial flagellar switch. The switching mechanism of the flagellar motor provides the basis for the motile behaviour of flagellated bacteria. Its highly sensitive response has previously been understood in terms of equilibrium models, either the classical two-state concerted allosteric model, or more generally, the Ising-type conformation spread model.

Here, we systematically study motor switching under various load conditions from high to zero load, under different proton motive force pmf conditions and varying the number of torque-generating units stators. In doing so, we reveal the signature of a non-equilibrium effect. To consistently account for the motor-switching dependence on each those conditions, a previously neglected non-equilibrium effect--the energy input from the motor torque--has to be incorporated into models of the flagellar switch.

We further show that this effect increases the sensitivity of the flagellar switch. Exploiting a very small fraction of the energy expense of the flagellar motor for functional regulation increases its sensitivity greatly. Similar mechanisms are expected to be found in other protein complexes. FliZ is a global regulatory protein affecting the expression of flagellar and virulence genes in individual Xenorhabdus nematophila bacterial cells.

Full Text Available Heterogeneity in the expression of various bacterial genes has been shown to result in the presence of individuals with different phenotypes within clonal bacterial populations. The genes specifying motility and flagellar functions are coordinately regulated and form a complex regulon, the flagellar regulon.

Complex interplay has recently been demonstrated in the regulation of flagellar and virulence gene expression in many bacterial pathogens. We show here that FliZ, a DNA-binding protein, plays a key role in the insect pathogen, Xenorhabdus nematophila, affecting not only hemolysin production and virulence in insects, but efficient swimming motility. RNA-Seq analysis identified FliZ as a global regulatory protein controlling the expression of Xenorhabdus genes either directly or indirectly.

FliZ is required for the efficient expression of all flagellar genes, probably through its positive feedback loop, which controls expression of the flhDC operon, the master regulator of the flagellar circuit. FliZ also up- or downregulates the expression of numerous genes encoding non- flagellar proteins potentially involved in key steps of the Xenorhabdus lifecycle. Single-cell analysis revealed the bimodal expression of six identified markers of the FliZ regulon during exponential growth of the bacterial population.

In addition, a combination of fluorescence-activated cell sorting and RT-qPCR quantification showed that this bimodality generated a mixed population of cells either expressing "ON state" or not expressing "OFF state" FliZ-dependent genes.

Moreover, studies of a bacterial population exposed to a graded series of FliZ concentrations showed that FliZ functioned as a rheostat, controlling the rate of transition between the "OFF" and "ON" states in individuals.

FliZ thus plays a key role in cell fate decisions, by transiently creating individuals with different potentials for motility and host interactions. We present a minimal physical model for the flagellar motor that enables bacteria to swim. Our model explains the experimentally measured torque-speed relationship of the proton-driven E.

Moreover, we show that shot noise in the proton current dominates the diffusion of motor rotation at low loads.

This suggests a new way to probe the discreteness of the energy source, analogous to measurements of charge quantization in superconducting tunnel junctions. Modeling torque versus speed, shot noise, and rotational diffusion of the bacterial flagellar motor. In particular, the dramatic drop of torque at high rotation speeds the "knee" is shown to arise from saturation of the proton flux.

The membrane protein FlhB is a highly conserved component of the flagellar secretion system, and it plays an active role in the regulation of protein export. In this study conserved properties of FlhB that are important for its function were investigated. Replacing the flhB gene or part of the gene in Salmonella typhimurium with the flhB gene of the distantly related bacterium Aquifex aeolicus greatly reduces motility.

However, motility can be restored to some extent by spontaneous mutations in the part of flhB gene coding for the cytoplasmic domain of Aquifex FlhB. Structural analysis suggests that these mutations destabilize the structure. The secondary structure and stability of the mutated cytoplasmic fragments of FlhB have been studied by circular dichroism spectroscopy. The results suggest that conformational flexibility could be important for FlhB function.

An extragenic suppressor mutation in the fliS gene, which decreases the affinity of FliS to FliC, partially restores motility of the FlhB substitution mutants. Function of FlhB, a membrane protein implicated in the bacterial flagellar type III secretion system. Full Text Available The membrane protein FlhB is a highly conserved component of the flagellar secretion system, and it plays an active role in the regulation of protein export. The non- flagellar type III secretion system evolved from the bacterial flagellum and diversified into host-cell adapted systems.

Yet the origin, specialization, and diversification of these machineries remained unclear. We developed computational tools to identify homologous components of the two systems and to discriminate between them. Phylogenomic and comparative analyses of these systems argue that the NF-T3SS arose from an exaptation of the flagellum, i. This reconstructed chronology of the exaptation process proceeded in at least two steps.

We argue that this ancestral version was involved in protein translocation. In rhizobiales, a partial homologous gene replacement of the secretin resulted in two genes of complementary function. Acquisition of a secretin was followed by the rapid adaptation of the resulting NF-T3SSs to multiple, distinct eukaryotic cell envelopes where they became key in parasitic and mutualistic associations between prokaryotes and eukaryotes. It demonstrates how molecular evolution can convert one complex molecular machine into a second, equally complex machine by successive deletions, innovations, and recruitment from other molecular systems.

Dickeya dadantii is a globally dispersed phytopathogen which causes diseases on a wide range of host plants. This pathogen utilizes the type III secretion system T3SS to suppress host defense responses, and secretes pectate lyase Pel to degrade the plant cell wall. Although the regulatory small RNA sRNA RsmB, cyclic diguanylate monophosphate c-di-GMP and flagellar regulator have been reported to affect the regulation of these two virulence factors or multiple cell behaviours such as motility and biofilm formation, the linkage between these regulatory components that coordinate the cell behaviours remain unclear.

A microhydrodynamic rationale for selection of bead size in preparation of drug nanosuspensions via wet stirred media milling. Although wet stirred media milling has proven to be a robust process for producing nanoparticle suspensions of poorly water-soluble drugs and thereby enhancing their bioavailability, selection of bead size has been largely empirical, lacking fundamental rationale. This study aims to establish such rationale by investigating the impact of bead size at various stirrer speeds on the drug breakage kinetics via a microhydrodynamic model.

To this end, stable suspensions of griseofulvin, a model BCS Class II drug, were prepared using hydroxypropyl cellulose and sodium dodecyl sulfate. Our results suggest that there is an optimal bead size that achieves fastest breakage at each stirrer speed and that it shifts to a smaller size at higher speed. Calculated microhydrodynamic parameters reveal two counteracting effects of bead size: The optimal bead size exhibits a negative power-law correlation with either specific energy consumption or the microhydrodynamic parameters.

Overall, this study rationalizes the use of smaller beads for more energetic wet media milling. Many-body microhydrodynamics of colloidal particles with active boundary layers. Colloidal particles with active boundary layers—regions surrounding the particles where non-equilibrium processes produce large velocity gradients—are common in many physical, chemical and biological contexts. The velocity or stress at the edge of the boundary layer determines the exterior fluid flow and, hence, the many-body interparticle hydrodynamic interaction.

Here, we present a method to compute the many-body hydrodynamic interaction between N spherical active particles induced by their exterior microhydrodynamic flow. First, we use a boundary integral representation of the Stokes equation to eliminate bulk fluid degrees of freedom. Then, we expand the boundary velocities and tractions of the integral representation in an infinite-dimensional basis of tensorial spherical harmonics and, on enforcing boundary conditions in a weak sense on the surface of each particle, obtain a system of linear algebraic equations for the unknown expansion coefficients.

The truncation of the infinite series, fixed by the degree of accuracy required, yields a finite linear system that can be solved accurately and efficiently by iterative methods. The solution linearly relates the unknown rigid body motion to the known values of the expansion coefficients, motivating the introduction of propulsion matrices. These matrices completely characterize hydrodynamic interactions in active suspensions just as mobility matrices completely characterize hydrodynamic interactions in passive suspensions.

The reduction in the dimensionality of the problem, from a three-dimensional partial differential equation to a two-dimensional integral equation, allows for dynamic simulations of hundreds of thousands of active particles on multi-core computational architectures. Specificity of motor components in the dual flagellar system of Shewanella putrefaciens CN Bacterial flagellar motors are intricate nanomachines in which the stator units and rotor component FliM may be dynamically exchanged during function.

Similar to other bacterial species, the gammaproteobacterium Shewanella putrefaciens CN possesses a complete secondary flagellar system along with a corresponding stator unit. Expression of the secondary system occurs during planktonic growth in complex media and leads to the formation of a subpopulation with one or more additional flagella at random positions in addition to the primary polar system.

We used physiological and phenotypic characterizations of defined mutants in concert with fluorescent microscopy on labelled components of the two different systems, the stator proteins PomB and MotB, the rotor components FliM 1 and FliM 2 , and the auxiliary motor components MotX and MotY, to determine localization, function and dynamics of the proteins in the flagellar motors.

The components were highly specific for their corresponding motor and are unlikely to be extensively swapped or shared between the two flagellar systems under planktonic conditions. The results have implications for both specificity and dynamics of flagellar motor components. Recent studies demonstrated that post-translational modifications PTMs such as phosphorylation, methylation, glutamylation, and ubiquitination are involved in these processes.

Accurate translation of the genetic information from DNA to protein is maintained by multiple quality control steps from bacteria to mammals. Genetic and environmental alterations have been shown to compromise translational quality control and reduce fidelity during protein synthesis. The physiological impact of increased translational errors is not fully understood.

While generally considered harmful, translational errors have recently been shown to benefit cells under certain stress conditions. In this work, we describe a novel regulatory pathway in which reduced translational fidelity downregulates expression of flagellar genes and suppresses bacterial motility. Electron microscopy imaging shows that the error-prone Escherichia coli strain lacks mature flagella. Further genetic analyses reveal that translational errors upregulate expression of a small RNA DsrA through enhancing its transcription, and deleting DsrA from the error-prone strain restores motility.

We demonstrate that an increased level of DsrA in the error-prone strain suppresses motility through the H-NS pathway.

Our work suggests that bacteria are capable of switching on and off the flagellar system by altering translational fidelity, which may serve as a previously unknown mechanism to improve fitness in response to environmental cues.

Flagellar membrane proteins in kinetoplastid parasites. All kinetoplastid parasites, including protozoa such as Leishmania species, Trypanosoma brucei, and Trypanosoma cruzi that cause devastating diseases in humans and animals, are flagellated throughout their life cycles.

Although flagella were originally thought of primarily as motility organelles, flagellar functions in other critical processes, especially in sensing and signal transduction, have become more fully appreciated in the recent past. The flagellar membrane is a highly specialized subdomain of the surface membrane, and flagellar membrane proteins are likely to be critical components for all the biologically important roles of flagella.

In this review, we summarize recent discoveries relevant to flagellar membrane proteins in these parasites, including the identification of such proteins, investigation of their biological functions, and mechanisms of selective trafficking to the flagellar membrane. Prospects for future investigations and current unsolved problems are highlighted.

Swimming performance of Bradyrhizobium diazoefficiens is an emergent property of its two flagellar systems. Many bacterial species use flagella for self-propulsion in aqueous media. In the soil, which is a complex and structured environment, water is found in microscopic channels where viscosity and water potential depend on the composition of the soil solution and the degree of soil water saturation.

Therefore, the motility of soil bacteria might have special requirements. An important soil bacterial genus is Bradyrhizobium, with species that possess one flagellar system and others with two different flagellar systems. Among the latter is B. These two flagellar systems were observed here as functionally integrated in a swimming performance that emerged as an epistatic interaction between those appendages.

In addition, each flagellum seemed engaged in a particular task that might be required for swimming oriented toward chemoattractants near the soil inner surfaces at viscosities that may occur after the loss of soil gravitational water. Because the possession of two flagellar systems is not general in Bradyrhizobium or in related genera that coexist in the same environment, there may be an adaptive tradeoff between energetic costs and ecological benefits among these different species.

A protein thermometer controls temperature-dependent transcription of flagellar motility genes in Listeria monocytogenes. Full Text Available Facultative bacterial pathogens must adapt to multiple stimuli to persist in the environment or establish infection within a host.

Temperature is often utilized as a signal to control expression of virulence genes necessary for infection or genes required for persistence in the environment. However, very little is known about the molecular mechanisms that allow bacteria to adapt and respond to temperature fluctuations. Listeria monocytogenes Lm is a food-borne, facultative intracellular pathogen that uses flagellar motility to survive in the extracellular environment and to enhance initial invasion of host cells during infection.

In this study, we determined that GmaR is also a protein thermometer that controls temperature-dependent transcription of flagellar motility genes. Two-hybrid and gel mobility shift analyses indicated that the interaction between MogR and GmaR is temperature sensitive. Using circular dichroism and limited proteolysis, we determined that GmaR undergoes a temperature-dependent conformational change as temperature is elevated.

GmaR complex is less stable. Since MogR represses transcription of all flagellar motility genes, including transcription of gmaR, changes in the stability of the MogR: GmaR anti-repression complex, due to conformational changes in GmaR, mediates repression or de-repression of flagellar motility genes in Lm. Thus, GmaR functions as. Load Response of the Flagellar Beat. Cilia and flagella exhibit regular bending waves that perform mechanical work on the surrounding fluid, to propel cellular swimmers and pump fluids inside organisms.

Here, we quantify a force-velocity relationship of the beating flagellum, by exposing flagellated Chlamydomonas cells to controlled microfluidic flows.

A simple theory of flagellar limit-cycle oscillations, calibrated by measurements in the absence of flow, reproduces this relationship quantitatively. We derive a link between the energy efficiency of the flagellar beat and its ability to synchronize to oscillatory flows. Identification of Archaea-specific chemotaxis proteins which interact with the flagellar apparatus.

Full Text Available Abstract Background Archaea share with bacteria the ability to bias their movement towards more favorable locations, a process known as taxis. Two molecular systems drive this process: The first consists of the flagellum, the flagellar motor, and its switch, which allows cells to reverse the rotation of flagella. The second targets the flagellar motor switch in order to modulate the switching frequency in response to external stimuli.

While the signal transduction system is conserved throughout archaea and bacteria, the archaeal flagellar apparatus is different from the bacterial one. The proteins constituting the flagellar motor and its switch in archaea have not yet been identified, and the connection between the bacterial -like chemotaxis signal transduction system and the archaeal motility apparatus is unknown.

In-frame deletion strains for all three proteins were generated and analyzed as follows: In these mutants, flagella rotate only clockwise, resulting in exclusively forward swimming cells that are unable to respond to tactic signals. Deletion of the second DUF protein had only minimal effects.

Seroprevalence in chickens against campylobacter jejuni flagellar capping protein FliD in selected areas of the U. Campylobacter jejuni, a Gram-negative rod, is a zoonotic pathogen associated with human acute bacterial gastroenteritis.

Poultry products are regarded as a major source for human infection with this microorganism. We have demonstrated that the flagellar capping protein FliD of C. The stator consists of several units located in the cytoplasmic membrane surrounding the flagellar drive shaft. Studies on flagellar motors of several bacterial species have provided evidence that the number as well as the retention time of stators coupled to the motor is highly dynamic and depends on the environmental conditions.

Notably, numerous species possess more than a single distinct set of stators. It is likely that the presence of different stator units enables these bacteria to adjust the flagellar motor properties and function to meet the environmental requirements.

Here, we describe a method to determine stator dynamics by fluorescence microscopy, demonstrating how bacteria can change the composition of an intricate molecular machine according to environmental conditions.

Full Text Available Molecular motors, which are precision-engineered by nature, offer exciting possibilities for bio-hybrid engineered systems. This review describes the fundamental biological insights and fascinating potentials of these remarkable sensing and actuation machines, in particular bacterial flagellar motors, as well as their engineering perspectives with regard to applications in bio-engineered hybrid systems and nanobiotechnology.

Microhydrodynamics and complex fluids. It will be useful to technicians, medical scientists and pharmaceutical chemists as a source of detailed information on advanced flow processes.

The articles are of a high scientific standard and include interesting examples from many different areas of rheology. The flagellar -specific transcription factor, sigma28, is the Type III secretion chaperone for the flagellar -specific anti-sigma28 factor FlgM. The sigma 28 protein is a member of the bacterial sigma 70 -family of transcription factors that directs RNA polymerase to flagellar late class 3 promoters. The sigma 28 protein is regulated in response to flagellar assembly by the anti-sigma 28 factor FlgM.

FlgM inhibits sigma 28 -dependent transcription of genes whose products are needed late in assembly until the flagellar basal motor structure, the hook-basal body HBB , is constructed. A second function for the sigma 28 transcription factor has been discovered: Transcription-specific mutants in sigma 28 were isolated that remained competent for FlgM-facilitated secretion separating the transcription and secretion-facilitation activities of sigma Conversely, we also describe the isolation of mutants in sigma 28 that are specific for FlgM-facilitated secretion.

Thus, a novel role for a sigma 70 -family transcription factor is described. Flagellar Motility of Trypanosoma cruzi Epimastigotes. Full Text Available The hemoflagellate Trypanosoma cruzi is the causative agent of American trypanosomiasis. Despite the importance of motility in the parasite life cycle, little is known about T. Using video microscopy and quantitative vectorial analysis of epimastigote trajectories, we find a forward parasite motility defined by tip-to-base symmetrical flagellar beats.

This motion is occasionally interrupted by base-to-tip highly asymmetric beats, which represent the ciliary beat of trypanosomatid flagella. The switch between flagellar and ciliary beating facilitates the parasite's reorientation, which produces a large variability of movement and trajectories that results in different distance ranges traveled by the cells. An analysis of the distance, speed, and rotational angle indicates that epimastigote movement is not completely random, and the phenomenon is highly dependent on the parasite behavior and is characterized by directed and tumbling parasite motion as well as their combination, resulting in the alternation of rectilinear and intricate motility paths.

Full Text Available Most bacteria that swim are propelled by flagellar filaments, which are driven by a rotary motor powered by proton flux. The mechanism of the flagellar motor is discussed by reforming the model proposed by the present authors in It is shown that the mean strength of Coulomb field produced by a proton passing the channel is very strong in the Mot assembly so that the Mot assembly can be a shear force generator and induce the flagellar rotation.

The model gives clear calculation results in agreement with experimental observations, e g. An unusual promoter controls cell-cycle regulation and dependence on DNA replication of the Caulobacter fliLM early flagellar operon. Transcription of flagellar genes in Caulobacter crecentus is programmed to occur during the predivisional stage of the cell cycle. The mechanism of activation of Class II flagellar genes, the highest identified genes in the Caulobacter flagellar hierarchy, is unknown. As a step toward understanding this process, we have defined cis-acting sequences necessary for expression of a Class II flagellar operon, fliLM.

Deletion analysis indicated that a 55 bp DNA fragment was sufficient for normal, temporally regulated promoter activity. Transcription from this promoter-containing fragment was severely reduced when chromosomal DNA replication was inhibited. Extensive mutational analysis of the promoter region from to -5 identified functionally important nucleotides at and , between and , and at , which correlates well with sequences conserved between fliLM and the analogous regions of two other Class II flagellar operons.

The promoter sequence does not resemble that recognized by any known bacterial sigma factor. Models for regulation of Caulobacter early flagellar promoters are discussed in which RNA polymerase containing a novel sigma subunit interacts with an activation factor bound to the central region of the promoter.

A role for the membrane in regulating Chlamydomonas flagellar length. Full Text Available Flagellar assembly requires coordination between the assembly of axonemal proteins and the assembly of the flagellar membrane and membrane proteins. Fully grown steady-state Chlamydomonas flagella release flagellar vesicles from their tips and failure to resupply membrane should affect flagellar length. To study vesicle release, plasma and flagellar membrane surface proteins were vectorially pulse-labeled and flagella and vesicles were analyzed for biotinylated proteins.

Brefeldin-A destroyed Chlamydomonas Golgi, inhibited the secretory pathway, inhibited flagellar regeneration, and induced full-length flagella to disassemble within 6 hrs, consistent with flagellar disassembly being induced by a failure to resupply membrane.

In contrast to membrane lipids, a pool of biotinylatable membrane proteins was identified that was sufficient to resupply flagella as they released vesicles for 6 hrs in the absence of protein synthesis and to support one and nearly two regenerations of flagella following amputation.

These studies reveal the importance of the secretory pathway to assemble and maintain full-length flagella. Flagellar biosynthesis exerts temporal regulation of secretion of specific Campylobacter jejuni colonization and virulence determinants.

The Campylobacter jejuni flagellum exports both proteins that form the flagellar organelle for swimming motility and colonization and virulence factors that promote commensal colonization of the avian intestinal tract or invasion of human intestinal cells respectively.

We explored how the C. Flagellar biogenesis was observed to exert temporal control of secretion of these proteins, indicating that a bolus of secretion of colonization and virulence factors occurs during hook biogenesis with filament polymerization itself reducing secretion of these factors. Furthermore, we found that intramolecular and intermolecular requirements for flagellar -dependent secretion of these proteins were most reminiscent to those for flagellin secretion.

Importantly, we discovered that secretion of one colonization and virulence factor, CiaI, was not required for invasion of human colonic cells, which counters previous hypotheses for how this protein functions during invasion.

Instead, secretion of CiaI was essential for C. Our work provides insight into the versatility of the bacterial flagellum as a secretory machine that can export proteins promoting diverse biological processes. The Bacillus subtilis flagellar regulatory protein sigma D: Flagellar biosynthesis requires an alternative sigma sigma subunit of RNA polymerase to allow recognition of the promoters for flagellin and other late genes of the flagellar regulon. We have now overproduced and characterized Bacillus subtilis sigma D: Limited protease digestion studies indicate that sigma D contains an amino-terminal domain, comprising conserved regions 1.

The protease-sensitive region between these two domains correlates with a region of very low sequence conservation among bacterial sigma factors. Unlike the primary sigma factor, sigma D binds to DNA. In non-denaturing polyacrylamide gel electrophoresis the sigma D-DNA complex has an apparent equilibrium dissociation constant of 1 microM.

Binding of sigma D to the promoter for flagellin, PD-6, appears to lead to an altered DNA structure near the and recognition elements as detected by DNase I footprinting and by the enhanced reactivity of several bases to dimethylsulfate.

Flagellar synchronization through direct hydrodynamic interactions. Flows generated by ensembles of flagella are crucial to development, motility and sensing, but the mechanisms behind this striking coordination remain unclear. We present novel experiments in which two micropipette-held somatic cells of Volvox carteri, with distinct intrinsic beating frequencies, are studied by high-speed imaging as a function of their separation and orientation.

Analysis of time series shows that the interflagellar coupling, constrained by lack of connections between cells to be hydrodynamical, exhibits a spatial dependence consistent with theory. At close spacings it produces robust synchrony for thousands of beats, while at increasing separations synchrony is degraded by stochastic processes.

Manipulation of the relative flagellar orientation reveals in-phase and antiphase states, consistent with dynamical theories. Flagellar tracking with exquisite precision reveals waveform changes that result from hydrodynamic coupling. This study proves unequivocally that flagella coupled solely through a fluid can achieve robust synchrony despite differences in their intrinsic properties.

For construction of the bacterial flagellum, flagellar proteins are exported via its specific export apparatus from the cytoplasm to the distal end of the growing flagellar structure.

FlhA is a TM export gate protein and plays important roles in energy coupling of protein translocation. However, the energy coupling mechanism remains unknown.

Here, we performed a cross-complementation assay to measure robustness of the energy transduction system of the export apparatus against genetic perturbations. We propose that FliH and FliI ensure robust and efficient energy coupling of protein export during flagellar assembly. Nonlinear amplitude dynamics in flagellar beating. The physical basis of flagellar and ciliary beating is a major problem in biology which is still far from completely understood.

The fundamental cytoskeleton structure of cilia and flagella is the axoneme, a cylindrical array of microtubule doublets connected by passive crosslinkers and dynein motor proteins. The complex interplay of these elements leads to the generation of self-organized bending waves. Although many mathematical models have been proposed to understand this process, few attempts have been made to assess the role of dyneins on the nonlinear nature of the axoneme. Here, we investigate the nonlinear dynamics of flagella by considering an axonemal sliding control mechanism for dynein activity.

This approach unveils the nonlinear selection of the oscillation amplitudes, which are typically either missed or prescribed in mathematical models.

The explicit set of nonlinear equations are derived and solved numerically. Our analysis reveals the spatiotemporal dynamics of dynein populations and flagell With few exceptions, the function of cilia and flagella is to beat rhythmically and set up relative motion between themselves and the liquid that surrounds them. The molecular basis of axonemal movement is understood in considerable detail, with the exception of the mechanism that provides its rhythmical or oscillatory quality.

Some kind of repetitive 'switching' event is assumed to occur; there are several proposals regarding the nature of the 'switch' and how it might operate.

Herein I first summarise all the factors known to influence the rate of the oscillation the beating frequency. Many of these factors exert their effect through modulating the mean sliding velocity between the nine doublet microtubules of the axoneme, this velocity being the determinant of bend growth rate and bend propagation rate. Then I explain six proposed mechanisms for flagellar oscillation and review the evidence on which they are based.

Finally, I attempt to derive an economical synthesis, drawing for preference on experimental research that has been minimally disruptive of the intricate structure of the axoneme.

The 'provisional synthesis' is that flagellar oscillation emerges from an effect of passive sliding direction on the dynein arms. Sliding in one direction facilitates force-generating cycles and dynein-to-dynein synchronisation along a doublet; sliding in the other direction is inhibitory.

The direction of the initial passive sliding normally oscillates because it is controlled hydrodynamically through the alternating direction of the propulsive thrust. However, in the absence of such regulation, there can be a perpetual, mechanical self-triggering through a reversal of sliding direction due to the recoil of elastic structures that deform as a response to the prior active sliding.

This provisional synthesis may be a useful basis for further examination of the problem. Full Text Available Flagella are surface structures critical for motility and virulence of many bacterial species. In Listeria monocytogenes, MogR tightly represses expression of flagellin FlaA during extracellular growth at 37 degrees C and during intracellular infection. MogR is also required for full virulence in a murine model of infection.

Using in vitro and in vivo infection models, we determined that the severe virulence defect of MogR-negative bacteria is due to overexpression of FlaA. Specifically, overproduction of FlaA in MogR-negative bacteria caused pleiotropic defects in bacterial division chaining phenotype, intracellular spread, and virulence in mice.

Analysis of MogR protein levels demonstrated that modulation of MogR repression activity confers the temperature-specificity to flagellar motility gene expression. Epistasis analysis revealed that MogR repression of transcription is antagonized in a temperature-dependent manner by the DegU response regulator and that DegU further regulates FlaA levels through a posttranscriptional mechanism.

These studies provide the first known example to our knowledge of a transcriptional repressor functioning as a master regulator controlling nonhierarchal expression of flagellar motility genes. Scientific experiments are indispensable parts of Biochemistry and Molecular Biology. In this study, a comprehensive Biochemistry and Molecular Biology experiment about "Salmonella enterica" serovar Typhi Flagellar phase variation has been designed.

It consisted of three parts, namely, inducement of bacterial Flagellar phase variation,…. The flagellar adenylate kinases of Trypanosoma cruzi. Adenylate kinases ADK are key enzymes involved in cell energy management. Trypanosomatids present the highest number of variants in a single cell in comparison with the rest of the living organisms.

Interestingly, TcADK1 presents a stage-specific expression. This variant was detected in epimastigotes cells, and was completely absent in trypomastigotes and amastigotes, while TcADK4 is present in the major life cycle stages of T. Both variants are also regulated, in opposite ways, along the parasite growth curve suggesting that their expression depends on the intra- and extracellular conditions.

The presence of ADK variants in the flagellum would be critical for the provision of energy in a process of high ATP consumption such as cell motility.

In situ ellipsometric study of surface immobilization of flagellar filaments. Protein filaments composed of thousands of subunits are promising candidates as sensing elements in biosensors. In this work in situ spectroscopic ellipsometry is applied to monitor the surface immobilization of flagellar filaments. This study is the first step towards the development of layers of filamentous receptors for sensor applications. Surface activation is performed using silanization and a subsequent glutaraldehyde crosslinking.

Structure of the flagellar filament layers immobilized on activated and non-activated Si wafer substrates is determined using a two-layer effective medium model that accounted for the vertical density distribution of flagellar filaments with lengths of nm bound to the surface. The formation of the first interface layer can be explained by the multipoint covalent attachment of the filaments, while the second layer is mainly composed of tail pinned filaments floating upwards with the free parts.

As confirmed by atomic force microscopy, covalent immobilization resulted in an increased surface density compared to absorption. We show that DNA-based self-assembly can serve as a general and flexible tool to construct artificial flagella of several micrometers in length and only tens of nanometers in diameter.

By attaching the DNA flagella to biocompatible magnetic microparticles, we provide a proof of concept demonstration of hybrid structures that, when rotated in an external magnetic field, propel by means of a flagellar bundle, similar to self-propelling peritrichous bacteria. Our theoretical analysis predicts that flagellar bundles that possess a length-dependent bending stiffness should exhibit a superior swimming speed compared to swimmers with a single appendage.

The DNA self-assembly method permits the realization of these improved flagellar bundles in good agreement with our quantitative model. DNA flagella with well-controlled shape could fundamentally increase the functionality of fully biocompatible nanorobots and extend the scope and complexity of active materials. The load-response of the flagellar beat.

We derive a link between the chemo-mechanical efficiency of the flagellar beat and its ability to synchronize to oscillatory flows. The CckA-ChpT-CtrA phosphorelay system is regulated by quorum sensing and controls flagellar motility in the marine sponge symbiont Ruegeria sp. Full Text Available Bacteria respond to their environment via signal transduction pathways, often two-component type systems that function through phosphotransfer to control expression of specific genes.

Phosphorelays are derived from two-component systems but are comprised of additional components. The essential cckA-chpT-ctrA phosphorelay in Caulobacter crescentus has been well studied and is important in orchestrating the cell cycle, polar development and flagellar biogenesis.

Although cckA, chpT and ctrA homologues are widespread among the Alphaproteobacteria, relatively few is known about their function in the large and ecologically significant Roseobacter clade of the Rhodobacterales. In this study the cckA-chpT-ctrA system of the marine sponge symbiont Ruegeria sp. Our results reveal that the cckA, chpT and ctrA genes positively control flagellar biosynthesis.

In contrast to C. KLH11 are non-essential and do not affect bacterial growth. Gene fusion and transcript analyses provide evidence for ctrA autoregulation and the control of motility-related genes. Full Text Available Bactofilins are a widely conserved protein family implicated in cell shape maintenance and in bacterial motility. The proteins are required for the establishment of flagellar hook- and filament structures, but apparently not for the formation of basal bodies.

BacF assemblies are relatively static, and partially colocalize with flagellar basal bodies, while BacE assemblies are fewer per cell than those of BacF and are highly mobile. Tracking of BacE foci showed that the assemblies arrest at a single point for a few hundred milliseconds, showing that a putative interaction with flagellar structures would be transient and fast.

When overexpressed or expressed in a heterologous cell system, bactofilins can form filamentous structures, and also form multimers as purified proteins. Our data reveal a propensity for bactofilins to form filaments, however, in B.

Bactofilins are a widely conserved protein family implicated in cell shape maintenance and in bacterial motility. Full Text Available The flagellar pocket constitutes an active and strategic site in the body of trypanosomatids i.

Most importantly, the flagellar pocket is the unique site of surface protein export and nutrient uptake in trypanosomatids, and thus constitutes a key portal for the interaction with the host. In this work, we identified and characterized a novel Trypanosoma cruzi protein, termed TCLP 1, that accumulates at the flagellar pocket area of parasite replicative forms, as revealed by biochemical, immuno-cytochemistry and electron microscopy techniques. Different in silico analyses revealed that TCLP 1 is the founding member of a family of chimeric molecules restricted to trypanosomatids bearing, in addition to eukaryotic ubiquitin-like and protein-protein interacting domains, a motif displaying significant structural homology to bacterial multi-cargo chaperones involved in the secretion of virulence factors.

Using the fidelity of an homologous expression system we confirmed TCLP 1 sub-cellular distribution and showed that TCLP 1-over-expressing parasites display impaired survival and accelerated progression to late stationary phase under starvation conditions. The reduced endocytic capacity of TCLP 1-over-expressors likely underlies at least in part this growth phenotype.

TCLP 1 is involved in the uptake of extracellular macromolecules required for nutrition and hence in T. Due to the bacterial origin, sub-cellular distribution and putative function s, we propose TCLP 1 and related orthologs in trypanosomatids as appealing therapeutic targets for intervention against these health-threatening parasites. The flagellar pocket constitutes an active and strategic site in the body of trypanosomatids i. Due to the bacterial origin, sub-cellular distribution and putative function s , we propose TCLP 1 and related orthologs in trypanosomatids as appealing therapeutic targets for intervention against these health-threatening parasites.

Type III secretion systems T3SSs are multiprotein molecular devices used by many Gram-negative bacterial pathogens to translocate effector proteins into eukaryotic cells. A T3SS is also used for protein export in flagellar assembly, which promotes bacterial motility.

The two systems are evolutionarily related, possessing highly conserved components in their export apparatuses. Its highly regulated movement is essential for the normal function of many organs; ciliopathies cause congenital defects, chronic respiratory tract infections and infertility. We present an efficient method to obtain a quantitative description of flagellar motion, with high spatial and temporal resolution, from high speed video recording of bright field images.

This highly automated tec Direct evidence of flagellar synchronization through hydrodynamic interactions. Eukaryotic cilia and flagella exhibit striking coordination, from the synchronous beating of two flagella in Chlamydomonas to the metachronal waves and large-scale flows displayed by carpets of cilia. However, the precise mechanisms responsible for flagellar synchronization remain unclear.

We perform a series of experiments involving two individual flagella in a quiescent fluid. Cells are isolated from the colonial alga Volvox carteri, held in place at a fixed distance d, and oriented so that their flagellar beating planes coincide.

In this fashion, we are able to explicitly assess the role of hydrodynamics in achieving synchronization. For closely separated cells, the flagella are capable of exhibiting a phase-locked state for thousands of beats at a time, despite significant differences in their intrinsic frequencies.

The coupling strength extracted through analysis of the synchronization statistics exhibits excellent agreement with hydrodynamic predictions. This study unambiguously reveals that flagella coupled only through hydrodynamics are capable of exhibiting robust synchrony. Probing flagellar promoter occupancy in wild-type and mutant Caulobacter crescentus by chromatin immunoprecipitation.

In the asymmetric predivisional cell of Caulobacter crescentus, TipF and TipN mark the cellular pole for future flagellar development.

TipN is localized to the flagellar pole before TipF and is essential for the proper placement of the flagellum in C. We deduce that TipF contributes to proper expression of flagellar genes in C. Second-chance signal transduction explains cooperative flagellar switching.

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Salmonella enterica is a gram-negative, rod-shaped, flagellated bacterium (figure 1) that is of interest due to its ability to cause infectious disease in humans and animals. (2). Human salmonellosis, S. enterica infection, occurs in about million people per year, an estimated 30% of all food borne illness, causing about deaths and has an . Start studying Gram negative bacteria characteristics. Learn vocabulary, siderophore, adhesions, capsule Salmonella non-typhi groups. Salmonella enterica serovar Paratyphi, efficacy of the Salmonella Typhi Ty21a-vaccine providing utilizing siderophores may also be important.