scholarly journals Effect of Intracellular pH on Rotational Speed of Bacterial Flagellar Motors

2003 ◽  
Vol 185 (4) ◽  
pp. 1190-1194 ◽  
Author(s):  
Tohru Minamino ◽  
Yasuo Imae ◽  
Fumio Oosawa ◽  
Yuji Kobayashi ◽  
Kenji Oosawa
Keyword(s):  
Swimming Speed ◽  
Rotational Speed ◽  
Potassium Acetate ◽  
Flagellar Motor ◽  
Weak Acids ◽  
E Coli ◽  
Rotation Rates ◽  
Ph Values ◽  
Flagellar Motors ◽  
External Ph

ABSTRACT Weak acids such as acetate and benzoate, which partially collapse the transmembrane proton gradient, not only mediate pH taxis but also impair the motility of Escherichia coli and Salmonella at an external pH of 5.5. In this study, we examined in more detail the effect of weak acids on motility at various external pH values. A change of external pH over the range 5.0 to 7.8 hardly affected the swimming speed of E. coli cells in the absence of 34 mM potassium acetate. In contrast, the cells decreased their swimming speed significantly as external pH was shifted from pH 7.0 to 5.0 in the presence of 34 mM acetate. The total proton motive force of E. coli cells was not changed greatly by the presence of acetate. We measured the rotational rate of tethered E. coli cells as a function of external pH. Rotational speed decreased rapidly as the external pH was decreased, and at pH 5.0, the motor stopped completely. When the external pH was returned to 7.0, the motor restarted rotating at almost its original level, indicating that high intracellular proton (H+) concentration does not irreversibly abolish flagellar motor function. Both the swimming speeds and rotation rates of tethered cells of Salmonella also decreased considerably when the external pH was shifted from pH 7.0 to 5.5 in the presence of 20 mM benzoate. We propose that the increase in the intracellular proton concentration interferes with the release of protons from the torque-generating units, resulting in slowing or stopping of the motors.

scholarly journals Roles of Charged Residues of Rotor and Stator in Flagellar Rotation: Comparative Study using H+-Driven and Na+-Driven Motors in Escherichia coli

2006 ◽  
Vol 188 (4) ◽  
pp. 1466-1472 ◽  
Author(s):  
Toshiharu Yakushi ◽  
Junghoon Yang ◽  
Hajime Fukuoka ◽  
Michio Homma ◽  
David F. Blair
Keyword(s):  
Escherichia Coli ◽  
Comparative Study ◽  
Electrostatic Interactions ◽  
General Feature ◽  
Flagellar Motor ◽  
Motor Patterns ◽  
E Coli ◽  
Flagellar Motors ◽  
Charged Residues ◽  
Flagellar Rotation

ABSTRACT In Escherichia coli, rotation of the flagellar motor has been shown to depend upon electrostatic interactions between charged residues of the stator protein MotA and the rotor protein FliG. These charged residues are conserved in the Na+-driven polar flagellum of Vibrio alginolyticus, but mutational studies in V. alginolyticus suggested that they are relatively unimportant for motor rotation. The electrostatic interactions detected in E. coli therefore might not be a general feature of flagellar motors, or, alternatively, the V. alginolyticus motor might rely on similar interactions but incorporate additional features that make it more robust against mutation. Here, we have carried out a comparative study of chimeric motors that were resident in E. coli but engineered to use V. alginolyticus stator components, rotor components, or both. Charged residues in the V. alginolyticus rotor and stator proteins were found to be essential for motor rotation when the proteins functioned in the setting of the E. coli motor. Patterns of synergism and suppression in rotor/stator double mutants indicate that the V. alginolyticus proteins interact in essentially the same way as their counterparts in E. coli. The robustness of the rotor-stator interface in V. alginolyticus is in part due to the presence of additional charged residues in PomA but appears mainly due to other factors, because an E. coli motor using both rotor and stator components from V. alginolyticus remained sensitive to mutation. Motor function in V. alginolyticus may be enhanced by the proteins MotX and MotY.

scholarly journals Roles of Charged Residues in the C-Terminal Region of PomA, a Stator Component of the Na+-Driven Flagellar Motor

2008 ◽  
Vol 190 (10) ◽  
pp. 3565-3571 ◽  
Author(s):  
Madoka Obara ◽  
Toshiharu Yakushi ◽  
Seiji Kojima ◽  
Michio Homma
Keyword(s):  
Electrostatic Interactions ◽  
Intramolecular Interactions ◽  
The Other ◽  
Flagellar Motor ◽  
Wild Type ◽  
Mutant Proteins ◽  
E Coli ◽  
Flagellar Motors ◽  
Charged Residues ◽  
Suppressor Analysis

ABSTRACT Bacterial flagellar motors use specific ion gradients to drive their rotation. It has been suggested that the electrostatic interactions between charged residues of the stator and rotor proteins are important for rotation in Escherichia coli. Mutational studies have indicated that the Na+-driven motor of Vibrio alginolyticus may incorporate interactions similar to those of the E. coli motor, but the other electrostatic interactions between the rotor and stator proteins may occur in the Na+-driven motor. Thus, we investigated the C-terminal charged residues of the stator protein, PomA, in the Na+-driven motor. Three of eight charge-reversing mutations, PomA(K203E), PomA(R215E), and PomA(D220K), did not confer motility either with the motor of V. alginolyticus or with the Na+-driven chimeric motor of E. coli. Overproduction of the R215E and D220K mutant proteins but not overproduction of the K203E mutant protein impaired the motility of wild-type V. alginolyticus. The R207E mutant conferred motility with the motor of V. alginolyticus but not with the chimeric motor of E. coli. The motility with the E211K and R232E mutants was similar to that with wild-type PomA in V. alginolyticus but was greatly reduced in E. coli. Suppressor analysis suggested that R215 may participate in PomA-PomA interactions or PomA intramolecular interactions to form the stator complex.

scholarly journals Antimicrobial silver inhibits bacterial movement and stalls flagellar motor

2020 ◽  
Author(s):  
Benjamin Russell ◽  
Ariel Rogers ◽  
Matthew Kurilich ◽  
Venkata Rao Krishnamurthi ◽  
Jingyi Chen ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Direct Evidence ◽  
Antimicrobial Activities ◽  
Bacterial Virulence ◽  
Bacterial Motility ◽  
Flagellar Motor ◽  
E Coli ◽  
Flagellar Motors ◽  
Quantitative Understanding ◽  
Bacterial Movement

AbstractSilver (Ag) has been gaining broad attention due to their antimicrobial activities and the increasing resistance of bacteria to commonly prescribed antibiotics. However, various aspects of the antimicrobial mechanism of Ag have not been understood, including how silver affects the motility of bacteria, a factor that is intimately related to bacterial virulence. Here we report our study on the antibiotic effects of Ag+ ions on the motility of E. coli bacteria using swimming and tethering assays. We observed that the bacteria slowed down dramatically when subjected to Ag+ ions, providing direct evidence showing that Ag inhibits the motility of bacteria. In addition, through tethering assays, we monitored the rotation of flagellar motors and observed that the tumbling frequency of bacteria increased significantly in the presence of Ag+ ions. Furthermore, the rotation of bacteria in the tethering assays were analyzed using hidden Markov model (HMM); and we found that Ag+-treatment led to a significant decrease in the tumbling-to-running transition rate of the bacteria, suggesting that the rotation of bacterial flagellar motors was stalled by Ag+ ions. This work provided a new quantitative understanding on the mechanism of Ag-based antimicrobial agents in bacterial motility.

scholarly journals A Chimeric N-Terminal Escherichia coli-C-Terminal Rhodobacter sphaeroides FliG Rotor Protein Supports Bidirectional E. coli Flagellar Rotation and Chemotaxis

2005 ◽  
Vol 187 (5) ◽  
pp. 1695-1701 ◽  
Author(s):  
Karen A. Morehouse ◽  
Ian G. Goodfellow ◽  
R. Elizabeth Sockett
Keyword(s):  
Escherichia Coli ◽  
Rhodobacter Sphaeroides ◽  
Protein Interactions ◽  
Flagellar Motor ◽  
E Coli ◽  
C Terminus ◽  
Flagellar Motors ◽  
Serovar Typhimurium ◽  
Essential Function ◽  
Flagellar Rotation

ABSTRACT Flagellate bacteria such as Escherichia coli and Salmonella enterica serovar Typhimurium typically express 5 to 12 flagellar filaments over their cell surface that rotate in clockwise (CW) and counterclockwise directions. These bacteria modulate their swimming direction towards favorable environments by biasing the direction of flagellar rotation in response to various stimuli. In contrast, Rhodobacter sphaeroides expresses a single subpolar flagellum that rotates only CW and responds tactically by a series of biased stops and starts. Rotor protein FliG transiently links the MotAB stators to the rotor, to power rotation and also has an essential function in flagellar export. In this study, we sought to determine whether the FliG protein confers directionality on flagellar motors by testing the functional properties of R. sphaeroides FliG and a chimeric FliG protein, EcRsFliG (N-terminal and central domains of E. coli FliG fused to an R. sphaeroides FliG C terminus), in an E. coli FliG null background. The EcRsFliG chimera supported flagellar synthesis and bidirectional rotation; bacteria swam and tumbled in a manner qualitatively similar to that of the wild type and showed chemotaxis to amino acids. Thus, the FliG C terminus alone does not confer the unidirectional stop-start character of the R. sphaeroides flagellar motor, and its conformation continues to support tactic, switch-protein interactions in a bidirectional motor, despite its evolutionary history in a bacterium with a unidirectional motor.

scholarly journals Correlation of Intracellular Trehalose Concentration with Desiccation Resistance of Soil Escherichia coli Populations

2012 ◽  
Vol 78 (20) ◽  
pp. 7407-7413 ◽  
Author(s):  
Qian Zhang ◽  
Tao Yan
Keyword(s):  
Escherichia Coli ◽  
De Novo ◽  
Potassium Acetate ◽  
Desiccation Stress ◽  
Desiccation Resistance ◽  
Content Type ◽  
Soil Desiccation ◽  
E Coli ◽  
Organic Solute ◽  
Trehalose Synthesis

ABSTRACTNaturalized soilEscherichia colipopulations need to resist common soil desiccation stress in order to inhabit soil environments. In this study, four representative soilE. colistrains and one lab strain, MG1655, were tested for desiccation resistance via die-off experiments in sterile quartz sand under a potassium acetate-induced desiccation condition. The desiccation stress caused significantly lower die-off rates of the four soil strains (0.17 to 0.40 day−1) than that of MG1655 (0.85 day−1). Cellular responses, including extracellular polymeric substance (EPS) production, exogenous glycine betaine (GB) uptake, and intracellular compatible organic solute synthesis, were quantified and compared under the desiccation and hydrated control conditions. GB uptake appeared not to be a specific desiccation response, while EPS production showed considerable variability among theE. colistrains. AllE. colistrains produced more intracellular trehalose, proline, and glutamine under the desiccation condition than the hydrated control, and only the trehalose concentration exhibited a significant correlation with the desiccation-contributed die-off coefficients (Spearman's ρ = −1.0;P= 0.02).De novotrehalose synthesis was further determined for 15E. colistrains from both soil and nonsoil sources to determine its prevalence as a specific desiccation response. MostE. colistrains (14/15) synthesized significantly more trehalose under the desiccation condition, and the soilE. colistrains produced more trehalose (106.5 ± 44.9 μmol/mg of protein [mean ± standard deviation]) than the nonsoil reference strains (32.5 ± 10.5 μmol/mg of protein).

FATE OF COLIFORMS IN YOGURT, BUTTERMILK, SOUR CREAM, AND COTTAGE CHEESE DURING REFRIGERATED STORAGE1

1971 ◽  
Vol 34 (1) ◽  
pp. 54-58 ◽  
Author(s):  
M. C. Goel ◽  
D. C. Kulshrestha ◽  
E. H. Marth ◽  
D. W. Francis ◽  
J. G. Bradshaw ◽  
...  
Keyword(s):  
Substantial Reduction ◽  
Enterobacter Aerogenes ◽  
Cottage Cheese ◽  
Rapid Decline ◽  
Initial Value ◽  
E Coli ◽  
Ph Values ◽  
Test Culture ◽  
Marked Decline ◽  
Sour Cream

Aerobacter (Enterobacter) aerogenes and Escherichia coli were inoculated separately into commercially produced samples of yogurt, buttermilk, sour cream, and cottage cheese. Inoculated products were stored at 7.2 C and were tested daily for up to 10 days to determine changes in numbers of coliforms and in pH values. The number of viable coliforms in yogurt declined dramatically and was markedly different from the initial value after only 24 hr of storage. Usually, survival of coliforms in yogurt did not exceed 3 days of holding. In buttermilk, most often a marked decline in numbers of coliforms was evident after 24 hr of storage. A substantial reduction in numbers (>50% of organisms present initially) of A. aerogenes B199 occurred in sour cream during the first 24 hr of storage, but a similar decline in numbers of E. coli and A. aerogenes FD was not evident until after 3 days of storage. Changes in numbers of E. coli and A. aerogenes in cottage cheese generally were not as rapid as in other products during the first days of storage. A few cottage cheese samples, however, did support rapid increases in test culture numbers. Because of the rapid decline in numbers of coliforms in yogurt, buttermilk, and sour cream, the provision in Standard Methods for the Examination of Dairy Products that permits examination of some of these products for up to 48 hr after manufacture seems inadvisable.

scholarly journals The presence and absence of periplasmic rings in bacterial flagellar motors correlates with stator type

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Mohammed Kaplan ◽  
Debnath Ghosal ◽  
Poorna Subramanian ◽  
Catherine M Oikonomou ◽  
Andreas Kjaer ◽  
...  
Keyword(s):  
Legionella Pneumophila ◽  
Pathogenic Bacteria ◽  
Bioinformatics Analysis ◽  
Cell Envelope ◽  
Shewanella Oneidensis ◽  
Flagellar Motor ◽  
Flagellar Motors ◽  
A Cell ◽  
Animal Hosts

The bacterial flagellar motor, a cell-envelope-embedded macromolecular machine that functions as a cellular propeller, exhibits significant structural variability between species. Different torque-generating stator modules allow motors to operate in different pH, salt or viscosity levels. How such diversity evolved is unknown. Here, we use electron cryo-tomography to determine the in situ macromolecular structures of three Gammaproteobacteria motors: Legionella pneumophila, Pseudomonas aeruginosa, and Shewanella oneidensis, providing the first views of intact motors with dual stator systems. Complementing our imaging with bioinformatics analysis, we find a correlation between the motor’s stator system and its structural elaboration. Motors with a single H+-driven stator have only the core periplasmic P- and L-rings; those with dual H+-driven stators have an elaborated P-ring; and motors with Na+ or Na+/H+-driven stators have both their P- and L-rings embellished. Our results suggest an evolution of structural elaboration that may have enabled pathogenic bacteria to colonize higher-viscosity environments in animal hosts.

scholarly journals Only One of the Five CheY Homologs in Vibrio cholerae Directly Switches Flagellar Rotation

2005 ◽  
Vol 187 (24) ◽  
pp. 8403-8410 ◽  
Author(s):  
Akihiro Hyakutake ◽  
Michio Homma ◽  
Melissa J. Austin ◽  
Markus A. Boin ◽  
Claudia C. Häse ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Gene Clusters ◽  
Swimming Behavior ◽  
Phosphoryl Group ◽  
Flagellar Motor ◽  
Response Regulators ◽  
E Coli ◽  
Control Functions ◽  
Flagellar Rotation ◽  
Principal Roles

ABSTRACT Vibrio cholerae has three sets of chemotaxis (Che) proteins, including three histidine kinases (CheA) and four response regulators (CheY) that are encoded by three che gene clusters. We deleted the cheY genes individually or in combination and found that only the cheY3 deletion impaired chemotaxis, reinforcing the previous conclusion that che cluster II is involved in chemotaxis. However, this does not exclude the involvement of the other clusters in chemotaxis. In other bacteria, phospho-CheY binds directly to the flagellar motor to modulate its rotation, and CheY overexpression, even without CheA, causes extremely biased swimming behavior. We reasoned that a V. cholerae CheY homolog, if it directly controls flagellar rotation, should also induce extreme swimming behavior when overproduced. This was the case for CheY3 (che cluster II). However, no other CheY homolog, including the putative CheY (CheY0) protein encoded outside the che clusters, affected swimming, demonstrating that these CheY homologs cannot act directly on the flagellar motor. CheY4 very slightly enhanced the spreading of an Escherichia coli cheZ mutant in semisolid agar, raising the possibility that it can affect chemotaxis by removing a phosphoryl group from CheY3. We also found that V. cholerae CheY3 and E. coli CheY are only partially exchangeable. Mutagenic analyses suggested that this may come from coevolution of the interacting pair of proteins, CheY and the motor protein FliM. Taken together, it is likely that the principal roles of che clusters I and III as well as cheY0 are to control functions other than chemotaxis.

scholarly journals Effect of the MotA(M206I) Mutation on Torque Generation and Stator Assembly in theSalmonellaH+-Driven Flagellar Motor

2019 ◽  
Vol 201 (6) ◽  
Author(s):  
Yuya Suzuki ◽  
Yusuke V. Morimoto ◽  
Kodai Oono ◽  
Fumio Hayashi ◽  
Kenji Oosawa ◽  
...  
Keyword(s):  
Ion Flux ◽  
Motive Force ◽  
Flagellar Motor ◽  
Wild Type ◽  
Torque Generation ◽  
Unit Speed ◽  
Bacterial Flagellar Motor ◽  
Ph Dependent ◽  
Type Motor ◽  
External Ph

ABSTRACTThe bacterial flagellar motor is composed of a rotor and a dozen stators and converts the ion flux through the stator into torque. Each stator unit alternates in its attachment to and detachment from the rotor even during rotation. In some species, stator assembly depends on the input energy, but it remains unclear how an electrochemical potential across the membrane (e.g., proton motive force [PMF]) or ion flux is involved in stator assembly dynamics. Here, we focused on pH dependence of a slow motile MotA(M206I) mutant ofSalmonella. The MotA(M206I) motor produces torque comparable to that of the wild-type motor near stall, but its rotation rate is considerably decreased as the external load is reduced. Rotation assays of flagella labeled with 1-μm beads showed that the rotation rate of the MotA(M206I) motor is increased by lowering the external pH whereas that of the wild-type motor is not. Measurements of the speed produced by a single stator unit using 1-μm beads showed that the unit speed of the MotA(M206I) is about 60% of that of the wild-type and that a decrease in external pH did not affect the MotA(M206I) unit speed. Analysis of the subcellular stator localization revealed that the number of functional stators is restored by lowering the external pH. The pH-dependent improvement of stator assembly was observed even when the PMF was collapsed and proton transfer was inhibited. These results suggest that MotA-Met206 is responsible for not only load-dependent energy coupling between the proton influx and rotation but also pH-dependent stator assembly.IMPORTANCEThe bacterial flagellar motor is a rotary nanomachine driven by the electrochemical transmembrane potential (ion motive force). About 10 stators (MotA/MotB complexes) are docked around a rotor, and the stator recruitment depends on the load, ion motive force, and coupling ion flux. The MotA(M206I) mutation slows motor rotation and decreases the number of docked stators inSalmonella. We show that lowering the external pH improves the assembly of the mutant stators. Neither the collapse of the ion motive force nor a mutation mimicking the proton-binding state inhibited stator localization to the motor. These results suggest that MotA-Met206 is involved in torque generation and proton translocation and that stator assembly is stabilized by protonation of the stator.

scholarly journals Biphasic chemotaxis ofEscherichia colito the microbiota metabolite indole

2020 ◽  
Vol 117 (11) ◽  
pp. 6114-6120 ◽  
Author(s):  
Jingyun Yang ◽  
Ravi Chawla ◽  
Kathy Y. Rhee ◽  
Rachit Gupta ◽  
Michael D. Manson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Microbial Communities ◽  
Bacterial Chemotaxis ◽  
Dynamic Responses ◽  
Time Dependent ◽  
Flagellar Motor ◽  
Wild Type ◽  
Gi Tract ◽  
Flagellar Motors

Bacterial chemotaxis to prominent microbiota metabolites such as indole is important in the formation of microbial communities in the gastrointestinal (GI) tract. However, the basis of chemotaxis to indole is poorly understood. Here, we exposedEscherichia colito a range of indole concentrations and measured the dynamic responses of individual flagellar motors to determine the chemotaxis response. Below 1 mM indole, a repellent-only response was observed. At 1 mM indole and higher, a time-dependent inversion from a repellent to an attractant response was observed. The repellent and attractant responses were mediated by the Tsr and Tar chemoreceptors, respectively. Also, the flagellar motor itself mediated a repellent response independent of the receptors. Chemotaxis assays revealed that receptor-mediated adaptation to indole caused a bipartite response—wild-type cells were attracted to regions of high indole concentration if they had previously adapted to indole but were otherwise repelled. We propose that indole spatially segregates cells based on their state of adaptation to repel invaders while recruiting beneficial resident bacteria to growing microbial communities within the GI tract.

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