scholarly journals A possible physical mechanism of the torque generation of the bacterial flagellar motor

2020 ◽  
Author(s):  
Y. C. Chou
Keyword(s):  
Cell Membrane ◽  
Drag Force ◽  
Langevin Equation ◽  
Linear Dependence ◽  
Rotational Frequency ◽  
Flagellar Motor ◽  
Impulsive Force ◽  
Step Size ◽  
Frictional Interaction ◽  
Bacterial Flagellar Motor

AbstractThe torque required for the rotation of the rotor of a bacterial flagellar motor (BFM) can be generated from an impulsive force resulting from the collision between the stator and the rotor. The asymmetry in the fluctuations of the tilting angle of the rotor determines the direction of rotation. The expressions of the torque and the step size can be derived from a Langevin equation of motion. The drag coefficient of BFM derived from the Langevin equation and the measured torque–speed (τ-ω) relation is notably high; the viscous force from the environment cannot account for it. The drag force may be caused by the frictional interaction between the bearing-like L- and P-rings of BFM and the cell membrane. Order-of-magnitude estimations of the torque and the step size are consistent with previous experimental observations. The slope of the linear dependence of the rotational frequency on the temperature was estimated and was consistent with the observed value. A simulation device having the structural characteristics of BFM was designed to demonstrate the applicability of the proposed mechanism. Many observations for the actual BFM, such as the bidirectional rotation and the τ-ω relations of the clockwise and counterclockwise rotations, were reproduced in the simulation experiments.ImportanceThe concept that the torque required for the rotation of the rotor of a bacterial flagellar motor (BFM) can be generated from an impulsive force resulting from the collision between the stator and the rotor is new and effective. The magnitude of the torque and the size of the step derived from the proposed mechanism are consistent with the observed values. The torque-speed (τ-ω) relation might be explained by the frequency-dependent drag force caused by the frictional interaction between the bearing-like L- and P-rings of BFM and the cell membrane. The slope of the linear dependence of the rotational frequency on the temperature is consistent with the observed value, which has not been achieved previously.

scholarly journals 2P167 The stator complex of the bacterial flagellar motor senses drag force during motor rotation(The 48th Annual Meeting of the Biophysical Society of Japan)

2010 ◽  
Vol 50 (supplement2) ◽  
pp. S111-S112
Author(s):  
Yong-Suk Che ◽  
Tohru Minamino ◽  
Shuichi Nakamura ◽  
Nobunori Kami-ike ◽  
Keiichi Namba
Keyword(s):  
Annual Meeting ◽  
Drag Force ◽  
Flagellar Motor ◽  
Biophysical Society ◽  
Bacterial Flagellar Motor

Visualization of Functional Rotor Proteins of the Bacterial Flagellar Motor in the Cell Membrane

2007 ◽  
Vol 367 (3) ◽  
pp. 692-701 ◽  
Author(s):  
Hajime Fukuoka ◽  
Yoshiyuki Sowa ◽  
Seiji Kojima ◽  
Akihiko Ishijima ◽  
Michio Homma
Keyword(s):  
Cell Membrane ◽  
Flagellar Motor ◽  
Bacterial Flagellar Motor

scholarly journals The Response of Bacterial Flagellar Motor to Stepwise Increase in NaCl Concentration

2020 ◽  
Author(s):  
V. Soman ◽  
S. Kumari ◽  
S. Nath ◽  
R. Elangovan
Keyword(s):  
Membrane Potential ◽  
Cell Membrane ◽  
Salmonella Enteritidis ◽  
Proton Motive Force ◽  
Motive Force ◽  
Flagellar Motor ◽  
Stepwise Increase ◽  
Flagellar Motors ◽  
Nacl Concentration ◽  
Bacterial Flagellar Motor

AbstractMany species of bacteria use flagella to navigate in its environment. The flagellum is a 7-10 μm long helical filament with a rotary motor at its base embedded in the cell membrane and almost a dozen stator complexes. Proton motive force across the cell membrane powers the flagellar motors of E.coli and Salmonella. The motor stochastically switches between clockwise and counter-clockwise direction. A chemotaxis system causes the motor to change its direction, but the process is more complex as the switch is sensitive to load and proton motive force as well. NaCl is significant with regard to the flagellar motor as it affects the stator dynamics, proton motive force, and osmotaxis at higher concentration. Chemotaxis helps the bacteria for its growth and survival. E.coli’s natural habitat has high osmolarity and the organism uses use various mechanisms for osmoregulation. However, the role of flagellar motor to adapt to the changes in osmolarity, or osmotaxis, is not well studied. In this work, we dissipated the membrane potential of bacteria in pH 7 using step-wise increase in concentration of NaCl in motility buffer and studied the output of E.coli’s flagellar motor using tethered bead assay and swimming Salmonella enteritidis cells. We observed decrease in motor speed and switching rates with stepwise increase in NaCl concentration in the motility buffer. The mean speed of the motors decreased with NaCl concentration. The population of swimming cells tumbled more with increase in concentration of NaCl. At the single motor level, the motors biased to CCW rotation with decrease in membrane potential. In this study, we present our observations of the flagellar motor in high NaCl concentration, and explore how NaCl can be used to study various aspects of the bacterial flagellar motor.Statement of significanceSodium ion has been significant in the both the cellular energetics and the function of bacterial flagellar motor. Growing evidence show that the effect of sodium ions was not what hitherto thought it would be. It is involved in the sodium energetics, dissipate membrane potential, affect the flagellar stator dynamics of bacteria. Being an osmolyte, it influences the osmotaxis of bacteria. In this work, we studied the effect of NaCl on the response of the single bacterial flagellar motor of E.coli and swimming cells of Salmonella enteritidis. We observed that the effect of NaCl on the output of the flagellar motor was significant and it may affect the cells in various ways.

scholarly journals Site-Directed Cross-Linking Identifies the Stator-Rotor Interaction Surfaces in a Hybrid Bacterial Flagellar Motor

2021 ◽  
Vol 203 (9) ◽  
Author(s):  
Hiroyuki Terashima ◽  
Seiji Kojima ◽  
Michio Homma
Keyword(s):  
Escherichia Coli ◽  
Cross Linking ◽  
Physical Interaction ◽  
Flagellar Motor ◽  
Intact Cells ◽  
Content Type ◽  
Bacterial Flagellum ◽  
Cross Links ◽  
Bacterial Flagellar Motor ◽  
Rotary Motor

ABSTRACT The bacterial flagellum is the motility organelle powered by a rotary motor. The rotor and stator elements of the motor are located in the cytoplasmic membrane and cytoplasm. The stator units assemble around the rotor, and an ion flux (typically H+ or Na+) conducted through a channel of the stator induces conformational changes that generate rotor torque. Electrostatic interactions between the stator protein PomA in Vibrio (MotA in Escherichia coli) and the rotor protein FliG have been shown by genetic analyses but have not been demonstrated biochemically. Here, we used site-directed photo-cross-linking and disulfide cross-linking to provide direct evidence for the interaction. We introduced a UV-reactive amino acid, p-benzoyl-l-phenylalanine (pBPA), into the cytoplasmic region of PomA or the C-terminal region of FliG in intact cells. After UV irradiation, pBPA inserted at a number of positions in PomA and formed a cross-link with FliG. PomA residue K89 gave the highest yield of cross-links, suggesting that it is the PomA residue nearest to FliG. UV-induced cross-linking stopped motor rotation, and the isolated hook-basal body contained the cross-linked products. pBPA inserted to replace residue R281 or D288 in FliG formed cross-links with the Escherichia coli stator protein, MotA. A cysteine residue introduced in place of PomA K89 formed disulfide cross-links with cysteine inserted in place of FliG residues R281 and D288 and some other flanking positions. These results provide the first demonstration of direct physical interaction between specific residues in FliG and PomA/MotA. IMPORTANCE The bacterial flagellum is a unique organelle that functions as a rotary motor. The interaction between the stator and rotor is indispensable for stator assembly into the motor and the generation of motor torque. However, the interface of the stator-rotor interaction has only been defined by mutational analysis. Here, we detected the stator-rotor interaction using site-directed photo-cross-linking and disulfide cross-linking approaches. We identified several residues in the PomA stator, especially K89, that are in close proximity to the rotor. Moreover, we identified several pairs of stator and rotor residues that interact. This study directly demonstrates the nature of the stator-rotor interaction and suggests how stator units assemble around the rotor and generate torque in the bacterial flagellar motor.

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