The Bacterial Flagellar Motor: Insights Into Torque Generation, Rotational Switching, and Mechanosensing

Guo, Shuaiqi; Li, Jun

doi:10.3389/fmicb.2022.911114

Cited by 14 publications

(14 citation statements)

References 83 publications

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“…This clustering based on MotB-MotB dimer stability could be further examined in greater detail, for example, with regard to species that have specific high-torque operating environments, eg Spirochaetes sp.. These species typically have large rotors to generate larger torques 5,[26][27][28] , but there could be signatures of conservation of increased stator stability elsewhere that may correlate with high-torque or viscous operating conditions.…”

Section: Discussionmentioning

confidence: 99%

“…A crucial component of this complex is the stator subunit which is responsible for the torque-generating step of the motor 3,4 . In E. coli , the stator subunit is in fact composed of two transmembrane (TM) proteins (MotA and MotB) which assemble around the basal rotor of the flagellar motor and form a proton channel at their interface 5 . The inward flux of ions across the complex is efficiently coupled to a mechanical stimulus applied onto the rotor protein FliG which ultimately drives the rotation of a single flagellum 6 .…”

Section: Introductionmentioning

confidence: 99%

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Tuning the stator subunit of the flagellar motor with coiled-coil engineering

Ridone

Winter

Baker

2023

Preprint

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Many bacteria swim driven by an extracellular filament rotated by the bacterial flagellar motor. This motor is powered by the stator complex, MotA5MotB2, a heterodimeric complex which forms an ion channel which couples energy from the ion motive force to torque generation. Recent structural work revealed that stator complex consists of a ring of five MotAs which rotate around a central dimer of MotBs. Transmembrane (TM) domains TM3 and TM4 from MotA combine with the single TM domain from MotB to form two separate ion channels in this complex. Much is known about the ion binding site and specificity, however to-date no modelling has been undertaken to explore the MotB-MotB dimer stability and the role of MotB mobility during rotation. Here we modelled the central MotB dimer using coiled-coil engineering and modelling principles and calculated free energies (BUDE) to identify stable states in the operating cycle of the stator. We found 3 stable coiled-coil states with interface angles 28°, 56° and 64°. We tested the effect of strategic mutagenesis on the comparative energy of the states and correlated motility with a specific hierarchy of stability between the three states. In general, our results indicate agreement with existing models describing a 36° rotation step of the MotA pentameric ring during the power stroke and provide an energetic basis for the coordinated rotation of the central MotB dimer based on coiled-coil modelling.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tuning the stator subunit of the flagellar motor with coiled-coil engineering

Ridone

Winter

Baker

2023

Preprint

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“…The IMF in bacteria can consist of a proton and/or a Na + gradient. Stator proteins of the flagellar motor are specific either for a proton motive force or for a sodium motive force ( Chang et al, 2021 ; Guo and Liu, 2022 ). They translocate ions through a channel to the inner membrane site and convert the electrochemical gradient into torque, which ultimately leads to rotation of the rotor unit ( Biquet-Bisquert et al, 2021 ).…”

Section: Discussionmentioning

confidence: 99%

Clostridioides difficile minimal nutrient requirements for flagellar motility

et al. 2023

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As many gastro-intestinal pathogens, the majority of Clostridioides difficile strains express flagella together with a complete chemotaxis system. The resulting swimming motility is likely contributing to the colonization success of this important pathogen. In contrast to the well investigated general energy metabolism of C. difficile, little is known about the metabolic requirements for maintaining the ion motive force across the membrane, which in turn powers the flagellar motor. We studied here systematically the effect of various amino acids and carbohydrates on the swimming velocity of C. difficile using video microscopy in conjunction with a software based quantification of the swimming speed. Removal of individual amino acids from the medium identified proline and cysteine as the most important amino acids that power swimming motility. Glycine, which is as proline one of the few amino acids that are reduced in Stickland reactions, was not critical for swimming motility. This suggests that the ion motive force that powers the flagellar motor, is critically depending on proline reduction. A maximal and stable swimming motility was achieved with only four compounds, including the amino acids proline, cysteine and isoleucine together with a single, but interchangeable carbohydrate source such as glucose, succinate, mannose, ribose, pyruvate, trehalose, or ethanolamine. We expect that the identified “minimal motility medium” will be useful in future investigations on the flagellar motility and chemotactic behavior in C. difficile, particularly for the unambiguous identification of chemoattractants.

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“…The predominant perception still continues to be the ion-motive force logic (Biquet-Bisquert et al, 2021) and as of now, intricate details of BFS from diverse bacteria are known (Beeby et al, 2020;Tan et al, 2021). Yet, several fundamental aspects/details of the mechanism of powering and electro-mechanical transduction remain elusive (Guo & Liu, 2022;Mondino et al, 2022;Thormann, 2022).…”

Section: Figure 2: Comparison Of the Approximate Dimensions Of Three ...mentioning

confidence: 99%

Questioning physiological rotary functionality in the bacterial flagellar system and proposing a murburn model for motility

Manoj¹,

Jacob²,

Kavdia³

et al. 2022

Preprint

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Bacterial flagellar system (BFS) was the first perceived example of a ‘natural rotary-motor” functionality, mandating the translation of a circular motion of components inside into a linear displacement of the cell body outside. This outcome is supposedly orchestrated with the following features of the BFS: (i) A chemical/electrical differential generates proton motive force (pmf, including a trans-membrane potential, TMP), which is electro-mechanically transduced by inward movement of protons via BFS. (ii) Membrane-bound roteins of BFS serve as stators and the slender filament acts as an external propeller, culminating into a hook-rod that pierces the membrane to connect to a ‘broader assembly of deterministically movable rotor’. We had disclaimed the purported pmf/TMP-based respiratory/photosynthetic physiology involving Complex V, which was also perceived as a “rotary machine” earlier. We pointed out that the murburn redox logic was operative therein. In the context of BFS, we pursue the following similar perspectives: (i) Low probability for the evolutionary attainment of an ordered/synchronized teaming of about two dozen types of proteins (assembled across five-seven distinct phases) towards the singular agendum of rotary motility. (ii) Vital redox activity (not the gambit of pmf/TMP!) powers the molecular and macroscopic activities of cells, including flagella. (iii) Flagellar movement is noted even in ambiances lacking/countering the directionality mandates sought by pmf/TMP. (iv) Structural features of BFS lack component(s) capable of harnessing/achieving pmf/TMP and functional rotation. Falling short of disproving rotability, a viable murburn model for conversion of molecular/biochemical activity into macroscopic/mechanical outcomes is proposed herein for understanding BFS-assisted motility.

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The Bacterial Flagellar Motor: Insights Into Torque Generation, Rotational Switching, and Mechanosensing

Cited by 14 publications

References 83 publications

Tuning the stator subunit of the flagellar motor with coiled-coil engineering

Tuning the stator subunit of the flagellar motor with coiled-coil engineering

Clostridioides difficile minimal nutrient requirements for flagellar motility

Questioning physiological rotary functionality in the bacterial flagellar system and proposing a murburn model for motility

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