The flagellar motor of Caulobacter crescentus generates more torque when a cell swims backwards

Lele, Pushkar P.; Roland, Thibault; Shrivastava, Abhishek; Chen, Yihao; Berg, Howard C.

doi:10.1038/nphys3528

Cited by 31 publications

(28 citation statements)

References 25 publications

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“…Videos of tethered cells were analyzed with custom-written codes in MATLAB to find the rotational speed as a function of time ( Lele et al, 2015a ). Time-averaged CW bias values were determined for each tethered motor over the duration of 1–2 min.…”

Section: Methodsmentioning

confidence: 99%

Switching and Torque Generation in Swarming E. coli

et al. 2018

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Escherichia coli swarm on semi-solid surfaces with the aid of flagella. It has been hypothesized that swarmer cells overcome the increased viscous drag near surfaces by developing higher flagellar thrust and by promoting surface wetness with the aid of a flagellar switch. The switch enables reversals between clockwise (CW) and counterclockwise (CCW) directions of rotation of the flagellar motor. Here, we measured the behavior of flagellar motors in swarmer cells. Results indicated that although the torque was similar to that in planktonic cells, the tendency to rotate CCW was higher in swarmer cells. This suggested that swarmers likely have a smaller pool of phosphorylated CheY. Results further indicated that the upregulation of the flagellin gene was not critical for flagellar thrust or swarming. Consistent with earlier reports, moisture added to the swarm surface restored swarming in a CCW-only mutant, but not in a FliG mutant that rotated motors CW-only (FliGCW). Fluorescence assays revealed that FliGCW cells grown on agar surfaces carried fewer flagella than planktonic FliGCW cells. The surface-dependent reduction in flagella correlated with a reduction in the number of putative flagellar preassemblies. These results hint toward a possibility that the conformational dynamics of switch proteins play a role in the proper assembly of flagellar complexes and flagellar export, thereby aiding bacterial swarming.

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Section: Methodsmentioning

confidence: 99%

Switching and Torque Generation in Swarming E. coli

et al. 2018

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“…Importantly, the transition to active turbulence as well as the buildup of pretransitional swimmer-swimmer correlations strongly depend on the sign of the force dipole [10,20], where active turbulence is only present for rearactuated "pusher" microswimmers such as most bacteria. Their front-actuated counterpart, "puller" microswimmers, are less common in nature: the bacterium Caulobacter crescentus is able to switch between pusher and puller propulsion modes [21], and the front-actuated alga Chlamydomonas oscillates between pusher and puller modes during its flagellar beat cycle [22,23]. While pure puller suspensions show no collective motion, models incorporating puller flow fields combined with shortranged excluded volume interactions have been observed to induce a polar flocking state, both in pure puller suspensions [24][25][26] and in puller suspensions doped with a small pusher component [27].…”

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confidence: 99%

Symmetric Mixtures of Pusher and Puller Microswimmers Behave as Noninteracting Suspensions

et al. 2020

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Suspensions of rear-and front-actuated microswimmers immersed in a fluid, known respectively as "pushers" and "pullers," display qualitatively different collective behaviors: beyond a characteristic density, pusher suspensions exhibit a hydrodynamic instability leading to collective motion known as active turbulence, a phenomenon which is absent for pullers. In this Letter, we describe the collective dynamics of a binary pusher-puller mixture using kinetic theory and large-scale particle-resolved simulations. We derive and verify an instability criterion, showing that the critical density for active turbulence moves to higher values as the fraction χ of pullers is increased and disappears for χ ≥ 0.5. We then show analytically and numerically that the two-point hydrodynamic correlations of the 1∶1 mixture are equal to those of a suspension of noninteracting swimmers. Strikingly, our numerical analysis furthermore shows that the full probability distribution of the fluid velocity fluctuations collapses onto the one of a noninteracting system at the same density, where swimmer-swimmer correlations are strictly absent. Our results thus indicate that the fluid velocity fluctuations in 1∶1 pusher-puller mixtures are exactly equal to those of the corresponding noninteracting suspension at any density, a surprising cancellation with no counterpart in equilibrium longrange interacting systems.

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“…3g ). For a distance r between the power stroke of the active leg and the tethered point to the glass, the torque was calculated by the following equation: T = r × F , where T is the torque, and F is the thrust of the leg 26 . With this model, bidirectional rotation could be produced depending on the geometry between the tethering point and the active leg.…”

Section: Discussionmentioning

confidence: 99%

Linear motor driven-rotary motion of a membrane-permeabilized ghost in Mycoplasma mobile

Kinosita

Miyata

Nishizaka

2018

Sci Rep

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Mycoplasma mobile exhibits a smooth gliding movement as does its membrane-permeabilized ghost model. Ghost experiments revealed that the energy source for M. mobile motility is adenosine triphosphate (ATP) and that the gliding comprises repetitions of 70 nm steps. Here we show a new motility mode, in which the ghost model prepared with 0.013% Triton X-100 exhibits directed rotational motions with an average speed of approximately 2.1 Hz when ATP concentration is greater than 3.0 × 10−1 mM. We found that rotary ghosts treated with sialyllactose, the binding target for leg proteins, were stopped. Although the origin of the rotation has not been conclusively determined, this result suggested that biomolecules embedded on the cell membrane nonspecifically attach to the glass and work as a fluid pivot point and that the linear motion of the leg is a driving force for the rotary motion. This simple geometry exemplifies the new motility mode, by which the movement of a linear motor is efficiently converted to a constant rotation of the object on a micrometer scale.

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The flagellar motor of Caulobacter crescentus generates more torque when a cell swims backwards

Cited by 31 publications

References 25 publications

Switching and Torque Generation in Swarming E. coli

Switching and Torque Generation in Swarming E. coli

Symmetric Mixtures of Pusher and Puller Microswimmers Behave as Noninteracting Suspensions

Linear motor driven-rotary motion of a membrane-permeabilized ghost in Mycoplasma mobile

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