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Issue 29, 2018
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Computing the motor torque of Escherichia coli

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The rotary motor of bacteria is a natural nano-technological marvel that enables cell locomotion by powering the rotation of semi-rigid helical flagellar filaments in fluid environments. It is well known that the motor operates essentially at constant torque in counter-clockwise direction but past work have reported a large range of values of this torque. Focusing on Escherichia coli cells that are swimming and cells that are stuck on a glass surface for which all geometrical and environmental parameters are known (N. C. Darnton et al., J. Bacteriol., 2007, 189, 1756–1764), we use two validated numerical methods to compute the value of the motor torque consistent with experiments. Specifically, we use (and compare) a numerical method based on the boundary integral representation of Stokes flow and also develop a hybrid method combining boundary element and slender body theory to model the cell body and flagellar filament, respectively. Using measured rotation speed of the motor, our computations predict a value of the motor torque in the range 440 pN nm to 829 pN nm, depending critically on the distance between the flagellar filaments and the nearby surface.

Graphical abstract: Computing the motor torque of Escherichia coli

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Publication details

The article was received on 15 Mar 2018, accepted on 02 Jun 2018 and first published on 04 Jun 2018

Article type: Paper
DOI: 10.1039/C8SM00536B
Citation: Soft Matter, 2018,14, 5955-5967
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    Computing the motor torque of Escherichia coli

    D. Das and E. Lauga, Soft Matter, 2018, 14, 5955
    DOI: 10.1039/C8SM00536B

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