Computing the motor torque of Escherichia coli

Abstract

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 (Darnton et al., J. Bacteriology, 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 pNnm to 829 pNnm, depending critically on the distance between the flagellar filaments and the nearby surface.

References in corpus (7)

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• Bacterial hydrodynamics
• Swimming Efficiency of Bacterium Escherichia Coli
• Modelling the Mechanics and Hydrodynamics of Swimming E. coli
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Cited by in corpus (7)

• The Bank Of Swimming Organisms at the Micron Scale (BOSO-Micro)
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• An integral-based spectral method for inextensible slender fibers in Stokes flow
• Local drag of a slender rod parallel to a plane wall in a viscous fluid
• Geometric phase methods with Stokes theorem for a general viscous swimmer
• Mapping flagellated swimmers to surface-slip driven swimmers
• A swimming bacterium in a two-fluid model of a polymer solution