8.4 The Rotary Bacterial Flagellar Motor

Sowa, Yoshiyuki; Berry, Richard M.

doi:10.1016/b978-0-12-374920-8.00805-5

Cited by 2 publications

(1 citation statement)

References 200 publications

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“…The result of our measurement is consistent with several previously reported values20. However, its numerical value is lower than a separate direct stall torque measurement of 4500 pN·nm19 which, however, appears to be an outlier in the published literature27. Our measurement also falls below indirect, extrapolated estimates of 1260 pN·nm28.…”

Section: Resultssupporting

confidence: 91%

Applying torque to the Escherichia coli flagellar motor using magnetic tweezers

Oene

Dickinson

Cross

et al. 2017

Sci Rep

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The bacterial flagellar motor of Escherichia coli is a nanoscale rotary engine essential for bacterial propulsion. Studies on the power output of single motors rely on the measurement of motor torque and rotation under external load. Here, we investigate the use of magnetic tweezers, which in principle allow the application and active control of a calibrated load torque, to study single flagellar motors in Escherichia coli. We manipulate the external load on the motor by adjusting the magnetic field experienced by a magnetic bead linked to the motor, and we probe the motor’s response. A simple model describes the average motor speed over the entire range of applied fields. We extract the motor torque at stall and find it to be similar to the motor torque at drag-limited speed. In addition, use of the magnetic tweezers allows us to force motor rotation in both forward and backward directions. We monitor the motor’s performance before and after periods of forced rotation and observe no destructive effects on the motor. Our experiments show how magnetic tweezers can provide active and fast control of the external load while also exposing remaining challenges in calibration. Through their non-invasive character and straightforward parallelization, magnetic tweezers provide an attractive platform to study nanoscale rotary motors at the single-motor level.

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