Switching Statistics of a Flagellar Motor: First-Passage Time and Dynamic Binding

Abstract

Bacterial chemotaxis relies on the clockwise-to-counterclockwise switching (and the reverse CCW-to-CW switching) of the flagellar motor’s rotational direction. Yet, despite its central role, the switch mechanism remains poorly understood. Here we study the switch statistics of the flagellar motor using computer simulations that combine first-passage time ideas and the property of dynamic binding of CheY-P to FliM. The simulated clockwise bias and switching frequency as a function of CheY-P concentration agree with the experimental results for E. coli. Moreover, the simulation results show a robust peak, which is present in some experimental reports, in the distribution of the time intervals of both clockwise and counterclockwise rotation.