Mechanism for dissipative driving of rotation switching in the bacterial flagellar motor

Determine the physical mechanism responsible for the non-equilibrium, dissipative driving of rotation-direction switching in the bacterial flagellar motor, identifying how switching is coupled to energy dissipation within the motor.

Background

Experiments measuring single-motor switching dynamics revealed peaked dwell-time distributions, which cannot be generated by any equilibrium process. This implies that the bacterial flagellar motor’s rotation switching must be driven by energy dissipation, most likely via the ion motive force that powers rotation.

Prior models invoked conformational spread (equilibrium nearest-neighbor coupling among FliM/FliG subunits) to explain ultrasensitivity, but they do not account for the observed non-equilibrium features. Although various non-equilibrium modifications have been added to these models, the specific physical mechanism that couples rotation switching to dissipation has remained an explicit unknown. This paper proposes Global Mechanical Coupling (GMC) as a candidate mechanism, but its definitive identification and validation remain open.