Modulation of Self-Assembly in Biological Motor Complexes

The flagellum in bacteria is a sensitive detector of perturbations in environmental viscosities. The driver for such sensing of mechanical signals is the flagellar motor, which tailors motility to suit the environment. Mechanosensitive torque-generating elements that rotate the motor detect mechanical signals, and reversibly remodel their assembly in response to changes in the viscous loads. Remodeling likely plays a role in triggering signaling pathways that control cell-morphology and motility. To determine the mechanism of remodeling and its role in signaling, we tested remodeling over varying viscous loads. We subjected wild-type strains and strains that lacked downstream-transducers of mechanical signals to large mechanical stimuli. From the initial speed-response (following the stimulus), we estimated the amount of torque-generated per stator-unit in the presence and absence of the effectors. Subsequent measurements revealed the absence of feedback from downstream effectors on motor remodeling. Although crucial for cell-survival and adaptation, proteins involved in downstream-signaling are unlikely to regulate motor-mechanosensing.