Flow sensing in the bacterial flagellar motor of <i>E. Coli</i>

E. coli swims by rotating several flagella randomly distributed along the cell body. At the base of each flagellum is the bacterial flagellar motor, a rotary molecular protein complex that couples the proton motive force to the rotation of flagellar filaments, which has been of interest to scientists for several decades. Membrane bound proteins, called chemo-sensors, can sense various environmental signals and activate a signalling cascade that influences motor rotation. Together, these components comprise the chemotactic network. Recently, it has been demonstrated that the motor is not only an output of a sensory response but also a sensor itself. It can modulate its speed and direction of rotation in response to mechanical stimuli, specifically changes in the motor torque. We show that the motor is able to respond to changes in the shear flow, which is likely related to torque-sensitive mechanosensing. We are characterising this response by varying the flow speed and adjusting the availability of torque-generating stator proteins, and modifying some recent biophysical models to explore possible shear flow sensing mechanisms. These results provide insight into how E. coli navigate complex environments, but may also enable the use of the motor as a flow sensor.