Motility is important for the survival and dispersal of many bacteria, and it often plays a role during infections. Regulation of bacterial motility by chemical stimuli is well studied, but recent work has added a new dimension to the problem of motility control. The bidirectional flagellar motor of the bacterium Escherichia coli recruits or releases torque-generating units (stator units) in response to changes in load. Here, we show that this mechanosensitive remodeling of the flagellar motor is independent of direction of rotation. Remodeling rate constants in clockwise rotating motors and in counterclockwise rotating motors, measured previously, fall on the same curve if plotted against torque. Increased torque decreases the off rate of stator units from the motor, thereby increasing the number of active stator units at steady state. A simple mathematical model based on observed dynamics provides quantitative insight into the underlying molecular interactions. The torque-dependent remodeling mechanism represents a robust strategy to quickly regulate output (torque) in response to changes in demand (load).

运动性对于许多细菌的生存和传播很重要，并且通常在感染过程中发挥作用。通过化学刺激调节细菌运动已得到充分研究，但最近的工作为运动控制问题增加了一个新的维度。大肠杆菌的双向鞭毛马达响应负载的变化而招募或释放扭矩产生单元（定子单元）。在这里，我们表明鞭毛运动的这种机械敏感重塑与旋转方向无关。如果根据扭矩绘制，则先前测量的顺时针旋转电机和逆时针旋转电机的重塑速率常数落在同一曲线上。增加的扭矩降低了定子单元与电机的脱离率，从而增加了稳态下有效定子单元的数量。基于观察到的动力学的简单数学模型提供了对潜在分子相互作用的定量洞察。依赖于扭矩的重塑机制代表了一种稳健的策略，可以快速调节输出（扭矩）以响应需求（负载）的变化。