Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138;
Rowland Institute at Harvard, Harvard University, Cambridge, MA 02142.
Proc Natl Acad Sci U S A. 2021 Apr 13;118(15). doi: 10.1073/pnas.2024608118.
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 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扩散很重要，而且它通常在感染过程中发挥作用。化学刺激物对细菌运动性的调节已得到充分研究，但最近的研究工作为运动性控制问题增添了新的维度。细菌的双向鞭毛马达会根据负载的变化招募或释放产生扭矩的单元（定子单元）。在这里，我们表明，这种鞭毛马达的机械敏感性重塑与旋转方向无关。如果根据扭矩绘制先前测量的顺时针旋转马达和逆时针旋转马达的重塑率常数，则它们落在同一条曲线上。增加的扭矩会降低定子单元从马达中脱离的速度，从而在稳定状态下增加了活跃的定子单元的数量。基于观察到的动力学的简单数学模型提供了对基础分子相互作用的定量见解。这种依赖于扭矩的重塑机制代表了一种快速响应需求（负载）变化而调节输出（扭矩）的稳健策略。
