Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui, China.
School of Biological and Medical Engineering, Hefei University of Technology, Hefei, Anhui, China.
Biophys J. 2018 Dec 4;115(11):2242-2249. doi: 10.1016/j.bpj.2018.10.020. Epub 2018 Oct 30.
Bacteria can use the second messenger c-di-GMP to adjust their motility in response to environmental cues. The protein YcgR, upon binding of c-di-GMP, interacts with the flagellar motor to affect the motor behavior. However, the full feature of the effects of c-di-GMP::YcgR on the flagellar motor remains unclear, and its interacting partners on the motor is still controversial. Here, we characterized the effects of c-di-GMP::YcgR on the torque-speed curve of the flagellar motor, one of the most important properties of the motor, finding that it affects the motor behavior throughout the full range of load conditions from zero to high loads by shifting the motor torque-speed curve downward. We also investigated the interacting partner on the motor through dynamical fluorescent studies, finding that c-di-GMP::YcgR mainly interacts with the motor-switch complex instead of the torque-generating units (stators). To directly test the behavioral consequence of elevated c-di-GMP levels, we measured the distribution of bacteria swimming near a surface, finding that elevated c-di-GMP levels promote bacterial aggregation on surfaces. The effects of c-di-GMP on bacterial motile behavior that we characterized here are consistent with the key role that c-di-GMP plays in the transition between motile and sedentary forms of bacterial life.
细菌可以利用第二信使 c-di-GMP 来调节其运动性，以响应环境线索。当结合 c-di-GMP 时，蛋白质 YcgR 与鞭毛马达相互作用，从而影响马达行为。然而，c-di-GMP::YcgR 对鞭毛马达的影响的全部特征仍然不清楚，其在马达上的相互作用伙伴仍然存在争议。在这里，我们表征了 c-di-GMP::YcgR 对鞭毛马达的转矩-速度曲线的影响，转矩-速度曲线是马达最重要的特性之一，结果发现它通过向下移动马达的转矩-速度曲线来影响整个从零到高负载的全负载范围内的马达行为。我们还通过动态荧光研究调查了马达上的相互作用伙伴，发现 c-di-GMP::YcgR 主要与马达开关复合物相互作用，而不是与产生扭矩的部件（定子）相互作用。为了直接测试 c-di-GMP 水平升高的行为后果，我们测量了在表面附近游动的细菌的分布，发现 c-di-GMP 水平的升高促进了细菌在表面上的聚集。我们在这里描述的 c-di-GMP 对细菌运动行为的影响与 c-di-GMP 在细菌游动和静止生活形式之间的转变中所起的关键作用是一致的。
