首页 | 本学科首页   官方微博 | 高级检索  
     


Direct observation of speed fluctuations of flagellar motor rotation at extremely low load close to zero
Authors:Shuichi Nakamura  Yuta Hanaizumi  Yusuke V. Morimoto  Yumi Inoue  Marc Erhardt  Tohru Minamino  Keiichi Namba
Affiliation:1. Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai, Japan;2. Faculty of Computer Science and Systems Engineering, Department of Physics and Information Technology, Kyushu Institute of Technology, Fukuoka, Japan;3. Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan;4. Institut für Biologie/Bakterienphysiologie, Humboldt-Universität zu Berlin, Berlin, Germany
Abstract:The bacterial flagellar motor accommodates ten stator units around the rotor to produce large torque at high load. But when external load is low, some previous studies showed that a single stator unit can spin the rotor at the maximum speed, suggesting that the maximum speed does not depend on the number of active stator units, whereas others reported that the speed is also dependent on the stator number. To clarify these two controversial observations, much more precise measurements of motor rotation would be required at external load as close to zero as possible. Here, we constructed a Salmonella filament-less mutant that produces a rigid, straight, twice longer hook to efficiently label a 60 nm gold particle and analyzed flagellar motor dynamics at low load close to zero. The maximum motor speed was about 400 Hz. Large speed fluctuations and long pausing events were frequently observed, and they were suppressed by either over-expression of the MotAB stator complex or increase in the external load, suggesting that the number of active stator units in the motor largely fluctuates near zero load. We conclude that the lifetime of the active stator unit becomes much shorter when the motor operates near zero load.
Keywords:bacterial flagellar motor  duty ratio  hook  MotAB stator complex  torque generation
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号