Xie Li, Altindal Tuba, Wu Xiao-Lun
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, United States of America.
Department of Physics, Simon Fraser University, Burnaby, BC, Canada.
PLoS One. 2015 Nov 10;10(11):e0141654. doi: 10.1371/journal.pone.0141654. eCollection 2015.
Marine bacterium Vibrio alginolyticus uses a single polar flagellum to navigate in an aqueous environment. Similar to Escherichia coli cells, the polar flagellar motor has two states; when the motor is counter-clockwise, the cell swims forward and when the motor is clockwise, the cell swims backward. V. alginolyticus also incorporates a direction randomization step at the start of the forward swimming interval by flicking its flagellum. To gain an understanding on how the polar flagellar motor switch is regulated, distributions of the forward Δf and backward Δb intervals are investigated herein. We found that the steady-state probability density functions, P(Δf) and P(Δb), of freely swimming bacteria are strongly peaked at a finite time, suggesting that the motor switch is not Poissonian. The short-time inhibition is sufficiently strong and long lasting, i.e., several hundred milliseconds for both intervals, which is readily observed and characterized. Treating motor reversal dynamics as a first-passage problem, which results from conformation fluctuations of the motor switch, we calculated P(Δf) and P(Δb) and found good agreement with the measurements.
海洋溶藻弧菌利用单一极鞭毛在水环境中导航。与大肠杆菌细胞类似,极鞭毛马达有两种状态;当马达逆时针旋转时,细胞向前游动,当马达顺时针旋转时,细胞向后游动。溶藻弧菌在向前游动间隔开始时还通过摆动其鞭毛纳入了一个方向随机化步骤。为了了解极鞭毛马达开关是如何被调节的,本文研究了向前的Δf和向后的Δb间隔的分布情况。我们发现,自由游动细菌的稳态概率密度函数P(Δf)和P(Δb)在有限时间内有强烈的峰值,这表明马达开关不是泊松分布的。短时间抑制足够强且持续时间长,即两个间隔都有几百毫秒,这很容易观察到并进行表征。将马达反转动力学视为一个首次通过问题,这是由马达开关的构象波动引起的,我们计算了P(Δf)和P(Δb),并发现与测量结果吻合良好。