Locsei J T
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, UK.
J Math Biol. 2007 Jul;55(1):41-60. doi: 10.1007/s00285-007-0080-z. Epub 2007 Mar 13.
Escherichia coli is a motile bacterium that moves up a chemoattractant gradient by performing a biased random walk composed of alternating runs and tumbles. Previous models of run and tumble chemotaxis neglect one or more features of the motion, namely (a) a cell cannot directly detect a chemoattractant gradient but rather makes temporal comparisons of chemoattractant concentration, (b) rather than being entirely random, tumbles exhibit persistence of direction, meaning that the new direction after a tumble is more likely to be in the forward hemisphere, and (c) rotational Brownian motion makes it impossible for an E. coli cell to swim in a straight line during a run. This paper presents an analytic calculation of the chemotactic drift velocity taking account of (a), (b) and (c), for weak chemotaxis. The analytic results are verified by Monte Carlo simulation. The results reveal a synergy between temporal comparisons and persistence that enhances the drift velocity, while rotational Brownian motion reduces the drift velocity.
大肠杆菌是一种能运动的细菌，它通过执行由交替的游动和翻滚组成的有偏随机游动，沿着化学引诱剂梯度向上移动。先前的游动和翻滚趋化模型忽略了运动的一个或多个特征，即：(a) 细胞不能直接检测化学引诱剂梯度，而是对化学引诱剂浓度进行时间比较；(b) 翻滚并非完全随机，而是表现出方向持续性，这意味着翻滚后的新方向更有可能在前半球；(c) 旋转布朗运动使大肠杆菌细胞在游动过程中无法沿直线游动。本文针对弱趋化作用，考虑了(a)、(b)和(c)，给出了趋化漂移速度的解析计算。解析结果通过蒙特卡罗模拟得到验证。结果揭示了时间比较和持续性之间的协同作用增强了漂移速度，而旋转布朗运动降低了漂移速度。
