Lapidus I R, Welch M, Eisenbach M
Department of Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel.
J Bacteriol. 1988 Aug;170(8):3627-32. doi: 10.1128/jb.170.8.3627-3632.1988.
When bacterial cells are tethered to glass by their flagella, many of them spin. On the basis of experiments with tethered cells it has generally been thought that the motor which drives the flagellum is a two-state device, existing in either a counterclockwise or a clockwise state. Here we show that a third state of the motor is that of pausing, the duration and frequency of which are affected by chemotactic stimuli. We have recorded on video tape the rotation of tethered Escherichia coli and Salmonella typhimurium cells and analyzed the recordings frame by frame and in slow motion. Most wild-type cells paused intermittently. The addition of repellents caused an increase in the frequency and duration of the pauses. The addition of attractants sharply reduced the number of pauses. A chemotaxis mutant which lacks a large part of the chemotaxis machinery owing to a deletion of the genes from cheA to cheZ did not pause at all and did not respond to repellents by pausing. A tumbly mutant of S. typhimurium responded to repellents by smooth swimming and to attractants by tumbling. When tethered, these cells exhibited a normal rotational response but an inverse pausing response to chemotactic stimuli: the frequency of pauses decreased in response to repellents and increased in response to attractants. It is suggested that (i) pausing is an integral part of bacterial motility and chemotaxis, (ii) pausing is independent of the direction of flagellar rotation, and (iii) pausing may be one of the causes of tumbling.
当细菌细胞通过鞭毛附着在玻璃上时，许多细胞会旋转。基于对附着细胞的实验，人们普遍认为驱动鞭毛的马达是一种双态装置，存在于逆时针或顺时针状态。在这里，我们表明马达的第三种状态是暂停状态，其持续时间和频率受趋化刺激的影响。我们用录像带记录了附着的大肠杆菌和鼠伤寒沙门氏菌细胞的旋转，并逐帧和慢动作分析了记录。大多数野生型细胞会间歇性地暂停。添加驱避剂会导致暂停的频率和持续时间增加。添加引诱剂会大幅减少暂停的次数。由于从cheA到cheZ基因的缺失而缺少大部分趋化机制的趋化突变体根本不会暂停，也不会通过暂停对驱避剂做出反应。鼠伤寒沙门氏菌的一个翻滚突变体通过平滑游动对驱避剂做出反应，通过翻滚对引诱剂做出反应。当附着时，这些细胞表现出正常的旋转反应，但对趋化刺激有相反的暂停反应：暂停频率在对驱避剂的反应中降低，在对引诱剂的反应中增加。有人提出：（i）暂停是细菌运动性和趋化性的一个组成部分；（ii）暂停与鞭毛旋转方向无关；（iii）暂停可能是翻滚的原因之一。
