Kawagishi I, Imagawa M, Imae Y, McCarter L, Homma M
Department of Molecular Biology, Faculty of Science, Nagoya University, Japan.
Mol Microbiol. 1996 May;20(4):693-9. doi: 10.1111/j.1365-2958.1996.tb02509.x.
Certain marine Vibrio species swim in sea water, propelled by a polar flagellum, and swarm over surfaces using numerous lateral flagella. The polar and the lateral flagellar motors are powered by sodium- and proton-motive forces, respectively. The lateral flagella are produced in media of high viscosity, and the relevant viscosity sensor is the polar flagellum. The cell might monitor either the rotation rate of the flagellar motor or the mechanical force applied against the flagellum. To test these possibilities, we examined the effects of amiloride and its derivatives, which inhibit the rotation of the sodium-driven motor, on lateral flagellar gene (laf) expression in Vibrio parahaemolyticus. Phenamil, an amiloride analogue that inhibits swimming at micromolar concentrations, induced laf transcription in media devoid of viscous agents in a dose-dependent manner. The relationship between the average swimming speed and laf induction in the presence of various concentrations of phenamil was very similar to that observed when viscosity was changed. These results indicate that marine Vibrio sense a decrease in the rotation rate of (or the sodium influx through) the polar flagellar motor as a trigger for laf induction. Alternative mechanisms for laf induction are also discussed.
某些海洋弧菌借助极鞭毛在海水中游动，并利用众多侧鞭毛在表面群游。极鞭毛马达和侧鞭毛马达分别由钠动力和质子动力驱动。侧鞭毛在高粘度培养基中产生，相关的粘度传感器是极鞭毛。细胞可能监测鞭毛马达的旋转速率或作用于鞭毛的机械力。为了检验这些可能性，我们研究了氨氯吡脒及其衍生物对副溶血性弧菌侧鞭毛基因（laf）表达的影响，这些物质会抑制钠驱动马达的旋转。非那米利是一种氨氯吡脒类似物，在微摩尔浓度下就能抑制游动，它能在不含粘性剂的培养基中以剂量依赖方式诱导laf转录。在存在不同浓度非那米利的情况下，平均游动速度与laf诱导之间的关系与改变粘度时观察到的关系非常相似。这些结果表明，海洋弧菌将极鞭毛马达旋转速率的降低（或通过极鞭毛的钠内流减少）感知为laf诱导的触发因素。还讨论了laf诱导的其他机制。
