Bacterial Flagellar Rotation

细菌的鞭毛是由嵌入细胞壁和细胞质膜中的一根杆和一组环组成的旋转马达在其基部驱动的。旋转的能量由电化学质子梯度提供。马达交替顺时针和逆时针旋转，根据感觉转导，例如，根据细胞对化学刺激的反应（趋化性）。目前正在利用大肠杆菌和一种活动链球菌对该系统进行生物化学和生理学研究。之所以使用大肠杆菌，是因为它的马达结构可以被基因干扰。链球菌之所以被使用，是因为它的马达可以人工激活。已经对游动细胞或通过鞭毛系在玻璃上的细胞，或质子动势、质子通量、扭矩和速度进行了测量。瘫痪突变体是由携带在质粒上的基因编码的野生型蛋白合成来修复的。这项工作已经产生了一个与现有实验数据一致的电机模型，该模型正在接受进一步的测试。目标是在分子水平上理解鞭毛旋转，或者更广泛地说，理解生物是如何利用化学能做机械功的。

A bacterial flagellum is driven at its base by a rotary motor comprising a rod and set of rings embedded in the cell wall and cytoplasmic membrane. The energy for rotation is supplied by an electrochemical proton gradient. The motor spins alternately clockwise and counterclockwise, with a bias depending on sensory transduction, for example, on the cell's response to chemical stimuli (chemotaxis). Studies of the biochemistry and physiology of this system are being made with Escherichia coli and a motile streptococcus. E. coli is being used, because the structure of its motors can be perturbed genetically. Streptococcus is being used, because its motors can be energized artificially. Measurements have been made, either with swimming cells or with cells tethered to glass by a flagellum, or protonmotive force, proton flux, torque and speed. Paralyzed mutants have been repaired by synthesis of wild-type protein encoded by genes carried on plasmids. This work had led to a model for the motor consistent with existing experimental data that is being subjected to further test. The goal is an understanding of flagellar rotation at the molecular level, or more broadly, of how living things use chemical energy to do mechanical work.