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）。该系统的生物化学和生理学研究正在用大肠杆菌和一种活动链球菌进行。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被人工激活。无论是用游动的细胞还是用鞭毛系在玻璃上的细胞，都已经对质子动势、质子通量、扭矩和速度进行了测量。已分离并鉴定了产生转矩元件MotA和MotB的突变体。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。运动是生物的一种重要现象。在细菌的世界里，鞭毛介导的游动运动允许对化学或物理刺激（如营养物质、光线、屏障）做出反应，这对于缓解群体过度拥挤、个体细菌的维持和遗传交配是必要的。细菌的鞭毛和它的马达很小，但很有效。除了提供对生物行为的分子基础的理解之外，这项研究的结果还可以在纳米制造或生物材料研究中找到用途（例如，使用天然或人工鞭毛作为开关）。

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 energize artificially. Measurements have been made, either with swimming cells or with cells tethered to glass by a flagellum, of protonmotive force, proton flux, torque and speed. Mutants of the torque-generating elements MotA and MotB have been isolated and characterized. This work has 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. %%% Motility is a critical phenomenon of living things. In the world of bacteria, flagellum-mediated swimming movement allows for responses to chemical or physical stimuli (such as nutrients, light, barriers) which are necessary for alleviating colonial overcrowding, sustenance of individual bacteria, and genetic mating. The bacterial flagellum and its motor are tiny, yet effective. In addition to providing an understanding of the molecular basis for biological behavior, the results of this research could find usefulness in nanofabrication or biomaterials research (e.g., using natural or artificial flagella as switches).