Bacterial Flagellar Rotation

细菌鞭毛在其底部由旋转马达驱动，该马达包括嵌入细胞壁和细胞膜的杆和一组环。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，偏向取决于感觉传导，例如，细胞对化学刺激(趋化性)的反应。对这一系统的生化和生理学的研究正在用大肠杆菌和一种可移动的链球菌进行。使用E.Coli是因为它的马达结构可以被遗传干扰；使用链球菌是因为它的马达可以被人工充电。无论是用游动的细胞还是用鞭毛拴在玻璃上的细胞，都已经进行了质子动势、质子通量、扭矩和速度的测量。扭矩产生元件MOTA和MOTB的突变体已经被分离和鉴定。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，正在接受进一步的测试。我们的目标是在分子水平上理解鞭毛的旋转，或者更广泛地说，理解生物如何利用化学能来做机械功。运动是生物的一种临界现象。在细菌世界中，鞭毛介导的游泳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，这些刺激对于缓解群体过度拥挤、单个细菌的生存和遗传交配是必要的。细菌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处(例如，使用天然或人造鞭毛作为开关)。

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).