SENSORY TRANSDUCTION IN BACTERIA

大多数细菌趋化性途径涉及 感觉转换器。 本实验室的研究涉及 鼠伤寒沙门氏菌中甲基化非依赖性途径和 趋氧性（趋气性）和趋糖性大肠杆菌 通过磷酸转移酶系统（PTS）转运。 的 甲基化非依赖性和甲基化依赖性途径汇合 在开关之前-用于控制 鞭毛马达。 我们的目标是在分子层面上详细描述信号 这些行为的处理机制。 临时技术秘书处的趋同 系统和主要的趋化途径将使用遗传 用纯化的蛋白质对系统进行分析和重构。 一 将开发用于趋化性的灵敏分光光度测定法 用于复溶研究。 具有趋气性缺陷的突变体 将被选择和表征，突变图谱和基因 克隆的。 与趋气性基因产物相互作用的组分将被 通过等位基因特异性抑制分析鉴定。 拟议 将通过用纯化组分复溶来证实机制。 E. coli和革兰氏阳性菌S.鼠伤寒被高浓度 氧气浓度。 反应的生理学将 研究，包括抑制或诱导，对氧的需求 消耗或氧化还原传感和避氧的可加性 反应和趋化反应。 遗传和生化 将使用与上述类似的研究来确定 回避反应的组成部分和与 趋化性途径。 活性氧或ApppppA的可能作用 在介导应答中的作用将被研究。 趋气性 盐生盐杆菌是唯一的趋氧性 甲基化依赖性，我们将进一步研究 这个回应。

Most pathways for bacterial chemotaxis involve methylation of the sensory transducer. Studies in this laboratory are concerned with methylation-independent pathways in Salmonella typhimurium and Escherichia coli for chemotaxis to oxygen (aerotaxis) and to sugars transported by the phosphotransferase system (PTS). The methylation-independent and the methylation-dependent pathways converge before the switch -that controls the direction of rotation of the flagellar motors. The goal is to describe in molecular detail the signal processing mechanisms in these behaviors. The convergence of the PTS system and the main chemotaxis pathway will be investigated using genetic analysis and reconstitution of the system with purified proteins. A sensitive spectro-photometric assay for chemotaxis will be developed for use in the reconstitution studies. Mutants with a defect in aerotaxis will be selected and characterized, the mutation mapped and the gene cloned. Components interacting with the aerotaxis gene product will be identified by allele-specific suppression analysis. The proposed mechanism will be confirmed by reconstitution with purified components. E. coli and S. typhimurium are repelled by high concentrations of oxygen. The physiology of the response will be investigated, including repression or induction, a requirement for oxygen consumption or redox sensing and the additivity of the oxygen-avoidance response and chemotactic responses. Genetic and biochemical investigations similar to those described above will be used to determine components of the avoidance response and the site of convergence with the chemotaxis pathway. A possible role of reactive oxygen species or AppppA in mediating the response will be investigated. Aerotaxis in Halobacterium halobium is the only aerotaxis that is methylation-dependent and we will further investigate the mechanism of this response.