SENSORY TRANSDUCTION IN BACTERIAL CHEMOTAXIS

能动细菌具有刺激-反应系统，其中输入是 引诱剂或驱避剂的局部浓度，输出是 细胞的运动。 已知一些化学品，例如，糖和 氨基酸，被特定的受体感知， 占据导致鞭毛旋转偏置的变化（概率 鞭毛逆时针旋转），但是 受体与鞭毛的偶联仍然不清楚。 我们将继续 我们对这个系统的生理学研究， 大肠杆菌栓系细胞在台阶和冲击下的行为 刺激。 从基因工程菌株的反应， 修饰的tar（天冬氨酸受体）和tsr（丝氨酸受体）蛋白，我们 希望了解有关受体占有率的信息如何通过 细胞质膜以及不同受体类别如何相互作用。 从 鞭毛标记物对不同浓度刺激的丝状细胞的反应 点沿着他们的长度，我们将确定的物理性质， 将信息从感受器传递到鞭毛的物质。 我们 应该能够确定它的扩散系数和大小。 通过 跟踪和拴系来自同一培养物的细胞， 游泳和旋转行为，我们希望了解更多关于 同一细胞内不同鞭毛的同步化。 这项工作 补充了在其他领域开展的遗传学和生物化学方面的工作， laboratories. 长期目标是在分子水平上理解 参与受体功能和感觉的基本过程的水平 转导

Motile bacteria possess a stimulus-response system in which the input is the local concentration of an attractant or repellent and the output is the motion of the cell. It is known that some chemicals, e.g., sugars and amino acids, are sensed by specific receptors and that changes in receptor occupancy lead to changes in flagellar rotational bias (the probability that the flagella spin counterclockwise), but the way in which the receptors are coupled to the flagella remains obscure. We will continue our studies of the physiology of this system by examining the rotational behavior of tethered cells of Escherichia coli exposed to step and impulse stimuli. From responses of genetically engineered strains containing modified tar (aspartate receptor) and tsr (serine receptor) proteins, we expect to learn how information about receptor occupancy crosses the cytoplasmic membrane and how different receptor classes interact. From the responses of flagellar markers on filamentous cells stimulated at different points along their length, we will determine the physical properties of the substance that carries information from the receptors to the flagella. We should be able to determine its diffusion coefficient and its size. By tracking and tethering cells from the same culture and comparing their swimming and rotational behavior, we expect to learn more about synchronization of different flagella in the same cell. This work complements that on genetics and biochemistry pursued in other laboratories. The long-range goal is an understanding at the molecular level of basic processes involved in receptor function and sensory transduction.