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Category: Microbial Genetics and Molecular Biology
Chemotactic Signal Transduction in Escherichia coli and Salmonella typhimurium, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555818319/9781555810894_Chap06-1.gif /docserver/preview/fulltext/10.1128/9781555818319/9781555810894_Chap06-2.gifAbstract:
Bacterial chemotaxis is an important model for two-component regulatory systems. The flow of information through the chemotactic signal transduction pathway and the proteins responsible for it have been characterized in great detail. The most detailed knowledge of the chemotactic signal transduction pathway comes from studies of the closely related enteric bacteria Escherichia coli and Salmonella typhimurium. The information pathway in these species serves as the model to which all other species are usually compared. Consequently, the chapter focuses exclusively on chemotaxis in E. coli and S. typhimurium. The components of the signal pathway in these two species are virtually interchangeable. The transmembrane receptors discussed in the chapter detect compounds in the periplasm and transmit this information to the cytoplasm, but separate transport proteins are required for uptake. The chapter provides an overview of the function of components and the pathway as a whole while calling attention to some recent advances. Although chemotaxis is probably the most thoroughly understood of all signal transduction pathways, significant gaps remain in our understanding of it. Computer-based quantitative assays of chemotactic behavior are becoming available and will facilitate quantitative analysis of chemotaxis in whole free-swimming cells.
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Overall model of chemotactic signal transduction. Abbreviations: AL, CheAL; As, CheAs; B, CheB; BB, flagellar basal body; CCW, counterclockwise flagellar rotation; CW, clockwise flagellar rotation; FF, flagellar filament; FM, flagellar motor;MCP, methyl-accepting chemotaxis protein; P, phosphate; R, CheR; W, CheW; Y, CheY; Z, CheZ.
Overall model of chemotactic signal transduction. Abbreviations: AL, CheAL; As, CheAs; B, CheB; BB, flagellar basal body; CCW, counterclockwise flagellar rotation; CW, clockwise flagellar rotation; FF, flagellar filament; FM, flagellar motor;MCP, methyl-accepting chemotaxis protein; P, phosphate; R, CheR; W, CheW; Y, CheY; Z, CheZ.
Flagellar patterns during smooth swimming and tumble behaviors.
Flagellar patterns during smooth swimming and tumble behaviors.
Swimming behavior in homogeneous versus heterogeneous environments. Smooth swimming and tumbles as in Fig. 2 , with length of arrows indicating the duration of smooth swimming. Bacteria swim smoothly longer when their environment is getting better than when it is unchanging. There is no difference in smooth swimming duration between homogeneous environments and gradients when the environment is getting worse.
Swimming behavior in homogeneous versus heterogeneous environments. Smooth swimming and tumbles as in Fig. 2 , with length of arrows indicating the duration of smooth swimming. Bacteria swim smoothly longer when their environment is getting better than when it is unchanging. There is no difference in smooth swimming duration between homogeneous environments and gradients when the environment is getting worse.