Physiological role of RpoS-controlled functions of Escherichia coli

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Increasing our knowledge regarding bacterial genes that are expressed in response to nutrient deprivation or other stresses is crucial for understanding basic aspects of bacterial physiology and environmental adaptation. In recent years, much has been learned about a key conserved regulator, RpoS, that is required for the expression of a large number of stress-induced genes but many unanswered questions remain. We do not have a full understanding of the function of genes controlled by RpoS. To address this, we will use genetic and molecular biology tools to examine the expression of RpoS-dependent genes that we have isolated. By simultaneously characterizing many RpoS-dependent genes, we will learn how these genes differ as a class from so-called housekeeping genes that are required for normal growth. In addition to characterizing RpoS-dependent genes, we will investigate specific questions that have arisen from our previous studies regarding lysine decarboxylase, transaldolase and catalase expression. Each of these stationary-specific genes are probably important in helping the cell adapt to stress conditions since we have found that they are expressed only in stationary phase when cells are in a starved state--they are not expressed under normal conditions. We will also examine how selected mutations in RpoS contribute to the overall fitness of the bacterial cell and will use metabolite analysis to discover how RpoS affects metabolite flux in bacteria maintained under suboptimal growth conditions. These studies will extend our knowledge of factors that contribute to bacterial persistence and survival.