Acid Resistance and Stationary Phase in Escherichia coli andShigella flexneri

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9305354 Slonczewski The genetic mechanisms of resistance to extreme acid and of pH homeostasis is being investigated in Escherichia coli and its close relative Shigella flexneri. Genes have been identified which are required for stationary-phase induction of resistance to extreme acid (pH 2-3). These include katF and several Tn5 insertions of unknown location. The following questions are being addressed: What are the roles of pH and anaerobiosis is stationary-phase acid resistance? Which gene products participate in acid resistance, and how are they regulated? Do some acid-resistance loci also participate in pH homeostasis during growth? Does stationary phase also confer alkaline resistance response? The objectives are: observe pH dependence, if any, of stationary-phase acid resistance; measure pHint homeostasis and pH-dependent growth of acid-sensitive strains; screen E. coli Tn10 and lac fusion strains for acid- sensitivity, and map the loci; characterize stationary-phase alkaline resistance in E. coli. %%% pH is a major environmental parameter for bacteria, and internal pH is significant in terms of bacterial physiology and energy transduction . This research will lead to an understanding of how bacteria can survive and function in extremely acidic environments. ***