RUI: pH Regulation of Genes in Escherichia coli

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The genetic response to pH change will be investigated in Escherichia coli. External pH is a major environmental parameter for bacteria, and internal pH is significant in terms of bacterial physiology and energy transduction. Two novel pH- regulated loci, isolated as lacZ operon fusions, will be studied: ina inducible by membrane-permeable weak acids and protonophores, and alx inducible by external base. These loci will be cloned and sequenced, and their sequences analyzed for promoters and regulatory sites. The possible regulatory role of acid-sensitive sequences such as H-DNA will be investigated. The pH dependence of ina transcription will be tested in vitro. Regulator genes for ina and alx will be isolated, by screening Tn10 pools for isolates which are either constitutive or uninducible. Mutants exhibiting defective pH homeostasis will be sought.