Acid sensitivity induction (ASI) at alkaline pH in Escherichia coli involves two major sensitization components, induction of both being switched on by increased internal pH |
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| Authors: | R J Rowbury Margaret Goodson T J Humphrey |
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| Institution: | Biology Department (Darwin), University College London, Gower Street, London WC1E 6BT, UK;*Public Health Laboratory, Church Lane, Heavitree, Exeter EX2 5AD, UK |
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| Abstract: | Acid sensitivity induction (ASI) at alkaline pH in Escherichia coli 1157 ( phoE ) is only fully mounted if protein synthesis occurs for the first 5 min of the 12–15 min induction period, but appreciable sensitization occurs in the presence of chloramphenicol indicating that there are protein synthesis-independent and -dependent components (components 1 and 2). Component 1 sensitization is in place after 10 min at pHo 9.0 but the dependent process is induced slightly more slowly. Collapsing ΔpH at pHo 9.0 did not prevent full ASI, indicating that component 1 and 2 induction does not depend on increased ΔpH. The two induction (or activation) processes responded differently to intermediate levels of external alkalinization; component 1 was induced at pHo 8.3 but component 2 needed pHo 8.4 or greater. Collapsing ΔpH at pHo 8.0 led to full induction of component 1 and appreciable induction of component 2, indicating that both processes are triggered if pHi rises to 8.0 or greater (presumably at pHo 8.3–8.4). Component 1 appears less important for ASI in 1157-4 ( phoE +) than in 1157 ( phoE ). |
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