Properties of an L-glutamate-induced acid tolerance response which involves the functioning of extracellular induction components
1999
Rowbury, R.J. | Humphrey, T.J. | Goodson, M.
Escherichia coli became more acid tolerant following incubation for 60 min in a medium containing L-glutamate at pH 7(.)0, 7(.)5 or 8(.)5. Several agents, including NaCl, sucrose, SDS and DOC, prevented tolerance appearing if present with L-glutamate. Lesions in cysB, hns, fur, himA and relA, which frequently affect pH responses, failed to prevent L-glutamate-induced acid tolerance but a lesion in L-glutamate decarboxylase abolished the response. Induction of acid tolerance by L-glutamate was associated with the accumulation in the growth medium of a protein (or proteins) which was able to convert pH 7(.)0-grown cultures to acid tolerance, and the original L-glutamate-induced tolerance response was dependent on this component(s). Acid tolerance was also induced by L-aspartate at pH 7(.)0 and induction of such tolerance was dependent on an extracellular protein (or proteins). The L-glutamate and L-aspartate acid tolerance induction processes are further examples of a number of stress tolerance responses which differ from most inductions in that extracellular components, including extracellular sensors, are required.
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