Properties of an L-glutamate-induced acid tolerance response which involves the functioning of extracellular induction components

Escheichia coli became more acid tolerant following incubation for 60 min i n a medium containing L-glutamate at pH 7.0, 7.5 or 8.5. Several agents, in cluding cAMP, NaCl, sucrose, SDS and DOG, prevented tolerance appearing if present with L-glutamate. Lesions in cysB, hns, fur, himA and relA, which f requently affect pH responses, failed to prevent L-glutamate-induced acid t olerance but a lesion in L-glutamate decarboxylase abolished the response. Induction of acid tolerance by L-glutamate was associated with the accumula tion in the growth medium of a protein (or proteins) which was able to conv ert pH 7.0-grown cultures to acid tolerance, and the original L-glutamate-i nduced tolerance response was dependent on this component(s). Acid toleranc e 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 a nd 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 require d.