Induction of the alkylation-inducible aidB gene of Escherichia coli by cytoplasmic acidification and N-ethylmaleimide.

We have studied the effects of changes in intracellular pH and the influence of thiol reagents on the induction of the DNA damage-inducible genes of Escherichia coli, aidB, alkA, and alkB. Under aerobic conditions in the absence of alkylating agents aidB, but not alkA or alkB, was induced by an acidification of cytoplasm or by treatment with the sulfhydryl reagent N-ethylmaleimide. Alkaline shift and thiosalicyclic acid did not affect the induction of aidB and alkB. The induction of alkA increased under the alkaline shift but not in the case of treatment with reducing agents. Compared with the aidB gene, a component of the SOS system, the sulA (sfiA) gene, responded to changes in cytoplasmic pH and in the level of intracellular thiols in an opposite way. SulA induction was observed under alkaline shift and after treatment with thiosalicylic acid.