Induction of repair capacity for oxidatively damaged DNA as a component of peroxide stress response in Escherichia coli.

We examined whether or not peroxide stress induces a repair capacity for oxidatively damaged DNA in Escherichia coli cells. Peroxide stress was brought about by adding 30 microM hydrogen peroxide (H2O2) to exponentially growing cells. The following results were obtained. (1) After exposure to H2O2, E. coli resistance to X-rays was enhanced. The acquisition of resistance was inhibited by rifampicin and chloramphenicol. (2) The response was acquired in mutants defective in the katG and oxyR genes, as well as in the wild-type strain. (3) Lambda phages damaged by exposure to H2O2 showed higher survival on H2O2-treated cells than on untreated cells. (4) The peroxide stress did not render E. coli cells resistant to UV and mitomycin C. These suggest that peroxide stress induces a repair capacity against oxidative DNA damage and that this response must be regulated by a different mechanism from oxyR(+)-mediated regulatory system.