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 f or oxidatively damaged DNA in Escherichia coli cells. Peroxide stress was brought about by adding 30 mu M hydrogen peroxide (H2O2) to expone ntially growing cells. The following results were obtained. (1) After exposure to H2O2, E coli resistance to X-rays was enhanced. The acquis ition 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 cel ls 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(+)-media ted regulatory system.