[Mutagenic effect of oxidizing agents on the thermally-induced prophage lambda cI857: effect of a system of oxidative stress].

The lethal and mutagenic effects of hydrogen peroxide H2O (2-20 mM), cumene hydroperoxide (0.2-2.0 mM), and potassium permanganate KMnO4 (0.25-1.0 mM) on the heat-inducible lambda cI857 prophage were studied under conditions of heat-induction immediately after the mutagenic treatment of lysogenic cells of Escherichia coli oxyR+ or oxyR delta 3. Within the range of the doses used, these agents decreased prophage survival by 3-5 orders of magnitude and increased mutation frequency by up to 0.2% under the action of hydrogen peroxide and cumene hydroperoxide, and up to 1.5% in the case of KMnO4 (in oxyR+ cells). In the absence of the inducible OxyR system of oxidative stress, both lethal and mutagenic effects of H2O were enhanced. The oxyR delta 3 mutation increased lethal and mutagenic effects of cumene hydroperoxide and KMnO4 only at the highest concentrations used. Apparently, the OxyR system does not repair lesions induced by oxidative agents, but only prevents their formation.