Repair replication in different strains of Escherichia coli after treatment with alkylating agents and its dependence on protein synthesis

Abstract

1. The effect of mitomycin C or nitrogen mustard in Escherichia coli K 12 strains T71 arg − and AB2463 (rec −) under conditions where the cellular DNA remains constant has been studied. 2. After exposure of T71 arg − and AB2463 to mitomycin C (10 μg/ml) or nitrogen mustard (300 μg/ml), an incorporation of labelled thymidine into DNA (no increase in cellular DNA) corresponding to about 20 % that in control culture was found in T71 arg −. No incorporation took place in the case of AB2463. 3. No incorporation of [ Me- 3H] thymidine took place into the cellular DNA of the T71 arg − when arginine was absent or chloramphenicol was added during exposure to mitomycin C or nitrogen mustard. The results could be interpreted to mean that repair replication after treatment with alkylating agents is dependent on protein synthesis. 4. When T71 arg − and AB2463 were prelabelled with [ Me- 3H]thymidine, a decrease with time in the total radioactivity of cellular DNA was found after exposure to mitomycin C. The degradation of DNA was not dependent on protein synthesis.