title: Mutation and DNA replication in Escherichia coli treated with low concentrations of N-methyl-N'-nitro-N-nitrosoguanidine.
abstract: N-Methyl-N'-nitro-N-nitrosoguanidine (nitrosoguanidine) causes an unexpectedly high frequency of closely linked double mutants because of its specificity for chromosome regions in replication. Low nitrosoguanidine concentrations (I mug/ml) in liquid cultures allow replications at the normal rate and are mutagenic. It was expected that mutations would be spread over the chromosome as it replicated, but a high frequency of closely linked double mutants was found. If a thymine auxotroph is grown in the presence of 5-bromodeoxyuridine (BUdR) and nitrosoguanidine, then exposed to 313-nm radiation (which destroys BUdR-substituted DNA), the mutation frequency is much higher among survivors than among non-irradiated cells. It is concluded that nitrosoguanidine inhibits DNA replication in a small fraction of the population and that mutations are induced in that same fraction. Nitrosoguanidine treatment leads to a high frequency of closely linked double mutants under all known conditions.
mesh_terms: D001120:Arginine; D001973:Bromodeoxyuridine; D002250:Carbon Radioisotopes; D002470:Cell Survival; D004261:DNA Replication / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D005799:Genes, Dominant; D007930:Leucine; D008769:Methylnitronitrosoguanidine / Q000378:metabolism / Q000494:pharmacology*; D009153:Mutagens; D009154:Mutation / Q000187:drug effects*; D009604:Nitrosoguanidines / Q000494:pharmacology*; D013307:Streptomycin / Q000494:pharmacology; D013936:Thymidine; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D002250:Carbon Radioisotopes; D009153:Mutagens; D009604:Nitrosoguanidines; D008769:Methylnitronitrosoguanidine; D001120:Arginine; D001973:Bromodeoxyuridine; D007930:Leucine; D013936:Thymidine; D013307:Streptomycin