The effects of mutations in the polA and recA genes on mutagenesis by nitrosoguanidine in Salmonella typhimurium.

Results of semi-quantitative plate tests indicated that polA and recA mutants of Salmonella typhimurium strain LT2 trpB1 might be significantly less mutable by nitrosoguanidine (MNNG) than were their repair-proficient parents strains. Quantitative data obtained in treat-and-plate experiments showed that this was not the case, at least for low doses of MNNG, and also that the recA strain was significantly more mutable at low doses than its Rec+ parent. On the basis of these results it is suggested that cells of S. typhimurium may possess a recA+-dependent repair pathway capable of error-free removal of MNNG-induced pre-mutational lesions from their DNA.