N-Methyl-N'-nitro-N-nitrosoguanidine sensitivity of E. coli mutants deficient in DNA methylation and mismatch repair.

E. coli mutants deficient in DNA methylation (dam) and mismatch repair (mut) have been characterized with respect to their sensitivity to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Dam bacteria are more sensitive than mutH, mutL, and mutS single mutant bacteria. Dam mutL and dam mutS double mutant bacteria are less sensitive than dam bacteria, whereas dam mutH double mutant bacteria are as sensitive as dam bacteria. This pattern of MNNG sensitivity may be a result of the specificity of the components of the E. coli mismatch repair system.