Effect of N-carboxymethyl-N-nitrosourea on viability and mutagenic response of repair-deficient strains of Escherichia coli.

Under simulated human gastric conditions, glycocyamine which exists in meat is known to be converted into N-carboxymethyl-N-nitrosourea (CMNU) by reaction with sodium nitrite. Because of its suspected hazards to man, CMNU was tested for its mutagenicity and lethal activity with a set of isogenic strains of Escherichia coli possessing the same auxotrophic marker but different DNA-repair capacities. Both strains NG30 (recA-) and R15 (polA-) were far more sensitive to lethality induced by CMNU than H/r30R (wild) and Hs30R (uvrA-) strains. The uvrA- strain was more sensitive to induction of mutations by CMNU than the wild and polA- strains, but the recA- strain was hardly mutable by CMNU. It can be concluded from these findings that the major cause of lethality of CMNU in E. coli is different from that of mutation induction.