[Differences in the mutagenic effectiveness of N-nitrosomethyl- and N-nitrosoethylurea acting on bacterial DNA in vivo].

Chemically induced lethals and reversion frequencies of two mutants of Salmonella typhimurium LT-2 1530 and 1532 were examined. Prototrophic mutants to histidine independence occurred by two different mechanisms and were induced by nitrous acid, hydroxylamine, N-nitrosomethylurea (NMU), N-nitrosoethylurea (NEU) and N, N, nitrosodimethylurea (NDMU). The ability of the mutants to revert was affected by the chemical structure (in the row of N-nitrosoalkylurea - by alkyl group) of the mutagen. NEU is found to induce in bacterial DNA only base pair substitutions; NMU and NDMU - deletions and base pair substitutions. An original model of deletion mechanism with Goldwait endonuclease II participation is proposed.