[Antimutagenic action of bacteria on mutagenesis induced by 4-nitroquinoline-1-oxide in Salmonella typhimurium].

It is shown that in the presence of culture liquid and cells of Propionibacterium shermanii, P. pentosaceum, P. thoenii, P. coccoides, P. acnes, Lactobacillus delbrueckii, Streptococcus thermophilus, Str. faecalis, Bifidobacterium bifidum, and Escherichia coli AB 1157 the mutagenicity of 4-nitroquinoline-1-oxide (4-NQO) in Salmonella typhimurium TA 100 decreases significantly. The highest antimutagenic (desmutagenic) activity was found in culture liquid from all strains tested in the logarithmic growth phase; on aging of the cultures their antimutagenic activity decreased. The cells passaged in the medium containing 4-NQO demonstrate a higher antimutagenic activity than the control cells, and this effect is not related to the cell mutation. Young cultures of all studied propionic bacteria and of Str. faecalis release thiol compounds into medium. Thiol accumulation in culture liquid from P. shermanii between 10 and 24 h was accompanied by culture transition to the active growth. Over 24 h thiol content decreased. The maximal thiol accumulation by 24 h coincided with the maximal desmutagenic activity of the culture. It is suggested that desmutagenesis of the bacteria studied towards 4-NQO is connected with their production of reducing (possibly, sulfur-containing) compounds that inactivate electrophilic groups of the mutagen.