ANTIMUTAGENIC ACTION OF BACTERIA ON MUTAGENESIS INDUCED BY 4-NITROQUINOLINE-1-OXIDE IN SALMONELLA-TYPHIMURIUM

Mutagenicity of 4-nitroquinoline-1-oxide (4-NQO) with respect to Salmo nella typhimurium TA 100 was shown to decrease significantly in the pr esence of culture liquid and cells of Propionibacterium shermanii, P. pentosaceum, P. traenii, P. coccoides, P. acnes, Lactobacillus delbrue ckii, Streptococcus thermophilus, Str. faecalis, Bifidobacterium bifid um, and Escherichia coil AB 1157. The highest antimutagenic (desmutage nic) activity was found in culture liquid of all of the above strains in the logarithmic growth phase; as the cultures aged, their antimutag enic activity decreased. Cells passaged in the medium containing 4-NQO exhibited a higher antimutagenic activity than the control cells, and this phenomenon is not related to cell mutation. Young cultures of al l studied propionic acid bacteria and of Str. faecalis accumulate thio l compounds in the culture medium. Accumulation of thiols in culture l iquid of P. shermanii within a growth period between 10 and 24 h proce eded concurrently with the transition of the culture to active growth. After 24 h, the content of thiols decreased. The maximal thiol accumu lation by 24 h coincided with the maximal desmutagenic activity of the culture. It is suggested that desmutagenesis of the bacteria studied with respect to 4-NQO is associated with their production of reducing (possibly, sulfur-containing) compounds, which inactivate electrophili c groups of the mutagen.