Cells of Propionibacterium freudenreichii subsp shermanii lower the mutagenicity of 4nitroquinoline-1-oxide in the tester strain Salmonella typhimurium TA 100 in the modified Ames test. The bacterial adaptation to the mutagen presence in the medium is demonstrated. It is possibly Iinked to induction of an antimutagenic activity. A dialysed fraction of soluble proteins of the extract (dialysate) lowers the mutagenicity of UV-C light in Salmonella typhimurium and manifests protective and

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... ive effects on UV-B-and UV-C-irradiated cells of S typhimurium, Escherichia coli and the yeast Candida guilliermondii. The reactivation does not occur alter the cell irradiation with a light of total optical spectrum and visible light. (The last was studied with the yeasts.) These data serve as an indirect indication of the dialysate proteins participation in the repair of DNA injured by UV-B and UV-C irradiation. The reactivation by dialysate occurs in E coli and the yeasts Saccharomyces cerevisiae and C guilliermondii, inactivated by heating. The reactivative activity of the dialysate was localized in its 2 subfractions that manifests in E coli inactivated not only by UV light but also by heating.