The study of induced antimutagenesis of propionic acid bacteria

Abstract

Using the modified Ames test it was shown that Propionibacterium shermanii (a classical propionic bacterium) excretes substances lowering 4-nitroquinoline-1-oxide (4NQO) and UV-induced mutagenesis in Salmonella typhimurium TA 100. Reconstruction experiments showed that antimutagenic properties of a cultural broth and cell dialysate are not caused by inhibition of S. typhimurium cell growth. By passing the propionic acid bacteria through a medium containing small amounts of 4NQO, induced antimutagenesis was demonstrated. Induced P. shermanii cells differ from control in having a higher level of antimutagenicity against 4NQO-induced mutagenesis, and a higher GSH transferase activity and do not differ in content of sulfhydryl compounds. Experiments with cell dialysates showed that the induction of the antimutagenesis against 4NQO is accompanied by enhancing antimutagenicity against UV-irradiation. In the model experiments it was shown that the cell dialysates, possessing GSH transferase activity, accelerate a reaction between GSH and 4NQO, but do not influence the 4NQO inactivation by some components of the cultural broth. We suggest that the mechanism of inhibition of electrophilic mutagens in the cells is connected with GSH-GSH transferase system though the inhibitory mechanism of cultural broth may be different.