In vitro inhibitory activity of probiotic spore-forming bacilli against genotoxins

Aims: To investigate the ability of bacilli of various species (Bacillus clausii, Bacillus subtilis, Bacillus lentus, Bacillus pumilus. Bacillus megaterium, Bacillus firmus, Bacillus sp.) and origins (probiotic and collection strains) to counteract the activity of some representative DNA-reactive agents. Methods and Results: The inhibitory effect of 21 bacilli strains, previously characterized by tDNA-PCR, on four genotoxins, was examined in vitro using the short-term assay SOS-Chromotest. All strains had a high inhibitory activity against 4-nitroquinoline-1-oxide and N-methyl-N'-nitro-nitrosoguanidine (direct agents), whereas the inhibitory activity was high or moderate against 2-amino-3,4-dimethylimidazo[4,5-f]quinoline and aflatoxin B1 (indirect agents). Antigenotoxicity was observed in vegetative cells, but not heat-treated cells or spore suspensions. The spectroscopic properties of compounds were modified after cell co-incubation and all the strains maintained high viability after exposure to the genotoxins. Conclusions: No relevant differences in antigenotoxicity were evidenced among strains of the examined species or between probiotic and collection strains. Significance and Impact of the Study: Although derived from an in vitro model, the results suggest that Bacillus-based probiotics could be useful for reducing the gastrointestinal risk originating from genotoxic agents.