[ODP-172] Molecular mechanism underlying resistance to S.aureus conferred by B. subtilis (natto) in C. elegans
Bacillus subtilis var. natto is a Gram-positive bacterium and used for the production of natto, a typical fermented food in Japan. The mechanisms underlying the probiotic effects are, however, largely unclear. In the present study, we investigated the influence of B. subtilis (natto) on resistance to Gram-positive and Gram-negative bacteria with using C. elegans as an alternative model host. The lifespan of the B. subtilis (natto)-fed group was significantly longer than that of the control group, upon infection to Gram-positive bacteria including Staphylococcus aureus and Enterococcus faecalis, but not to Gram-negative bacteria. B. subtilis (natto) did not increase the lifespan of skn-1/Nrf2 mutants upon infection with S. aureus. Upregulation of innate immune response-related genes by B. subtilis (natto) was dependent on skn-1/Nrf2, at least in part. The mutation in dod-24, a downstream factor of the SKN-1 pathway, partially suppressed the increase in survival time by B. subtilis (natto) upon infection with S. aureus. Cell-free supernatant of the B. subtilis (natto) have no effect on the S. aureus growth in vitro. These results suggested that B. subtilis (natto) conferred resilience to Gram-positive bacteria on the host through the SKN-1 pathway without bactericidal or bacteriostatic effects.