Improvement of Locomotion Caused by Lactococcus lactis subsp. lactis in the Model Organism Caenorhabditis elegans

Lactococcus lactis subsp. lactis exhibits probiotic properties in humans. Considering that Caenorhabditis elegans can be used to study the effects of microorganisms on animal behavior, owing to its simple nervous system, we assessed the impacts of two strains of Lactococcus lactis subsp. Lactis—a non-nisin-producing strain, NBRC 100933 (LL100933), and a nisin-producing strain, NBRC 12007 (LL12007)—on the lifespan, locomotion, reproductive capacity of, and lipid accumulation in, C. elegans. The lifespan of adult C. elegans fed a mixture (1:1) of Escherichia coli OP50 and LL100933 or LL12007 did not show a significant increase compared to that of the group fed a standard diet of E. coli OP50. However, the nematodes fed Lactococcus strains showed notable enhancement in their locomotion at all of the tested ages. Further, the beneficial effects of LL100933 and LL12007 were observed in the daf-16 mutants, but not in the skn-1 and pmk-1 mutants. The lipid accumulation in the worms of the Lactococcus-fed group was lower than that in the control group at all experimental ages. Overall, LL100933 and LL12007 enhance the locomotor behavior of C. elegans, likely by modulating the PMK-1/p38 MAPK and SKN-1/Nrf2 transcription factors.