Lactococcus lactis subsp. lactis boosts stress resistance and host defense mechanisms in Caenorhabditis elegans.

This article investigates the effects of Lactococcus lactis subsp. lactis strains LL100933 and LL12007 on enhancing host defense mechanisms in the nematode Caenorhabditis elegans against pathogenic infections and various stressors. Feeding C. elegans a mixture of these Lactococcus strains with Escherichia coli OP50 improved survival rates under infections by Salmonella enterica, Staphylococcus aureus, and Enterococcus faecalis, as well as under heat, UV, oxidative, and heavy metal stress, effects that were dependent on the pmk-1 (p38 MAPK) and daf-16 signaling pathways. The strains colonized the nematode gut, reduced intestinal barrier leakage during infection, and lowered reactive oxygen species levels. Transcriptomic analysis revealed upregulation of genes related to glutathione S-transferase, UDP-glucuronyl transferase, heme transport, lysozymes, and C-type lectins, suggesting enhanced innate immune and antioxidant responses. These findings highlight LL100933 and LL12007 as promising probiotics for improving host defense and stress resilience in C. elegans.