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

Aims: To investigate the effects of Lactococcus lactis subsp. lactis strains LL100933 and LL12007 on the host defense mechanisms of Caenorhabditis elegans against pathogenic infections and stressors.

Methods And Results: Caenorhabditis elegans fed a 1:1 mixture of Escherichia coli OP50 and LL100933 (OP50 + LL100933) or E. coli OP50 and LL12007 (OP50 + LL12007) had significantly higher survivability than the control diet (OP50). Moreover, when OP50 + LL100933 and OP50 + LL12007 were fed to C. elegans deficient in daf-16 and pmk-1, survival did not exceed that of control-fed worms under Salmonella infection. Therefore, these strains may enhance the survivability of C. elegans through the p38 MAPK and DAF-16-related pathways. Gene expressions responsible for these enhanced defense responses were estimated using RNA sequencing and gene ontology analysis. The test groups showed significant upregulation of glutathione S-transferase (gsto-1, gst-5, and gst-17), UDP-glucuronyl transferase (ugt-13, ugt-16, and ugt-21), heme-responsive (hrg-4), invertebrate-type lysozyme (ilys-2), and C-type lectin (clec-52) genes compared to those in the control group.

Conclusion: Lactococcus lactis subsp. lactis LL100933 and LL12007 strains demonstrated promising benefits as probiotics for enhancing host defense mechanisms in C. elegans.