Bacillus licheniformis Isolated from Korean Traditional Food Resources Enhances the Lifespan of Caenorhabditis elegans through Serotonin Signaling

Abstract

Here, we examined potentially probiotic Bacillus spp. with antimicrobial activities from Korean traditional food sources, and evaluated their enhanced longevity using the nematode Caenorhabditis elegans as a simple in vivo animal model. Initially, we selected twenty probiotic Bacillus spp. that produced antimicrobial bacteriocins against various foodborne pathogens. Unexpectedly, plate counting and transmission electron microscopy (TEM) results indicated that the Bacillus spp. strains were not persistent on the C. elegans intestine compared with E. coli OP50 or Lactobacillus rhamnosus GG controls. Next, we determine whether selected Bacillus spp. is capable for modulating the lifespan of C. elegans. Among the tested strains, the pre-conditioning by four Bacillus spp. significantly enhanced the longevity of C. elegans. In addition, qRT-PCR and aging assay with transgenic mutant worms showed that the conditioning of selected Bacillus spp. directly influence on the genes associated with serotonin signaling of nematode including tph-1 (tryptophan hydroxylase), bas-1 (serotonin- and dopamine-synthetic aromatic amino acid decarboxylase), mod-1 (serotonin-gated chloride channel), and ser-1 (serotonin receptors) during aging of C. elegans. Based on 16S rRNA sequencing, the selected strain was identified as B. licheniformis. Our findings propose that probiotic Bacillus spp. isolated from Korean traditional foods may enhance the lifespan of C. elegans via serotonin signaling in host.