Probiotic lactic acid bacteria isolated from Thai fermented foods and their lifespan-extending effect in Caenorhabditis elegans

Abstract

Fermented food is an excellent natural source of probiotic bacteria. This study aimed to isolate and identify probiotic lactic acid bacteria (LAB) from Thai fermented foods. Their potential in extending lifespan was investigated in Caenorhabditis elegans (C. elegans) model. Eighteen types of Thai fermented food samples from different regions of Thailand were collected, and LAB were screened based on calcium carbonate solubilization. Twenty-seven colonies with prominent clear zones were selected and subjected to 16S rRNA gene sequencing for initial identification. All 27 isolates were screened for lifespan extending activity in C. elegans, and 15 of them caused significant increase in C. elegans lifespan relative to control. Three isolates including ThaiPMG8 (from Pak Gard Dong), Neam5.2 (from Neam), KSPLB4.3 (from Pla Ra) were chosen for further longevity experiments using the reference Lacticaseibacillus rhamnosus (LGG) as positive control. The results demonstrated that supplementation with these three LAB obviously exhibited the lifespan extending activity in C. elegans. However, combination of these LAB (2-3 strains) did not show the additive or synergistic effects in lifespan extension compared with the single-strain supplementation. Among these three tested isolates, the ThaiPMG8 strain exhibited the highest efficacy in increasing the C. elegans lifespan (38.46%) compared with the E. coli OP50 control, and it was selected for further whole genome sequencing (WGS). To elucidate the underlying molecular mechanisms of the lifespan-extending function of ThaiPMG8, Neam5.2, KSPLB4.3, and LGG, lifespan assays were investigated in C. elegans mutants (daf-2, daf-16, and skn-1 mutants) and determined the mRNA expression by RT-qPCR. The findings revealed that the selected LAB extended lifespan through the Insulin/IGF-1 signaling (IIS) pathway (involving daf-2 and daf-16) and the p38 MAPK pathway (involving skn-1). Based on the WGS data, ThaiPMG8 was identified as a new strain and designated Lactiplantibacillus plantarum ThaiPMG8. Bioinformatic analysis demonstrated that L. plantarum ThaiPMG8 contained a number of genes related to probiotic function (e.g., gadB, nhaC, mtr, and inl ), antioxidant system (e.g., cat, npx, gshP, and dnaJ), and longevity(e.g., ribF, ltaS, and ackA). In conclusion, this study successfully isolated the LAB from Thai fermented foods. ThaiPMG8, Neam5.2, and KSPLB4.3 exhibited excellent lifespan-extending effects in C. elegans models, particularly the ThaiPMG8 isolate. The WGS data of ThaiPMG8 clearly indicated that it was a new strain. Based on the present findings, this novel L. plantarum ThaiPMG8 strain was a promising probiotic LAB with a potent lifespan-extending activity that could provide a health benefit for promoting longevity in human.