Effects of endogenous potential probiotic Lactobacillus rhamnosus M2-4 on intestinal microflora and metabonomics in juvenile sea cucumber Apostichopus japonicus

As a lactic acid bacteria, Lactobacillus is an important probiotic used in aquaculture. Intestines play an important role in beneficial function of probiotic. But little is known about the mechanism of lactic acid bacteria effecting on the intestines of sea cucumber Apostichopus japonicus. Herein, the present study was designed to explore the effects of endogenous Lactobacillus rhamnosus M2-4 on the intestinal microflora and metabolism of juvenile A. japonicus with high-throughput sequencing and metabonomics technology. The basal diet was Sargassum thunbergii powder, which was added with M2-4 at 0, 10(5), 10(7) and 10(9) CFU / g to form the experimental diet respectively. The feeding experiment lasted for 30 days. The results showed that dietary M2-4 had a significant effect on intestinal microbial composition of sea cucumber. With the increase of dietary M2-4, the relative abundance of potential probiotics including Haloferula (Verrucomicrobia), Rhodobacteraceae and Lactobacillus were increased and the potential pathogens especially Vibrio were decreased. And dietary M2-4 at 109 CFU / g was beneficial to its self-colonization in the intestines of A. japonicus. Metabonomics analysis showed that the differential lipid metabolites were increased and lipid metabolism pathways were enriched with the increase of dietary M2-4. The highest enriched pathway in the intestines of A. japonicus were mTOR and PPAR signaling pathway and the mostly influenced pathways were glutathione and linoleic acid metabolism pathway. The correlation analysis of intestinal microflora and main differential metabolites indicated that the differential metabolites were mostly correlated to the strains of Flavobacteriaceae. These results shed some light on the mechanism of lactic acid bacteria Lactobacillus influencing the intestine of juvenile sea cucumber A. japonicus.