Intestinal microbiota analysis and probiotic application in gamat sea cucumber ( Stichopus horrens )

Abstract

Gamat sea cucumber (Stichopus horrens) is an commercially valuable sea cucumber that is rich in nutritional values and pharmacological properties. This study aimed to explore the microbiota in the intestinal tract of S. horrens using high-throughput sequencing, based on the 16S rRNA gene sequences. Proteobacteria was found to be predominant phylum. Vibrio was the top genus in the anterior (AI) and the posterior (PI) parts of the intestine of S. horrens, while some genera were different between two parts. These results suggested that the bacteria in the AI were associated with fermentation and bile acid biosynthesis processes, while those in the PI functioned as helper cells in digestion processes in the host. In this study, Firmicutes phylum of lactic acid bacteria was found, so the probiotic bacteria were selected for sea cucumber aquaculture application. We found Pediococcus pentosaceus strain SH1 grew well at a wide range of pH and high NaCl concentrations, which was suitable for survival in seawater. In feeding trial study, P. pentosaceus SH1 significantly (p < 0.05) increased the survival rate of larvae in the first period (Day 4) of larvae culture and also improved water quality by converting total ammonia nitrogen to nitrite and reducing nitrate levels in the water system. In conclusion, P. pentosaceus SH1 has the potential to increase the survival rate of larvae and improve water quality in sea cucumber aquaculture.