Comparison of intestinal microbial diversity and bile acid profile between Bufo gargarizans and Rana chensinensis tadpoles

Bile acids (BAs) are cholesterol derivatives synthesised by the liver, exhibit variation between different species. Researchers have long appreciated the roles that microbiota play in the biotransformation of BAs.However, relatively few studies have been reported on microbial-mediated production and transformation of BAs in amphibians. Our focus here is principally on difference of intestinal microbial diversity and BAs profiles between two common amphibians, Bufo gargarizans and Rana chensinensis tadpoles, through intestinal targeted BAs metabolomics and fecal metagenomic sequencing.The results demonstrated that B. gargarizans possess higher levels of total BAs and higher ratio of unconjugated/conjugated BAs. In addition, the relative abundance of microbiota with bile salt hydrolase (BSH) activity in B. gargarizans was significantly higher than that of R. chensinensis, thus facilitating the conversion of conjugated to unconjugated BA.Meanwhile the higher prevalence of bile-acid-induced (bai) gene encoding microbiota in R. chensinensis may promote the synthesis of deoxycholic acid (DCA).Furthermore, discrepancies in virulence factors and energy metabolism were observed between the two species, which may be linked to differences in the microbiota. This study reveals substantial differences in intestinal microbes and BAs across amphibian species, emphasizing the significant impact of intestinal microbes on BAs metabolism.