Manipulation of cadmium and diethylhexyl phthalate on Rana chensinensis tadpoles affects the intestinal microbiota and fatty acid metabolism

Gastrointestinal tract and intestine microbiota can both have deep effects on the lipid metabolism and immune function of amphibians. Additionally, the composition and structure of the microbial community are influenced by environmental pollutions. It is noteworthy that environmental compounds such as Cd and DEHP are pervasive in the aquatic environment and do not exist in isolation, and single exposure experiments cannot well explain the effects of unpredictable interactions between co-existing compounds on amphibians. In this study, we calculated the parameters of morphological and histological indices of Rana chensinensis tadpoles after treated with Cd and/or DEHP. The 16S rRNA gene sequencing technology was used to assess the relative abundance of intestinal microbial community among tadpoles from each treatment groups. We also examined the mRNA expression levels of lipid digestion and absorption and SCFAs related-genes. Our results indicated that all morphological and histological indices were significantly declined in the Cd treatment group, while the mixed treatment group was similar to the control group. Compared with the control group, the relative abundances of Firmicutes, Proteobacteria and Verrucomicrobia exhibited distinctive differences in Cd and/or DEHP treatment groups. Further, RT-qPCR results revealed that the expression levels of lipid metabolism and SCFAs related-genes were also significantly altered among the treatment groups. Taken together, the present study highlighted a new evidence that the alterations in intestinal microbial community and mRNA expression levels of larval amphibians after exposure to Cd and/or DEHP may impair lipid storage and transport, as well as reduce anti-inflammatory capacity, which may ultimately lead to a decline in amphibian populations.