Exposure to copper altered the intestinal microbiota in Chinese brown frog ( Rana chensinensis )

The intestinal microbiota is a crucial physiological system that offers multiple services to the host and contributes to the health of host. However, substantially less is known concerning the interrelation between amphibian gut microbiota and Cu exposure. R. chensinensis larvae were exposed to different concentrations of Cu (0, 0.1, 0.25, 0.75 μM) until reached Gosner stage 38. Histological and morphological data were measured by four Cu exposure conditions. Then, the diversity, structure, and composition of intestinal microbiota were analyzed via 16S rRNA gene sequencing. These results indicated that total body length, intestinal wet weight, and total body wet weight were reduced in 0.75 μM CuSO4 exposure group. Besides, obvious histopathologic alterations were observed in CuSO4 exposure groups. Alpha diversity significantly differentiated in 0.75 μM CuSO4 exposure group, and beta diversity showed 0.1 μM and 0.2 μM CuSO4 exposure groups separation with the control group. At the phylum level of intestinal microbial community, the relative abundances of Fusobacteria were significantly decreased, while Bacteroidetes was no significant difference in all CuSO4 exposure groups. Furthermore, at the genera level, Flavobacterium has a significant higher abundance in 0.75 μM CuSO4 exposure group, and high abundance of Rahnella was found in 0.1 μM CuSO4 exposure group. Also, Cu exposure affected the metabolism function of R. chensinensis tadpoles based on functional prediction analysis. This work provides new perspective to explore the effect of heavy metal on the intestinal health of amphibians.