From Skin to Gut: Understanding Microbial Diversity in Rana amurensis and R. dybowskii.

Amphibians face the threat of decline and extinction, and their health is crucially affected by the microbiota. Their health and ecological adaptability essentially depend on the diverse microbial communities that are shaped by unique host traits and environmental factors. However, there is still limited research on this topic. In this study, cutaneous (C) and gut (G) microbiota in Rana amurensis (A) and R. dybowskii (D) was analyzed through 16S amplicon sequencing. Groups AC and DC significantly differed in alpha diversity, while the gut groups (AG and DG) showed no such differences. Analyses of Bray-Curtis dissimilarity matrix and unweighted UniFrac distances showed significant differences in cutaneous microbiota between groups AC and DC, but not between groups AG and DG. Stochastic processes significantly influenced the assembly of cutaneous and gut microbiota in amphibians, with a notably higher species dispersal rate in the gut. The predominant phyla in the skin of R. amurensis and R. dybowskii were Bacteroidetes and Proteobacteria, respectively, with significant variations in Bacteroidota. Contrarily, the gut microbiota of both species was dominated by Firmicutes, Proteobacteria, and Bacteroidetes, without significant phylum-level differences. Linear discriminant analysis effect size (LEfSe) analysis identified distinct microbial enrichment in each group. Predictive analysis using phylogenetic investigation of communities by reconstruction of unobserved states 2 (PICRUSt2) revealed the significant functional pathways associated with the microbiota, which indicates their potential roles in immune system function, development, regeneration, and response to infectious diseases. This research underscores the critical impact of both host and environmental factors in shaping amphibian microbial ecosystems and emphasizes the need for further studies to explore these complex interactions for conservation efforts.