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Amphibians worldwide are under threat from the infectious disease chytridiomycosis, which is caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). Bd is associated with the population declines of an estimated 501 species, 90 of which are presumed or confirmed extinct, making this the greatest documented loss of biodiversity attributed to a disease. Researching the amphibian skin microbiome may provide solutions to conservation of amphibians. Two main relationships have been observed between Bd and the microbiome: 1) bacteria producing antifungal metabolites can inhibit Bd and improve survival against the disease and 2) infection by Bd is believed to affect the composition of the skin microbiome. In collaboration with the Idaho Department of Fish of Game, Columbia spotted frogs (Rana luteiventris) from northern Idaho were swabbed to detect Bd and collect bacteria from the skin microbiome. Our study found Bd was prevalent in low infection intensities in 80% of 153 sites in the northern Idaho panhandle. Amplicon barcoded sequencing of the V4-V5 region of the 16S rRNA gene was performed to characterize the skin microbiome of frogs. Overall, the most abundant groups of bacteria on the skin were Burkholderiaceae, Pseudomonas spp., Stenotrophomonas spp., Sanguibacter inulinus, and Enterobacteriaceae. Results demonstrated skin microbiomes were distinct in infected and uninfected frogs, with key differences including greater relative abundance of Burkholderiaceae in infected frogs and greater relative abundance of Pseudomonas in uninfected frogs. Columbia spotted frogs and Pacific chorus frogs (Pseudacris regilla) were swabbed at Turnbull National Wildlife Refuge (TNWR) to measure Bd prevalence and infection intensity. Prevalence among Pacific chorus frogs (91.43%) was greater than prevalence among Columbia spotted frogs (67.74%), and infection intensities were also greater among Pacific chorus frogs compared to Columbia spotted frogs. Preliminary microbiome results showed a correlation between microbiome communities and infection intensity. Continued research on the amphibian skin microbiome could lead to the development of more effective probiotics as a conservation solution to population decline in amphibians.
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Campos, Philip M., "Impact of Chytrid fungus pathogen on the skin microbiome of frogs in northern Idaho and Turnbull National Wildlife Refuge, Washington" (2020). EWU Masters Thesis Collection. 606.