*WINNER* Identifying patterns in the culturable skin microbiome of Appalachian salamanders

Abstract

Batrachochytrium dendrobatidis (Bd) is a fungal pathogen that has devastated amphibian populations worldwide.  However, in the eastern United States, salamander populations persist in the presence of this fungus with relatively low rates of infection.  We hypothesize that probiotic species within the salamander cutaneous microbiome protect their host by inhibiting growth of Bd.  During previous work, we identified cutaneous defenses of salamanders by isolating bacteria from skin swabs and challenging them against Bd.  The objectives of our current work are to (1) characterize the microbiome through 16S sequencing techniques, and (2) determine whether the culturable microbiome differs based on host species and/or habitat. Salamanders belonging to the genera Desmognathus (n = 8), Eurycea (n = 7), and Plethodon (n = 7) were sampled in the Great Smoky Mountains National Park. From their skin swabs, we obtained and sequenced a total of 110 bacterial isolates. Bioinformatics analyses were conducted using the software mothur, and a two-way permutated multivariate analysis of variance was conducted in Primer7. Preliminary results indicate that differentiation exists between the microbiome of terrestrial and aquatic salamanders. In addition, 81% of inhibitory isolates occurred on Plethodon glutinosus salamanders, and Gram-positive bacilli accounted for 38% of inhibitory isolates. During future work, we will compare our findings to the high-throughput sequencing dataset to confirm if these patterns hold true.  We hope our work will pinpoint the best candidate probiotics and help establish a procedure for treating amphibians infected with Bd.