Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Date of Award

Spring 2013

Document Type


Degree Name

Master of Science (MS)


Department of Biology


Beneficial cutaneous bacteria on amphibians can protect against the lethal fungal disease chytridiomycosis, which has decimated many amphibian species. The stability of these bacterial communities likely influences health outcomes, and is investigated here for the first time. We describe the diversity of bacteria on red-backed salamanders (Plethodon cinereus) in the wild, and the stability of these communities over time in captivity using culture-independent Illumina sequencing. In the field, there was no correlation between the diversity of salamanders’ microbial communities and the diversity of their substrates’ microbial communities. Salamanders were brought into the laboratory to test for the effect of an environmental reservoir (soil) in maintaining diversity and stability and were sampled every 7 days ending at day 28. In the laboratory, the alpha diversity of salamanders in the ‘no bacterial reservoir’ treatment decreased, whereas it remained constant in the ‘bacterial reservoir treatment’. The treatment groups diverged from each other, yielding significant differences in beta-diversity. Eight OTUs defined a core community, i.e., present on >90% of salamanders through time, and a majority of these taxa such as Pseudomonadaceae, are known to secrete antifungal metabolites. Alpha diversity decreased in the treatment lacking a soil reservoir, one core OTU from the phylum Verrucomicrobia dominated the community. This result suggests that the non-core community on the salamanders regulate the core community and that the non-core community is dependent on the soil reservoir. Bacterial community structure in both treatments changed when their salamander hosts were brought into the laboratory. Diversity was more constant in the bacterial reservoir treatment. Defensive function of salamanders’ cutaneous microbiota may depend on the diversity and stability of the core community.

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