Creative Commons License

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

Preferred Name

Sarah McGrath

Date of Award

Summer 2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Department of Biology

Advisor(s)

David S. McLeod

Morgan Steffen

Reid Harris

Abstract

Characterization of microbial biodiversity, including that of the amphibian skin-associated microbiome, is a frontier of research recently made accessible through advances in sequencing technology. Microbial interaction with a host has been determined to have profound influences on host health across a wide range of macroscopic organisms. For amphibians, the influence of the skin-associated microbiome has been found to have particular importance, as amphibians are currently one of the fastest disappearing vertebrate groups on the planet, largely in part to skin-associated diseases caused by pathogenic microbes. Therefore, it is important to characterize the amphibian skin-associated microbiome, particularly for species with no existing microbiome data, and to delineate relationships that may influence host health. In determining the microbial community of amphibian skin, it is important to outline baseline native microbial presence and gain insight into how these microbes become established. This study focused on being the first to characterize the cutaneous microbial diversity of three Southeast Asian tree frogs in the family Rhacophoridae (genus: Polypedates) that reproduce via the specialized breeding strategy of building a foam nest and comparing the amphibian microbiome across initial development to that of the environment. Microbes associated with reproducing adults, foam nests, tadpoles before and after environmental interaction, and the surrounding environment were characterized using 16S amplicon sequencing. The phylum Proteobacteria comprised the majority of communities across amphibian and environmental samples at 57% relative abundance with Firmicutes (16%) and Bacteroidetes (13%) as the next most dominant phyla. In comparing amphibian and environmental samples, no amphibian microbial communities mirrored that of their immediate environment. Interestingly, tadpole skin-associated microbes differed in relative abundance and microbial taxa between nest-extracted tadpoles and those that were sampled after interaction with a pond environment. This demonstrates the necessity of further research into microbial community establishment, host selection processes, and microbial transmission. Gaining baseline knowledge of the skin-associated microbiome contributes to our knowledge of the natural world and preliminary delineation of ecological relationships between host, microbe, and environment provides an example of the need for continued research in this area which has the potential to broadly inform conservation efforts for amphibians worldwide.

Available for download on Saturday, June 29, 2019

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