Abstract

Batrachochytrium dendrobatidis (Bd) is an emerging fungal skin pathogen of amphibians that has affected frog and salamander populations across the globe. Some populations appear to tolerate Bd better than others, and there is evidence that bacteria of the amphibian skin microbiome may play a role in this phenomenon. The relationship between Bd and amphibians is not only an issue of great conservation significance, but studying it can shed light on host-pathogen interactions more generally, particularly the role microbes play in disease dynamics of wild organisms. In this study, skin swabs were collected from northern two-lined salamanders and analyzed for the presence of Bd using qPCR. Then, the microbiomes of Bd positive and Bd negative individuals were characterized using 16s v3-v4 metagenomic sequencing and compared.

Of the salamanders sampled in this study, 6.1% (n = 98) were positive for Bd. This study is the ninth year of sampling for Bd in this population, and, across all years, 13.6% of salamanders were positive for Bd (n = 704). Over the past nine years, there was a significantly higher frequency of Bd prevalence in 2020 and 2022. There were also significant differences in the frequency of Bd between creeks sampled over the past nine years.

Metagenomic sequencing revealed that various genera known to contain Bd-inhibiting species were present on all individuals sequenced (n = 15). One family of bacteria, Alcaligenaceae, was significantly more abundant on Bd negative salamanders (n = 8). One uncultured phylum, GAL15 (Sysuimicrobiota), was significantly more abundant on Bd positive salamanders (n = 7). These results suggest that Bd is in the enzootic phase of disease within our population, and that Bd-inhibiting bacteria are common both on Bd positive and negative salamanders.

Advisor

Lehtinen, Richard

Department

Biology

Disciplines

Environmental Microbiology and Microbial Ecology | Evolution

Keywords

Batrachochytrium dendrobatidis, salamanders, microbiome

Publication Date

2025

Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis

Available for download on Thursday, July 25, 2030

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© Copyright 2025 Will Wasielewski