Date of Award

Spring 2023


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Document Type


Degree Name

Master of Science (MS) in Biology




Amphibian populations are declining due to a variety of threats, including the chytrid fungal pathogen, Batrachochytrium dendrobatidis (Bd), the causative agent of the disease chytridiomycosis. Climate change and other stressors can have complicated interactions with amphibian disease. Some amphibian populations are less susceptible to chytridiomycosis due to factors such as symbiotic skin microbes that may inhibit Bd through secondary metabolites. There have been several attempts to develop probiotics from these symbiotic, antifungal bacteria to provide protection against Bd infection, but these studies have had mixed success. Our study evaluated anti-Bd bacteria isolated from the skin of Pacific chorus frogs (Pseudacris regilla) and Columbia spotted frogs (Rana luteiventris) in Turnbull National Wildlife Refuge (TNWR) as potential probiotics. One of these isolates, identified as Pseudomonas silesiensis, was tested as a probiotic treatment on P. regilla. Sixty frogs were collected from TNWR and randomly assigned to six treatment groups: probiotic and Bd addition, Bd only, and control, each divided into historical temperature treatments and future climate change temperatures treatments. Frogs were housed at their respective climate treatments, exposed to the probiotic or sham treatment, then exposed to Bd or a sham treatment two weeks later. Frogs were swabbed, weighed, and measured at multiple timepoints to determine sublethal impacts of Bd, infection intensity, infection prevalence, and microbiome impacts of treatments. No frogs were found to have Bd in the field, and infection prevalence throughout the experiment remained low, even after exposure to Bd. Infection intensity was generally low, although one frog did have an infection intensity of 11,100 zoospore equivalents. Probiotic treatment did not significantly impact Bd prevalence (Fisher’s exact test: p=1.0) or infection intensity (ANOVA: df=1, f=0.3225, p=0.60983). Climate treatments also did not significantly impact infection intensity (ANOVA: df=1, f=0.1439, p=0.7297) or prevalence (Fisher’s exact test: p=1.0). These results can inform future probiotic efforts and provide insight into impacts of climate change temperatures on Bd-host-microbiome interactions.