Undergraduate Honors Theses

Thesis Defended

Spring 2019

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Ecology and Evolutionary Biology

First Advisor

Valerie McKenzie

Second Advisor

Barbara Demmig-Adams

Third Advisor

Amy Palmer

Abstract

The microbial community of amphibians skin has demonstrated significant importance in amphibian health and disease resistance specifically in response to the pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd; Barnhart et al. 2017). Since its discovery in the late 1990s, Bd has contributed to world-wide decline in amphibian populations. Multiple naturally occurring amphibian-skin bacteria have been identified as inhibitors of Bd, including Janthinobacterium lividum (J liv; Harris et al. 2009). The McKenzie group developed a probiotic treatment of J liv as an intervention for a boreal toad population in Colorado drastically declining due to a Bd epidemic. Since wild toads cannot be directly exposed to Bd, mucosome soaks were collected to test the effectiveness of the treatment. The mucosome soak captures a sample of the bioactivity of the skin mucus, including any host-produced peptides and microbially produced metabolites for in vitro testing in the lab. My thesis developed and tested three different assays to determine the most consistent and sensitive way to assess inhibition of Bd by the mucosome soaks. The assays treated Bd zoospores with inhibitory metabolites of J liv and quantified three different aspects of zoospore health, (1) growth, (2) membrane integrity, and (3) ATP concentration. While each assay was effective in unique ways, the growth assay was the most sensitive and the luminescence assay was the most consistent. These assays will help predict which amphibian individuals possess skin mucus that is highly inhibitory to the Bd pathogen, and determine whether probiotic treatments are effective at increasing skin defenses. The use of probiotics represents a novel tool for amphibian conservation and the mucosome assay is an important part of testing the efficacy of probiotic approaches.

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