Date of Award

12-31-2022

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Sciences

First Advisor

Douglas C. Woodhams

Second Advisor

Catherine McCusker

Third Advisor

Jarrett Byrnes

Abstract

As fungal diseases continue to emerge, research increasingly focuses on host-microbiome interactions and links to disease. Certain skin-associated microbes may benefit hosts by protecting them from invading pathogens. Seasonal changes in the host environment can also result in shifts in the microbial community and pathogen virulence – potentially influencing disease dynamics. I investigated how cutaneous microbial communities differ across hosts, seasons, and Batrachochytrium dendrobatidis (Bd) infection status by sequencing the microbial communities of 1,100 leopard frogs at five locations across the US. Percent anti-Bd function varied seasonally and with Bd infection status. Bacterial communities also varied across locations and time.

By culturing microbes and testing them against multiple fungal pathogens, we can develop effective probiotics to mitigate disease across ecosystems. I also selected 60 bacterial isolates and tested their airborne volatile organic compound (VOC) antifungal activity against six devastating wildlife pathogens. Most exhibited strong antifungal activity against several pathogens and we then selected 7 isolates for further SPME-GCMS analysis to identify VOCs of interest.

Host species also differ in their response to disease, and the role of alternative hosts in Bd transmission is not well known. To explore species-specific differences, I evaluated the role of an invasive species of crayfish (Orconectes rusticus) as a non-amphibian host to both Bd and B. salamandrivorans and assessed their ability to effectively transmit infection to amphibians. As the range of this crayfish expands across many parts of the United States, its potential to act as an alternative host may drive increased transmission in naïve or susceptible frog populations. Better understanding of the complex interactions between host, microbes, and the environment can lead to elucidating disease transmission potential and more effective measures to combat wildlife pathogens.

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