Award Date

5-15-2026

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Committee Member

Ernesto Abel-Santos

Second Committee Member

Hong Sun

Third Committee Member

Balakrishnan Naduvalath

Fourth Committee Member

Paul Schulte

Number of Pages

198

Abstract

Nearly 50% of amphibian species are at risk of extinction, making them the most threatened group of vertebrates on the planet. A major driver of these declines is the pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd), which causes the fatal skin disease chytridiomycosis. Since its discovery in the late 1990s, Bd has been directly implicated in the extinction of 90 species of amphibians and the declines of hundreds more. Despite this devastating ecological impact, relatively little is known about its basic cellular biology.

Bd has a multi-stage asexual life cycle consisting of a motile and infectious zoospore, which encysts (into a “cyst”), germinates (into a “germling”), and matures into zoosporangia that release new zoospores. This work examines the nutritional signals that influence differentiation, the effects of differentiation on metabolism, and the cellular response to exposure to different nutritional signals.

First, the nutritional requirements of Bd life cycle progression were investigated. Differentiation is primarily driven by nitrogen sources: Hydrophobic and basic amino acids promoted encystment and germination, while protein sources differentially enhanced zoosporangia formation and maturation. Notably, we found that crude keratin of amphibian and reptile origin, but not bird origin, significantly enhanced the differentiation of Bd to later stages of its life cycle.

Second, the metabolic behavior of Bd was measured using optimized viability assays of several different molecular mechanisms. In each case, the metabolic output of Bd correlated most strongly with cell size, rather than developmental stage, indicating that morphological growth is the primary determinant of metabolic activity.

Because Bd strictly infects the keratinized epithelium of its amphibian hosts, the effects of exposure to crude keratin from different sources on the secretome of Bd were investigated. Distinct patterns of secreted proteins were observed in the presence of reptile scales, bird feathers, or no keratin source, indicating that Bd modulates is protein secretion in response to different keratin substrates.

These findings describe how the development and physiology of Bd are shaped by environmental and nutrient cues. This study provides a foundation for further investigating the mechanisms by which Bd recognizes and infects its hosts and persists in natural environments in the absence of amphibians.

Keywords

amphibian pathogen; chytrid fungus; chytridiomycosis; fungal development; fungal secretome; nutrient sensing

Disciplines

Biochemistry | Life Sciences | Microbiology

File Format

PDF

File Size

6900 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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