Date of Award

Fall 2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Biological, Environmental, and Earth Sciences

Committee Chair

Glenmore Shearer Jr.

Committee Chair School

Biological, Environmental, and Earth Sciences

Committee Member 2

Janet Donaldson

Committee Member 2 School

Biological, Environmental, and Earth Sciences

Committee Member 3

Mohamed Elasri

Committee Member 3 School

Biological, Environmental, and Earth Sciences

Committee Member 4

Alex Flynt

Committee Member 4 School

Biological, Environmental, and Earth Sciences

Committee Member 5

Shahid Karim

Committee Member 5 School

Biological, Environmental, and Earth Sciences

Abstract

Histoplasma capsulatum(Hc)is a systemic, dimorphic fungal pathogen that affects upwards of 500,000 individuals in the United States annually. Hc grows as a multicellular mold at environmental temperatures; whereas, upon inhalation into a human or other mammalian host, it transforms into a unicellular, pathogenic yeast. The research presented in this dissertation is focused on characterizing the DNA damage-responsive gene HcDDR48. HcDDR48was originally isolated via a subtractive DNA library enriched for transcripts enriched in the mold-phase of Hcgrowth. Upon further analysis we found that HcDDR48is not just expressed in the mold morphotype, but both growth programs dependent upon the environment. Since the yeast phase of Hcis the phase that interacts with the host, the research in this dissertation focused solely on HcDDR48’s involvement in yeast-phase Hc. We found that HcDDR48is involved in oxidative stress response, antifungal drug response, and survival within resting and activated macrophages. Growth of ddr48Dyeasts was severely decreased when exposed to the reactive oxygen species generator paraquat, as compared to wildtype controls. We also found that ddr48Dyeasts were 2-times more sensitive to the antifungal drugs amphotericin b and ketoconazole. To testHcDDR48’s involvement in vivo, we infected resting and activated RAW 264.7 murine macrophages with Hcyeasts and measured yeast survival 24-hours post-infection. We observed a significant decrease in yeast recovery in the ddr48Dstrain compared to wildtype Hclevels. Herein, we demonstrate the importance of maintaining a functional copy of HcDDR48in order for Hcyeasts to sense and response to numerous environmental and host-associated stressors.

ORCID ID

https://orcid.org/0000-0003-4662-6554

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