Erin M. Smith

Date of Award


Degree Type

Honors College Thesis


Biological Sciences

First Advisor

Glen Shearer, Ph.D.

Advisor Department

Biological Sciences


Histoplasma capsulatum (Hc) is a dimorphic fungus that is the etiologic agent of the respiratory infection Histoplasmosis that is mediated by a shift from the mold phase to the pathogenic yeast phase. Genes have been identified that are specific to the mold or yeast phase in order to study the molecular biology of this shift. MS95 was identified in a subtractive cDNA library that was enriched for mold-specific genes, and has been found to be homologous to the DNA damage-responsive gene DDR48, which functions in DNA repair in Saccharomyces cerevisiae. In order to elucidate the function of MS95, a loss of function mutant was created via allelic replacement. To determine if MS95 is involved in DNA repair, wild-type and MS95 knockout mutant strains were grown on Histoplasma macrophage media (HMM) supplemented with varying concentrations of 4-nitroquinoline 1-oxide (4-NQO) or paraquat dichloride. Growth was monitored for any changes between the two strains indicating that MS95 plays a role in DNA repair. To confirm the results, the knockout mutant was complemented, and these complements were analyzed via real-time PCR. There was a significant difference in growth between the wild-type and knockout mutant strains when grown on plates that contained 40 and 60uM paraquat. There was not a significant difference observed between the two strains when grown on media containing 4-NQO. The results of the RT-PCR show that expression of MS95 was restored, thus confirming successful complementation.