Date of Award

Spring 5-2013

Degree Type

Honors College Thesis


Biological Sciences

First Advisor

Glen Shearer

Advisor Department

Biological Sciences


Histoplasma capsulatum is a dimorphic fungus that causes the respiratory disease histoplasmosis. At 25°C, the fungus grows as a multicellular mold in soils contaminated by bird and bat excreta. Once the soil is disturbed, spores are released and inhaled into the lungs. The fungus shifts to a unicellular, pathogenic yeast within the lungs at 37°C. Our laboratory’s main objective is to characterize the genes that are involved in the mold-to-yeast dimorphism. This study focuses on the mold-specific gene, MS95. According to The Broad Institute Histoplasma capsulatum GenBank Blastx search, MS95 has several homologs, including the well-studied Saccharomyces cerevisiae. MS95 belongs to a gene family of stress proteins known as DDR (DNA Damage Responsive) and is believed to repair DNA damaged by heat stress. To better determine the function of MS95, this project explains the creation of a MS95 knockout by allelic replacement. The MS95 knockout was confirmed by a Southern blot. Mold and yeast growth curves of the MS95 knockout did not show any significant changes in the rate of growth when compared to the Wu27 wild type strain. Comparisons of the yeast and mold morphology in both liquid and solid media showed no significant difference between the MS95 knockout and the Wu27 wild type strain. These findings suggest that MS95 is not involved in dimorphism. Future studies will include observing how MS95 knockout and Wu27 wild type strains react to different stressors and overexpressing MS95 in the yeast phase growing temperature to confirm that it is not involved in dimorphism.

Included in

Life Sciences Commons