Honors Program

Midway Honors, Honors in Health Sciences: Microbiology

Date of Award


Thesis Professor(s)

Michael Kruppa

Thesis Professor Department


Thesis Reader(s)

Karen Kornweibel, Laraine Powers


Candida albicans is an opportunistic pathogen that is present in the normal flora in a majority of individuals. One key factor in C. albicans virulence is the ability to change its morphology from yeast to an elongated or hyphal form. The regulation of this morphogenesis relies in part upon quorum sensing (QS) molecules. C. albicans often exists as part of a mixed culture alongside other microbes and is influenced by their presence as well as the presence of QS molecules that they produce. In this study, a library of diploid homozygous transcriptional regulator knockout (TRKO) mutants were screened to identify strains capable of forming hyphae in the presence of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli. We identified three strains that showed increased hyphae development compared to wild type C. albicans. The strains identified had deletions of the transcriptional regulating genes Orf19.3928, Orf19.2842 (GZF3), and Orf19.3865 (RFX1). These strains were tested for alterations of filamentation in liquid media, and biofilm formation. All three strains showed increased rates of biofilm formation compared to the wild type. Orf19.3928 showed altered response to farnesol, a marked in biofilm formation and no inhibition of filamentation when farnesol was present in liquid media. The GZF3 deletion strain showed enhanced filamentation with all three bacterial species while the RFX1 deletion strain showed increased filamentation only with E. coli and S. aureus. In spent media, GZF3 showed slight increases in filamentation in E. coli and S. aureus while RFX1 had moderate increases in filamentation in E. coli and S. aureus and slight increases with P. aeruginosa.

Document Type

Honors Thesis - Withheld

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