Kenneth W. Nickerson
Date of this Version
Ahmad Hussin, N. 2016. The Roles of Biotin in Candida albicans Physiology. MS Thesis. University of Nebraska-Lincoln.
Due to the increased number of immunocompromised patients, infections by Candida albicans have significantly increased in recent years. C. albicans transition from yeast to germ tubes is an essential factor for virulence. In this study we noted that Lee's medium, commonly used to induce filamentation, contained 500-fold more biotin than needed for growth. Thus, we investigated the effects of excess biotin on growth rate and filamentation by C. albicans in different media. At 37 °C, excess biotin (4 µM) enhanced germ tube formation (GTF) ca. 10-fold in both Lee's medium and a defined glucose proline medium, and ca. 4-fold in 1% serum. Desthiobiotin, KAPA, and lipoic acid also stimulated GTF and are able to fulfill the biotin auxotrophy requirement. The mechanism by which excess biotin enhances GTF is still unknown except to note that equivalent levels of biotin are needed to create an internal supply of stored biotin. Biotin did not restore filamentation for any of the four known filamentation defective mutants tested. We also found that biotin auxotrophy is not temperature dependent nor influenced by the presence of 5% CO₂. Biotin starvation upregulated the biotin biosynthetic genes BIO2, BIO3, and BIO4 by 11-, 1500-, and 150-fold, respectively, and BIO2p is predicted to be mitochondrion-localized. Based on our findings, we suggest that biotin has two roles in the physiology of C. albicans, one as an enzymatic cofactor and another as a morphological regulator.
Advisor: Kenneth W. Nickerson