Chitin Levels and Cell Death in Saccharomyces cerevisiae Smi1-∆ Cells Exposed to Antifungal Treatment

Abstract

The SMI1 gene plays an integral role in the coordination of a cell wall integrity (CWI) pathway in Saccharomyces cerevisiae. Thus, smi1-∆ mutant cells present cell wall defects due to their reduced capacity to synthesize cell wall components. Responding to weakened cell walls, yeast cells produce increased amounts of chitin as a compensatory mechanism. It was hypothesized that smi1-∆ cells will present lower cell death rates, increased chitin levels, and therefore present an increased tolerance to antifungals. Wildtype-a (WTa) cells, and smi1-∆ cells were treated with imidazole to study antifungal effects on cell viability and chitin production in smi1-∆ S. cerevisiae cells. To examine the effects of an antifungal stressor, cell death was quantified using hemocytometry and chitin levels were visualized using fluorescence microscopy. Imidazole-exposed smi1-∆ cells exhibit significantly lower cell death percentages. smi1-∆ cells have significantly higher cell wall chitin levels than WT-a cells and display further increases with antifungal treatment. These  findings indicate that CWI pathway disruption in smi1-∆ cells may lead to an increased antifungal-tolerance. Examining interrupted CWI pathway compensatory mechanisms in mutant S. cerevisiae cells allows for a greater understanding of yeast tolerance to drugs, and aids in the development of more potent fungal infection medications.