Date of Graduation
Eberly College of Arts and Sciences
Charles Joel McManus
The chemical 4-methylcyclohexanemethanol (MCHM) spilled in the Elk River near Charleston, WV in January 2014, impacting the drinking water of 300,000 residents. Initial studies on MCHM following the spill attempted to characterize its toxicological effects in animals, but largely ignored characterization of its effects on cellular pathways and metabolism. In this study, I used this chemical as a novel stressor for the model eukaryote S. cerevisiae to explore the relationship of genotype and stress phenotypes. Initial exploration characterized the stress phenotype of MCHM in yeast through growth assays, cell cycle analysis, and transcriptomic data. MCHM exposure caused cells to arrest growth in G1, activating a well characterized yeast process called the environmental stress response. Further exploration was carried out using a genetic screen of approximately 5000 haploid gene knockout strains, which combined with the transcriptomic data, revealed that the causes of the stress response in yeast were nutrient deprivation related to amino acid biosynthesis and reactive oxygen species production. A QTL analysis of standing variation between two parental strains with variable resistance uncovered the role of zinc homeostasis and its interaction with the hydrotrope chemical properties of MCHM in protein aggregation as a contributor to resistant phenotypes. Finally, an In-Lab evolution study to produce resistant strains for variant analysis showed mutations in the pleiotropic drug response transcription factor PDR3 cause a reproducible induction of MCHM resistance. These studies combined to characterize cellular changes from MCHM, identify genes required for tolerance, and explore both standing and evolved variation in genotypes that contribute to and produce an MCHM resistant phenotype.
Ayers, Michael C., "The role of genotype in Saccharomyces cerevisiae resistance to 4-methylcyclohexanemethanol" (2020). Graduate Theses, Dissertations, and Problem Reports. 7935.