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dc.contributor.advisor Dietrich, Fred S. en_US
dc.contributor.author Diezmann, Stephanie en_US
dc.date.accessioned 2009-05-01T18:34:50Z
dc.date.available 2009-05-01T18:34:50Z
dc.date.issued 2009 en_US
dc.identifier.uri http://hdl.handle.net/10161/1187
dc.description Dissertation en_US
dc.description.abstract <p>Hydrogen peroxide is used by animals and plants to deter the growth of microbial invaders by inflicting DNA lesions, protein oxidation and lipid membrane modifications. Pathogens protect themselves with enzymes and scavenging proteins. This study investigated population genetic, biochemical and genetic aspects of peroxide survival in <i>Saccharomyces cerevisiae </i> to address its importance for yeast biology and fungal pathogenicity.</p><p>Population genetic analyses of DNA sequences from five loci from 103 strains encompassing the known ecological spectrum of <i>S. cerevisiae</i> show that it is a recombining species with three divergent subgroups, which are associated with soil, fruit, and vineyards. Clinical isolates cluster with fruit isolates but are significantly more resistant to peroxide. Clinical isolates are genetically diverse, indicating multiple origins of the pathogenic lifestyle and eliminating the possibility that peroxide resistance is due to shared ancestry rather than it's importance for than its importance in colonizing the host.</p><p>Biochemical aspects of peroxide survival were studied in a resistant (high-survival) clinical isolate, a sensitive (low-survival) laboratory strain and their hybrid. Catalase activity and expression levels are indistinguishable among strains. Co-culture assays and growth curve records indicate that a secreted factor improves survival of the laboratory strain and that the phenotypic difference is most pronounced during exponential growth, excluding mechanisms of the General Stress Response effective during stationary phase. Semi-quantitative expression profiles of stress response candidate genes do not differ, suggesting a novel resistance mechanism.</p><p>To elucidate the genetic basis of peroxide survival, the hybrid was sporulated and 200 F1 segregants phenotyped and genotyped for oxidative stress candidate genes. Peroxide survival is a dominant quantitative trait and not linked to catalase, peroxidase or superoxide dismutase genes. 1,246 backcross segregants were phenotyped and 93 segregants selectively genotyped using microarrays. A 14-gene locus on chromosome XVI displayed marker-trait association. One gene, <i>RDS2</i>, encodes a zinc cluster protein acting as a regulator of drug sensitivity and contains a non-synonymous polymorphism whose exchange between the parental strains results a 15% decrease in survival in the clinical strain.</p><p>This work establishes a novel function for <i>RDS2</i> in oxidative stress response and demonstrates the effect a quantitative trait nucleotide has on a clinically relevant phenotype.</p> en_US
dc.format.extent 2266470 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject Biology, Genetics en_US
dc.subject Biology, Microbiology en_US
dc.subject Evolution en_US
dc.subject Oxidative Stress en_US
dc.subject Quantitative Genetics en_US
dc.subject Saccharomyces cerevisiae en_US
dc.title Evolutionary Implications and Genetic Basis of Peroxide Survival in Saccharomyces Cerevisiae en_US
dc.type Dissertation en_US
dc.department Genetics and Genomics en_US
duke.embargo.months 12 en_US
dc.date.accessible 2010-05-18T05:00:34Z

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