DISSERTATION RESEARCH: The Genetic Basis of Adaptation in Thermally Adapted Escherichia Coli

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DISSERTATION RESEARCH: The Genetic Basis of Adaptation in Thermally Adapted Escherichia ColiAlbert Bennett and Michelle RiehleThis project will take a genomic approach to understanding of adaptation to high temperature. The PIs will examine populations of Escherichia coli, a microbe present in the intestinal flora of all mammals, that have been cultured in the laboratory for 2000 generations at high temperature. They will examine the genetic basis of adaptation to high temperature, the degree of parallel evolution among different lines adapted to high temperature, and the reversability phenotypic and genetic changes upon exposure of populations to lower temperatures. The work addresses three main goals. The first goal is to examine how adaptation to high temperature changes the copy number of genes, either increasing copy number via duplication or decreasing copy number via deletion. The second goal is to examine how adaptation to temperature affects the level of gene expression. Lastly, given changing thermal conditions, how do organisms respond on the phenotypic or organismal level and how do they respond on the genetic level? Is there a particular pattern? Are changes at the organismal level always caused by the same genetic change, or can multiple genetic changes yield the same change in phenotype? DNA high-density arrays will be used to screen whole genomes for regions of gene duplication and deletion, and to characterize gene expression. This whole genome approach is a powerful tool in that it allows the simultaneous screening of all 4290 E. coli genes, making individual examination of all 4290 genes unnecessary. This work is important because it begins to dissect the complex process of adaptation that has intrigued comparative and evolutionary biologists ever since the time of Darwin.