DISSERTATION RESEARCH: Molecular Evolution of Extracellular Hemoglobins in the Vestimentiferan Tubeworm Ridgeia piscesae

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The tubeworm Ridgeia piscesae of the hydrothermal vents in the northeast Pacific Ocean uses extracellular hemoglobins to deliver environmental sulfide to intracellular bacteria, which in turn uses sulfide to create sugars for the host. R. piscesae displays several different growth forms depending on the temperature and chemistry of vent fluids. The growth forms of R. piscesae are genetically identical, but why R. piscesae shows variation in body shape in different environments is a mystery. This research will characterize sequence diversity and gene expression differences of hemoglobin subunits in two R. piscesae growth forms to determine if this candidate molecule responds to environmental variation in sulfide levels. Mapping the location of globin genes within the tubeworm genome will provide a better understanding of how these genes are regulated.Hydrothermal vents are unique environments on this planet because organisms use chemical energy rather than sunlight drives the ecosystem. Genetic studies of Ridgeia piscesae will provide more insight into how organisms adapt to extreme environments. This research will provide a unique opportunity to learn if gene expression is influenced by the environment. Elucidating patterns of DNA sequence variation in globin genes will also increase our understanding of how environments influence patterns of evolution.