Conley, Bridget2022-01-042022-01-042021-10https://hdl.handle.net/11299/225908University of Minnesota Ph.D. dissertation. October 2021. Major: Microbiology, Immunology and Cancer Biology. Advisor: Jeffrey Gralnick. 1 computer file (PDF); vi, 166 pages.While many metabolisms make use of soluble, cell-permeable substrates like oxygen or hydrogen, there are other energy-yielding sources, like iron or manganese, that cannot be brought into the cell. Some bacteria and archaea have evolved the means to directly "plug in" to these valuable energy sources in a process known as extracellular electron transfer (EET), making them powerful agents of biogeochemical change and promising vehicles for bioremediation and alternative energy. The diversity and distribution of EET is poorly understood and the molecular mechanism has primarily been studied in two model systems, Shewanella oneidensis and Geobacter sulfurreducens. The following thesis presents evidence for the mechanism of EET in Aeromonas hydrophila and Vibrio natriegens, which enhances survival in fermentative conditions for V. natriegens. The genes encoding mtrCAB are present in a broad diversity of bacteria found in a wide range of environments, emphasizing the ubiquity and potential impact of EET in our biosphere.enThesis or Dissertation