Sabuda, Mary2021-09-242021-09-242021-07https://hdl.handle.net/11299/224560University of Minnesota Ph.D. dissertation. July 2021. Major: Earth Sciences. Advisor: Cara Santelli. 1 computer file (PDF); vi, 357 pages + 5 supplementary files.Selenium (Se) is both a micronutrient required for most life and an element of environmental concern due to its toxicity in high concentrations. Se can be released into the environment through both natural and anthropogenic (human) activity, where it can exist as volatile or organic Se(-II), nanoparticulate Se(0), or aqueous Se(+IV/VI). Coal mining, processing, and burning can release high levels of Se to the environment, as selenium can easily substitute for sulfur, a main component of coal. Se is also useful in the medical field, where it has anticancer properties and Se(0) is an effective coating on medical devices. While most knowledge of biotic Se transformations is related to either anaerobic or aerobic bacterial processes, some common soil Ascomycota fungi can reduce Se under oxic conditions. These microeukaryotes readily transform elevated concentrations of this essential toxin from a bioavailable aqueous phase (Se(IV/VI)) to solid or volatile phases (Se(0/-II)), which is ideal for engineering efficient, cost-effective treatment strategies for Se-contaminated environments. Elucidating the geochemical and genetic mechanisms behind filamentous fungal Se transformation strategies will progress biotechnological applications for biogenic Se nanoparticles, and aid in a more complete understanding of Se biogeochemical cycling.enBioremediationFungiGeochemistrySeleniteSeleniumTranscriptomicsThesis or Dissertation