CAREER: Genome-enabled investigations into the mechanisms and ecological controls on selenium transformations by fungi

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Selenium (Se), sometimes referred to as "the essential toxin", plays an important role in human and ecosystem health. Selenium is a required micronutrient for most living organisms. At elevated concentrations, however, Se is a toxic element of increasing environmental concern. Selenium bioavailability and toxicity largely depends on the form, or oxidation state, of the compound. Microorganisms, including fungi, play an important role in controlling and transforming Se chemical speciation by promoting a variety of chemical reactions. The processes by which fungi promote Se transformations, however, are largely unresolved, thus limiting knowledge of their specific contributions in nature. Using a genome-enabled approach, this research will examine and resolve the relevant fungal biogeochemical processes that transform Se speciation and ultimately influence the fate and distribution of selenium in nature. Results from the proposed research will also directly inform new technologies for Se bioremediation and will be of additional interest to government and local stake-holders who are regulating or managing Se issues. Through formal student training and engagement in public science communication in collaboration with local museums, this project will further engage, inform, and inspire students and the public on the important role that microorganisms play in maintaining and improving the overall health of planet Earth. To better understand the impact of fungi on biogeochemical processes that influence the fate of selenium in nature, this research will illuminate the currently unresolved molecular mechanisms and pathways that contribute to the aerobic reductive transformation of soluble, toxic Se oxyanions (selenate and selenite) to insoluble Se(0) and organic, volatile Se(-II) compounds by a diverse suite of environmentally-relevant Ascomycete fungi. The specific research objectives are to (1) identify the fungal mechanisms of selenate and selenite reduction in oxic environments, (2) assess the effects of key nutrients and trace metals on fungal Se transformation mechanisms and reaction products, and (3) investigate particle size, morphology, and structure of Se biomineralization products with respect to fungal growth conditions and Se reduction pathway. The genome-enabled approach will elucidate the genes and proteins that contribute to Se reduction by linking their expression to specific functions and resulting Se biominerals and organoselenium compounds. This approach will lead to the development of gene regulatory networks for these common fungal species, which will be highly beneficial for predicting the effect of environmental or biological change on Se speciation and will further benefit the advancement of fungal research in environmental and biological sciences. This project is jointly funded by the Geobiology and Low-Temperature Geochemistry Program in the Division of Earth Sciences and the Systems and Synthetic Biology Cluster in the Division of Molecular and Cellular Biosciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.