Genetic Mechanisms of Selenium Resistance in Fungi

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The Ohio State University

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Microbial communities have important effects on nutrient levels and contamination within soils. Both fungi and bacteria are present in soils that contain significantly high concentrations of selenium. Polluted soils contaminated with selenium cause stress for organisms living in these communities. Fungi respond to this environmental stressor through mechanisms that have not been studied previously. Various species of bacteria are known to reduce selenate and selenite to elemental selenium. Several selenium reduction genes have been identified in bacteria, but less is known about fungal selenium tolerance. I hypothesized that fungi would show tolerance to selenium, and this will vary based on selenium content of the soil site. Additionally, I hypothesized that fungi will also employ genetic mechanisms to process selenium. A library of fungal isolates was collected from paired high and low concentration selenium sites located in the Western Rocky Mountain region. Each isolate was grown on PDA-V8 agar plates with increasing concentrations of selenate ranging from 0 ppm to 500 ppm. Fungal colony size was measured for each sample. We have defined the community composition of the fungi in our sites. Analysis of fungi from our library showed variation in tolerance across sites. Our data suggests that fungi are able to utilize two mechanisms to tolerate high levels of selenium. Adapted fungi showed constant or increasing growth with increasing selenium concentrations. Non-adapted fungi showed decreasing growth with increasing selenium concentrations. Adapted fungi are likely able to metabolize selenium efficiently. Additionally, previous selenium exposure within the sample sites affected the tolerance strategies present. Further study is needed to investigate the details of the mechanisms suggested by our results. More research is required to fully understand the effect of selenium on microbial communities and how they respond to stress.



fungi, selenium, microbes, stress