Fungi are all around in the environment. For example, the mold that invades wet basements, the mushrooms that we cook with, and the yeast that people use to make bread, wine, and beer are all members of the fungal kingdom. Fungi are also essential parts of natural ecosystems, breaking down complex carbon compounds like dead leaves or bark and returning nutrients to the soil. In addition to all this, many fungi are also extremely tolerant of polluted environments and can transform pollutants from highly toxic dissolved forms to less or non-toxic solid forms.
Between 2016 and 2018, as a postdoctoral fellow at the University of Minnesota, I led a small research team in an investigation of how common soil fungi responded to two environmental pollutants, manganese (Mn) and selenium (Se). Our study, published in the journal Environmental Science & Technology, was entitled, A fungal-mediated cryptic selenium cycle mediated by manganese biominerals. For our study we used two different species of fungi from the lab’s culture collection, a resource that contains microbes isolated from natural and polluted environments all over the US. Both elements investigated are micronutrients and important in small amounts, but can be harmful at high concentrations, such as in coal mine drainage where they are highly abundant.
We knew that under certain circumstances the fungi make biominerals, a subset of solid minerals formed through biological activity. So, we designed an experiment to track the fate of the pollutants during fungal growth. What we observed was that the fungi did, in fact, turn dissolved forms of our targeted elements into solid biominerals. Using a variety of geochemical techniques including a high-powered electron microscope, we identified manganese oxide and elemental selenium biominerals formed side-by-side, indicating that they can coexist in natural environments. The Mn oxides also seemed to recycle some of the Se back to dissolved forms, which is exciting because this transformation indicates there is a cryptic, or ‘hidden’ part of the natural Se cycle that was previously unknown. We are now working on follow-up engineering experiments using these same fungi to see if they can effectively remediate different types of contaminated wastewaters. We’re hopeful that these fungi can offer low-cost, low-input alternative remediation solutions for a wide variety of environmental clean-up applications. In the meantime, we’re also studying other biominerals that our fungi make and collecting new biomineral-forming fungi.
Carla Rosenfeld is the new Assistant Curator of Earth Sciences at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.
Rosenfeld, C.E, Sabuda, M.C., Hinkle, M.A.G., James, B.R., Santelli, C.M. A fungal mediated cryptic selenium cycle linked with manganese biominerals. Environmental Science and Technology 54(6): 3570-3580 doi:10.1021/acs.est.9b06022