None is like the other: the interaction of selected fungi with radionuclides

Not only since Chernobyl and Fukushima is it well known that fungi can accumulate large amounts of heavy metals and radionuclides. Although there are many publications describing this phenomenon and naming transfer factors, almost nothing is known about the underlying molecular processes being responsible for the binding, uptake and accumulation in the cell or even transport inside the organism for elements like uranium, americium and other heavy radio-metals. However, knowing this is crucial if one wants to understand the influence of fungi on the migration behavior of radionuclides in the environment. It is all the more important to know the underlying biochemical processes and to know how environmental influences affect the radionuclide-cell interaction, if one considers using these extraordinary properties to biologically immobilize radionuclides in contaminated soil or even to remove radionuclides from it. As part of the BioVeStRa project, various fungi have been studied to determine their potential for precautionary radiation protection and the remediation of contaminated soils. Therefore, two fungi were selected based on published transfer factor and a known rapid growth on complex media, namely Schizophyllum commune and Leucoagaricus naucinus. Additionally, two further fungi metabolically related to S. commune or L. naucinus were included also in the studies to determine if similar fungi behave similarly or not. To study the fungi, a combination of growth and binding experiments, mass spectrometry, fluorescence spectroscopy and electron microscopy was used. In summary, it can be stated, that S. commune is not only the most robust fungus that prevails even in the test field against autochthonic soil microbes and fungi, but also shows the highest accumulation rates for uranium and europium, the latter as a substitute for trivalent actinides such as americium. Furthermore, it could be shown that fungi behave very differently depending on the investigated elements.