Radionuclides and Fungi: Fungal Behavior, Fungal Communities and Fungal Impacts on Radionuclide Mobility in Soil.
John Dighton1, Tatyana Tugay2, Nelli Zhdanova2, and Victor Zheltonozhsky3. (1) Rutgers Pinelands Field Station, Po Box 206, 501 Four Mile Road, New Lisbon, NJ 08064, (2) Institute of Microbiology and Virology, Zabolotny St 154, Kiev, 252143, Ukraine, (3) The Instiute for Nuclear Research, National Academy of Sciences of the Ukraine, Kiev, Ukraine
Following the Chernobyl nuclear reactor accident, the interactions between radionuclides and fungi in ecosystems have been studied from the point of view of effects of radionuclides on fungal community structure and the influence of fungi in regulating movement of radionuclides in soil. Our presentation will provide a summary of three aspects of fungal/radionuclide interactions. First, we show that radionuclides directly, or through the production of secondary emissions, can significantly influence spore germination and fungal hyphal growth (fungal behavior). Using collimated sources of gamma and combined beta and gamma radiation we have shown that the presence of ionizing radiation significantly enhances conidiospore germination and stimulates emergent hyphal growth in isolates that have been derived from previously radionuclide contaminated areas. Fungal isolates from uncontaminated sites either show no response to applied radiation of are suppressed. In a similar fashion we present evidence that fungal isolates from contaminated soil and the walls of the destroyed reactor room experiencing long term chronic doses of radiation show directed growth of their emergent hyphae towards collimated sources of beta, gamma and combined ionizing radiation. These fungal behaviors are suspected to be induced by the long-term exposure to radiation and growth responses may be related to the possession of fungal pigments, which may also be important determinant of radionuclide resistance. Secondly, we show how the presence of hyphal pigmentation may be important in protecting the mycelium from radionuclide damage, thus resulting in changes of soil fungal communities to contain dominantly pigmented forms in the presence of high levels of radiation. The structure of fungal communities may, therefore, be dictated by radioresistance and have a subsequent impact on the ecosystem services provided by that community. Finally, a review of our own and other research will show the importance of basidiomycete fungal species, and, in particular ectomycorrhizal fungal species, in the uptake of radionuclides from contaminated sites. Evidence suggests that radionuclide immobilization in fungal biomass may be rapid and of long duration. Given that some radionuclides are preferentially translocated to fruiting structures (mushrooms) these fungi may not only be involved in long-term immobilization of radionuclides, but harvesting of mushrooms may be a potential method of site remediation.