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The influence of ionizing radiation on spore germination and emergent hyphal growth response reactions of microfungi

     Institute of Microbiology & Virology National Academy of Sciences of Ukraine, Kiev 25214, Ukraine

Victor Zheltonozhsky
Leonid Sadovnikov

     Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kiev 03028, Ukraine

John Dighton ¹

     Rutgers University Pinelands Field Station, New Lisbon, New Jersey 08064

The accident at the Chernobyl Atomic Energy Station resulted in radiation contamination of large tracts of land and particularly the reactor building itself. Sustained exposure of microfungi to radiation appears to have resulted in formerly unknown adaptive features, such as directed growth of fungi to sources of ionizing radiation. We evaluate here spore germination and subsequent emergent hyphal growth of microfungi in the presence of pure or mixed ß and radiation of fungi isolated from a range of long term background radiation levels. Conidiospore suspensions were exposed to collimated beams of radiation and percent spore germination and length of emergent hyphae were measured. All fungal species isolated from background radiation showed inhibition or no response in germination when irradiated. Isolates from sites with elevated radiation showed a stimulation in spore germination (69% mixed radiation and 46% for irradiation). Most isolates from low background radiation sites showed a significant reduced or no response to exposure to either source of radiation, whereas the stimulatory effect of experimental exposure to radiation appeared to increase in magnitude as prior exposure to radiation increased. We propose that the enhanced spore germination and hyphal growth seen in the exposure trials is induced by prior long term exposure to radiation and these factors could be important in controlling the decomposition of radionuclide-bearing resources in the environment.

Key words: hyphal growth, ionizing radiation, microfungi, spore germination