Investigating the Chemistry and Biophysics of UV-Resistance in Dark-Pigmented Fungi

Many species of fungi have been found growing in environments with high exposure to ultraviolet radiation. Not much is known about how fungi survive in such conditions, and there are implications for application of these mechanisms for use in spacecraft. This project seeks to investigate the chemical and biophysical basis of UV tolerance in dark-pigmented fungi. Fungi were selected to test based on suspected production of melanin and previous isolation from Peavy Hall on the OSU campus and were then tested for a UV tolerance threshold via increasingly intense exposures to UV light followed by bioassays to test mycelial growth. Fungi were also tested under different growing conditions to identify methods for increased melanization. Melanin was extracted from Epicoccum sorghinium and mixed with pullulan, a natural fungal polysaccharide, to create a UV-resistant film, which was then applied to fungi under the lethal threshold to test for increased survival. The lethal threshold for the fungi was found to be at about 3,600μW/cm2 with a wavelength of roughly 212 nanometers and exposure times of 24 to 48 hours. Two concentrations of copper mixed with agar was found to darken the biomass for several species, and no definitive results were found for the melanin-based protective coating. Such a high lethal threshold implies very strong mechanisms for UV tolerance in these fungi, and future studies should be done to establish more precise thresholds for more species and to examine the biochemistry of their UV tolerance.