Objectives: The aims of this project were to 1) investigate whether certain melanin-producing fungi demonstrate increased growth in response to varying radiation levels (this is called radiosynthesis) and 2) to test the ability of the fungi to shield radiation.
Methods: Cladosporium cladosporioides was grown in broth medium and on agar plates, both inoculated with or without p-coumarin (an inhibitor of melanin synthesis). Testing groups were exposed to varying doses of radiation from an X-ray machine several times over a 2-week period. X-ray images of the plates were also recorded to estimate radiodensity. Total growth in the broth cultures was measured by dry weight at the end of the experiment.
Results: There was a visible reduction of melanin expression in the broth cultures inoculated with p-coumarin. Dry weight measurements are currently underway for the broth to determine which group produced more biomass. On agar plates, p-coumarin did not appear to affect the development of melanin, though the fungal colonies may have grown more slowly in the presence of p-coumarin. Statistical analysis of the X-ray images is underway and may reveal differences in radiodensity.
Conclusions: These experiments do not conclusively support or refute the hypothesis that Cladosporium cladosporioides is able to harness ionizing radiation for cellular energy. The cultures could have been pulling energy from the growth medium for cell repair and not producing it via radiosynthesis; data collection may change this conclusion. The p-coumarin plate’s failure to inhibit melanin growth means conclusions about radio shielding effects of melanin cannot be drawn.