Extreme Radiation Microbiology
A few years after the accident in Chernobyl, black spots were observed in and around the nuclear power plant, looking like those sometimes found on shower curtains. Ekaterina Dadachova and her colleagues at the Albert Einstein College of Medicine in New York studied the fungi, identified as Cladosporium sphaerospermum, Wangiella dermatitidis, and Cryptococcus neoformans. These fungi can grow in an environment where the radiation level is 500 times higher than in the normal environment. Under exposure to radiation, they start producing melanin, the same pigment as in human skin. In the same way as some organisms use the pigment chlorophyll to convert the energy from light into chemical energy, a reaction known as photosynthesis, those fungi perform radiosynthesis, using melanin to convert the energy from X or gamma radiation into chemical energy. Ionizing radiation seem to change the electronic properties of melanin. In environments normally considered hostile to life, the growth and germination of melanized fungal cells is greater than non-melanized cells.
It has been suggested that these radiotrophic fungi could be employed to protect astronauts from radiation during space exploration missions or stays on the moon or Mars. Up-mass restrictions require innovative solutions for radiation shields.
Petri dishes containing Cladosporium sphaerospermum were sent to the International Space Station by NASA and placed in conditions analog to habitation on the surface of Mars. Results from the study indicate that a layer of the fungus only 1.7-millimeters thick absorbed about 2 percent of the cosmic radiation. It thus appears possible that radiation protection could be provided by cultivation of the radiotrophic fungi mixed with regolith, the soil powder found on the moon and on the red planet. The fungi might also be used to contribute to the food supply.
First published by iia Sept 2020