When scientists first studied the remains of the Chernobyl Nuclear Power Plant, they discovered something unexpected: dark-colored fungi colonizing the reactor walls. And these weren’t just normal fungi toughing it out in a harsh environment - samples taken directly from the reactor environment not only tolerated the radiation but grew toward the radiation source, in behavior reminiscent of phototropism in plants.
Cladosporium sphaerospermum - The University of Adelaida
These fungi contain high amounts of melanin - the same pigment that gives human skin its dark color to protect it from intense sunlight. In these organisms, however, melanin serves a different function. Lab experiments have shown that when exposed to higher levels of ionizing radiation, the fungi actually grow faster. This happens because melanin converts radiation into usable energy. Although radiation doesn’t replace these fungi's need for organic nutrients, it effectively enhances their growth.
This way of getting energy was unlike anything scientists had seen in nature before. The known strategies were plants and algae using light, animals and fungi consuming organic matter, and certain bacteria using chemical reactions. The Chernobyl fungi didn’t fit into any of those categories. Researchers proposed the term radiotrophs for organisms that are able to use radiation as an energy source.
This has sparked interest in engineering - researchers are testing whether radiotrophic fungi could be used for radiation shielding. Early experiments have shown that layers of these fungi can reduce radiation exposure beneath them. That could be useful not only for cleanup efforts at nuclear sites, but potentially for protecting astronauts on long-duration missions.