A fungus found in the Chernobyl reactor is radiotropic. It turns out that it feeds on dangerous radioactive radiation.
Researchers ventured with a remote-controlled robot into the exploded reactor of Chernobyl. They found something strange. A black mold covered the cooling basins. The researchers took samples of the fungi and continued the cultivation.  They found something amazing. In their experimental set-ups, where the fungi were exposed to radioactivity, this was found not to hinder their growth, but rather to promote it considerably. Apparently the fungi felt very comfortable under the dangerous radiation. And possibly used it as an energy source. Like plants use sunlight. Radiotrophy became the name for this new, still unknown phenomenon.
What is Radiotrophy?
Radioactivity kills, we learn at school. With the 'radium girls' painting the new luminous wonder material on dials, it ended badly. But this does not apply to all beings. There are fungi that thrive on radiation. Such as fast electrons, but also other radiation. Plants only live on sunlight. They use blue and red light, the so-called photosynthetically active radiation or PAR. This is about half of all solar radiation. Green is an unusable wavelength for plants. That explains why plants are usually green.
But radiotrophic organisms, we think, use a simple, robust system. Their secret: the black dye melanin, which is also found in colored skin. Ionizing radioactive radiation tears melanin apart or changes the configuration of their electrons. During the process where these molecules recover, NADH is released, which the fungus uses as an energy source for the metabolism. Simple, not very efficient, but very robust. For example, they can handle much more different, and also much more dangerous, types of radiation than plants. That is why melanin is also black. It really absorbs all light.
It makes these fungi tough survivors, surviving even in exposed areas of spaceships. They don't ask for much. Water, a carbon source, temperatures at which liquid water occurs. And a lot of radiation, so. Some of these species make you sick. Here their toughness is a problem.
New domains for radiotrophic life
It also shows that life is much tougher than many people realize. And that environments that are too dangerous for us can also be a paradise for other life forms. Such as radiotrophic fungi. There are places in the universe that are very rich in radioactive radiation. Like in a planetary system that forms after a supernova. Or planets, such as early Earth, where the remains of an exploded star dumped a shower of radioactive material into the biosphere.
Or think of Jupiter's moons. The highly active magnetic field of Jupiter is constantly bombarding the surface of the great icy moons Ganymede, Callisto and Europa with ions. For us this is deadly. But a fungus like Crytococcus neoformans or Wangiella dermatitidis, which of course must be adapted to the harsh conditions and low temperatures of these icy moons, probably 'thinks' otherwise. There may be radioactive planets , roaming the universe, whose inhabitants have never seen a sun. And animals feed on radiotrophic fungi instead of plants.
- E. Dadachova and A. Casadevall, Ionizing Radiation: how fungi cope, adapt, and exploit with the help of melanin, Curr Opin Microbiol, 2008, DOI 10.1016 / j.mib.2008.09.013
- Katherine Kornei, No star, no problem: Radioactivity could make otherwise frozen planets habitable, Science Magazine, 2020, DOI: 10.1126 / science.abc0189