In the years after the 1986 explosion at Chernobyl, scientists lowering cameras and robots into the ruins of Reactor No. 4 found something growing where almost nothing should: dark, sooty films of fungus, spreading across walls and debris that were soaked in enough radiation to kill a person in minutes. Not clinging on at the edges, barely surviving. Thriving — in one of the most radioactive places humans have ever made.
That part is not folklore or hype. Melanin-rich "black fungi" really do colonize the contaminated zone, and really do grow well there. Established The question this issue is about — the one the internet usually races past — is why: are these fungi simply tougher than radiation, or are they somehow living off it?
A census of the dead zone
Over roughly fifteen years of sampling in and around the plant, researchers isolated about 2,000 strains — some 200 species across nearly 100 genera — from Chernobyl's soils, surfaces, and even the cooling waters. Established A striking share of them were melanized: dark-pigmented fungi loaded with the same broad family of pigment that colors human skin. Some were found growing into the radioactive graphite and "hot particles" thrown out by the reactor, slowly breaking them down. Established
The reason these particular fungi can shrug off such doses is reasonably well understood. Melanized fungi are remarkably radioresistant — surviving radiation thousands of times higher than the doses that would sterilize most life. Established Melanin is a dense, dark pigment that physically absorbs radiation and mops up the destructive free radicals that radiation tears loose inside a cell. Established In other words, melanin is good armor. Everyone agrees on the armor. The argument is about whether it's also a solar panel.
The threads lean in
Here is the first genuinely odd finding. Several of the Chernobyl fungi don't just tolerate radiation — they grow toward it.
For a long time that was a soft observation, easy to explain away: fungi creep toward the radioactive graphite, sure, but maybe they're just chasing the carbon in the graphite, which fungi love to eat. So in a careful 2004 study, a team built setups that stripped the carbon out of the equation, exposing fungal spores and their growing threads to pure directional sources of beta and gamma radiation. The hyphae still bent toward the radiation. Established They named the effect radiotropism — growth steered by radiation itself.
That much is solid: the attraction is real, and it isn't just the fungi following a food smell. Established What the same study was careful to say — and what tends to get dropped in the retelling — is that they could not identify the biological mechanism behind it. Contested The fungi lean toward the source. Nobody has shown exactly how, or why, they "know" to.
The bold claim: "radiosynthesis"
Now the part that launched a thousand headlines. In 2007, a group at the Albert Einstein College of Medicine ran lab experiments on three melanized fungi — including Cladosporium sphaerospermum, one of the Chernobyl colonists. Grown under radiation around 500 times higher than the normal background, the melanized fungi put on biomass faster than they did without it. Preliminary The researchers also showed that irradiation changed the electronic properties of melanin and boosted its ability to shuttle electrons (measured as a three- to four-fold jump in a melanin-driven chemical reaction). Preliminary
From this they floated a genuinely thrilling idea: maybe melanin can act like chlorophyll does for plants — not capturing sunlight, but capturing ionizing radiation and channeling its energy into the fungus. They called the proposed process radiosynthesis: a third way to make a living, alongside photosynthesis and chemosynthesis. A fungus powered by radiation. It's a beautiful hypothesis. And it's worth being precise about exactly how far the evidence carries it.
Where we get honest
"This fungus eats radiation" is the version that travels. It is not what has been demonstrated.
What the experiments show is that melanized fungi can grow better under certain radiation, and that radiation changes melanin's chemistry. Preliminary What they have not shown is the thing the word "radiosynthesis" promises: a measured energy-harvesting pathway, radiation-driven carbon fixation, a clear accounting of energy in and growth out. Contested There's a quieter explanation that the data can't rule out. In those experiments the fungi were still fed ordinary nutrients — so the growth boost might not be the fungus burning radiation for fuel at all, but rather radiation (or melanin's response to it) helping the cells use their normal food more efficiently, or simply protecting them so they grow with less damage. Critics who have gone back through the work argue the energy actually deposited was too small, and the nutrients in the dish too sufficient, to call this feeding on radiation. Contested Even the idea's own champions, in their reviews, land on "melanin may help the fungus capture radiation energy — but more evidence is needed." That's an honest place to be. It is not "confirmed."
So hold two things at once. The established marvel: a whole guild of fungi flourishes in lethal radiation and steers its growth toward the source — armored by melanin, genuinely radiotropic, decomposing reactor graphite. The unproven dream: that they run on the radiation like a plant runs on the sun. The first is real and astonishing. The second is a hypothesis with suggestive lab hints and no closed case — exactly the kind of "we don't know yet" this kingdom keeps handing us. Contested
A footnote from orbit
One reason the idea won't die is that it might be useful even if "radiosynthesis" never pans out — because the armor alone is valuable. In 2018–2019, a thin lawn of Cladosporium sphaerospermum was grown on the International Space Station for 30 days to test whether living, self-repairing fungus could blunt cosmic radiation, a headache for any trip to Mars. A layer only about 1.7 mm thick measurably lowered the radiation passing through it — by roughly 2% versus the control — and the fungus grew about a fifth faster in space than the ground sample. Preliminary That's a single small experiment, and a 2% dent is modest. But a radiation shield that grows itself and heals its own scratches is the kind of beautifully strange idea this fungus keeps inspiring — whether or not it ever truly eats the thing it's shielding you from.
Next in the Bestiary: a fungus that turns itself to ink — the inky caps that dissolve their own caps into black liquid to spread their spores. See you there.