Black fungus from Chernobyl: how melanin mold "eats" radiation and can protect people

In the zone where people have been allowed in protective suits and under dosimeters for decades, a black fungus lives peacefully, and it even seems to like it. Where we see deadly radiation, it sees a buffet - and that is why it has already caught the eye not only of microbiologists, but also of engineers who are thinking about how to protect people in space.

Back in the late 1990s, Ukrainian mycologist Nelly Zhdanova, working in the fourth power unit of the Chernobyl NPP, noticed thick black mold on the walls and cable channels, which not only survived, but, according to the results of the analysis, literally grew towards the radiation sources - a phenomenon called "radiotropism."^{1 2} Over the years, her team has described dozens of species of fungi in the exclusion zone, including particularly strange melanin-containing microorganisms like Cladosporium sphaerospermumwho felt at home in the reactor.^{1 3}

Further studies have shown that these black mushrooms are not only "attracted" to radiation, but also likely use it as a source of energy - a process conventionally called "radiosynthesis", by analogy with photosynthesis in plants.^{1 4} This discovery dramatically changed the idea of ​​the limits of sustainability of life on Earth and gave rise to a very practical question: if a mushroom is able to "eat" radiation in Chernobyl, can it become a human shield for people - from cleaning up contaminated areas to protecting astronauts from cosmic rays?^{2 5}

How a black fungus settled in the heart of a destroyed reactor

After the explosion on April 26, 1986, the fourth power unit of the Chernobyl NPP turned into one of the most radioactive places on the planet: colossal doses of iodine-131, cesium-137, and other radionuclides were released into the air and environment, and a 30-kilometer exclusion zone was created around the station, formally unsuitable for human life.^{1 6} But while people were evacuating, nature did what it does best: it gradually returned — from wolves and wild boars in the forests to microorganisms that even occupied the insides of the destroyed reactor.^{1 7}

When Zhdanova went inside the power unit structures in 1997, she discovered that black fungal growth was growing inside the protective metal cable boxes, on the walls and ceiling, and the hyphae of these fungi, according to laboratory studies, were growing in the direction of radioactive particles in the soil and structures.^{1 3} Additional analyses revealed that dozens of completely ordinary species of fungi live alongside these "radiosensitive" strains - that is, the Chernobyl mold is not the only life in the zone, but it is its behavior in a high radiation field that turned out to be the most paradoxical and interesting for science.^{1 3 8}

Melanin: a pigment that not only colors but also absorbs radiation

The key to the extraordinary resilience of Chernobyl mushrooms was the familiar pigment melanin, which gives skin, hair, and eyes a darker shade.^{1 4} It turned out that the cell walls of these microscopic reactor inhabitants are literally stuffed with melanin, which gives them their characteristic black color and probably protects against damage from ionizing radiation.^{1 4}

Melanin does not act as a metal shield that simply reflects particles; its chaotic structure "swallows" the radiation energy and dissipates it, while also acting as an antioxidant that neutralizes reactive particles generated by radiation in living tissues.^{1 4 9} In Chernobyl, this property is not only manifested in mushrooms: studies have shown that local frogs with darker skin, rich in melanin, have a higher chance of surviving and reproducing in contaminated bodies of water, and populations are gradually darkening - evolution in real time, but in a radiation setting.^{1 7 10}

Radiosynthesis: when a mushroom "photosynthesizes" with radiation

In 2007, researcher Ekaterina Dadachova and colleagues conducted a series of experiments where melanin-containing mushrooms were irradiated with cesium-137 and their growth was compared with control samples without radiation.^{1 4} It turned out that melanized mushrooms grew about 10% faster when exposed to radiation, and analysis showed changes in the electronic structure of melanin, which may indicate that radiation "recharges" their metabolism.^{1 4}

On this basis, scientists have put forward the hypothesis of "radiosynthesis" - the use of the energy of ionizing radiation to support metabolic processes, somewhat similar to photosynthesis in plants, which convert sunlight into chemical energy.^{1 4} The mechanism has not yet been definitively revealed: the search for specific proteins, metabolic pathways, and areas in the melanin structure that could directly convert radiation energy into something useful for the cell is ongoing, but the idea itself has seriously expanded the idea of ​​what life on the planet can "ride" on.^{1 4 9}

Space experiments: Chernobyl mushroom on the ISS

To test how the mysterious fungus behaves outside Earth, researchers sent an isolate Cladosporium sphaerospermum from the Chernobyl zone to the International Space Station in an experiment that lasted 26 days.^{1 5} Orbital samples exposed to galactic cosmic radiation grew on average about 1,2 times faster than control cultures on Earth, although scientists are careful to note that the result could be affected not only by the level of radiation, but also by microgravity.^{1 5}

In parallel, sensors were placed under the mushroom layer on the ISS to measure how much the thickness of the melanin biomass actually blocks cosmic radiation.^{1 5} It turned out that even a thin layer of mycelium reduced the level of recorded radiation compared to bare sensors, which gave reason to talk about the potential of mushrooms as a biological radiation shield - a "living wall" that grows on its own and does not require hundreds of tons of metal or water.^{1 5}

Why traditional radiation shields are bad friends with space

One of the main limitations for long-term flights to the Moon or Mars is cosmic radiation itself: streams of charged particles and galactic cosmic rays that can penetrate even lead screens and accumulate a dose dangerous to the health of astronauts.^{1 11} On Earth, we are protected by the atmosphere and magnetic field, but outside of them, people actually find themselves in a radiation "survival game," where every additional day increases the likelihood of cancer and other complications.^{1 11}

Classic materials for protection — water, polyethylene, special composites — perfectly shield part of the flow of charged particles, but have one "minor" drawback: they will have to be launched from Earth in huge quantities, and each kilogram of cargo in space costs as much as a good car.^{1 12} Metal and glass have a similar problem—they are heavy, expensive, and unable to repair themselves, unlike living systems that can potentially be grown on-site with minimal starting supplies.

Microarchitecture: When walls and furniture made of mushrooms are no joke

Against this backdrop, NASA and other space agencies are seriously looking at so-called mycoarchitecture — the use of fungi and mycelium as building materials for future bases on the Moon and Mars.^{1 12} Research at NASA Ames has shown that fungal mycelium can be grown in the form of panels, domes, or furniture using local resources (regolith, organic waste), and then stabilized, resulting in lightweight but fairly strong structures.^{1 12}

If you combine such fungal structures with melanin-containing species, like the Chernobyl one C. sphaerospermum, theoretically, it is possible to obtain not just an "ecohome" in space, but a self-healing shell that is both a supporting structure and an additional layer of radiation protection.^{1 5 12} The idea still sounds like a science fiction scenario, but the first experiments — from Chernobyl to the ISS — have already shown that, at least on a laboratory scale, the fungus is capable of working as a natural biological screen.

Not all black fungus is a "radio-eater", science is still arguing

Despite the exciting results of some studies, scientists emphasize that we should not romanticize all melanized mushrooms as universal "radiation eaters."^{1 4} Some experiments show radiotropism and enhanced growth in the radiation field only in some species, while other melanin-containing fungi demonstrate neither movement toward the source nor an increase in growth rate.^{1 8}

A 2006 study found that of 47 species of melanized fungi from the Chernobyl zone, only nine exhibited directional growth toward the caesium-137 source, while the others behaved neutrally.^{1 8} And modern experiments comparing melanin-containing and "regular" mushrooms under the influence of radiation sometimes found no difference in growth rates at all - which emphasizes that gamma radiation itself is not a magic fertilizer, and the role of melanin and other factors still needs to be analyzed in detail.^{1 9}

Possible applications on Earth: from bioremediation to personnel protection

In addition to space prospects, Chernobyl mushrooms can also be useful in more mundane tasks - cleaning up contaminated areas and protecting people who work with radiation sources.^{2 13} Hypothetically, specially grown melanin-containing biofilms or mushroom-based composites could be used as additional screens in environments with elevated radiation background or as part of radionuclide containment systems in waste repositories.^{2 13}

In parallel, researchers are discussing the possibility of using fungi for bioremediation — the gradual "removal" of radioactive particles from soil and water thanks to the ability of mycelium to accumulate and fix pollutants.^{2 13} It sounds attractive, but here, in addition to radiation, another factor arises - biosafety: everything that can accumulate radionuclides must then be safely collected and disposed of so as not to turn the "living filter" into another source of risk.

Scientific limitations: where excitement ends and sober assessment begins

The Chernobyl mushroom phenomenon is a great example of how the media loves strong formulas like "mushroom that eats radiation," while science itself moves much slower and more cautiously.^{1 4} Even supporters of the radiosynthesis theory admit that for now, this is a hypothesis that requires molecular evidence — the identification of specific "links" between the absorption of energy by melanin and its conversion into useful work by the cell.^{1 9}

Experiments in Chernobyl, laboratories, and on the ISS provide fragmentary, albeit impressive, data: somewhere mushrooms grow faster, somewhere they simply survive where other life forms would have already died, somewhere they actually shield some of the radiation.^{1 5 8} But the path from "interesting oddity" to industrial technology always goes through dozens of cycles of verification, scaling, and not the most romantic calculations of costs and risks.

Ukrainian context: when Chernobyl becomes a laboratory of the future

For Ukraine, this story is not only about amazing biology, but also about how a long-standing traumatic symbol — Chernobyl — is gradually transforming into a world-class scientific testing ground.^{1 7} It is from here that they take material for research into the adaptation of animals and plants to radiation, study the evolution of pigmentation in frogs, analyze the condition of forests and soils, and now they also export mushrooms for space experiments to the ISS.^{1 7 10}

Paradoxically, but it is a fact: in a country that simultaneously experienced the largest nuclear accident of the 20th century and a full-scale invasion, it is the Chernobyl landscape that can provide the keys to the technologies of the future — from new types of biosecurity to models of ecosystem resilience in extreme conditions.^{1 2} And if some organisms are capable of turning radiation hell into a living environment, there's a chance that humanity could borrow a few tricks from them — preferably without turning into a mushroom entirely.

Sources

1. BBC Future: "The mysterious black fungus from Chernobyl that may eat radiation"
2. Zhdanova et al.: Field studies of fungi in the Chernobyl NPP zone and description of the phenomenon of radiotropism
3. Microbiological journals: publications on the species diversity of fungi in the Chernobyl Exclusion Zone
4. Dadachova E. et al.: experiments with melanin-containing fungi and the radiosynthesis hypothesis
5. Frontiers in Microbiology: research Cladosporium sphaerospermum on the ISS and assessment of its radioprotective properties
6. IAEA and scientific reviews: materials on the scale of radiation contamination due to the Chernobyl accident
7. The Conversation and other popular science platforms: articles about evolutionary changes in the fauna of the Chernobyl zone, in particular "black frogs"
8. International Journals of Radioecology: Papers on Melanized Fungi and Limitations of the Radiotropism Phenomenon
9. Reviews in the biophysics of melanin: studies of its ability to absorb and scatter radiation energy
10. NASA and ESA: materials on space radiation, risks to astronauts and concepts of bioshields and microarchitecture
11. Space Medicine Publications: Assessment of the Impact of Galactic Cosmic Radiation on the Health of Deep Space Mission Crews
12. NASA Ames Engineering Research: Microarchitecture Projects, Fungal Structures, and Potential Combinations with Fungal Radioprotective Properties
13. Bioremediation articles: analysis of the prospects for using fungi to clean up radioactively contaminated areas