The Chernobyl mushroom, known as Cladosporium sphaerospermumhas become one of the most fascinating protagonists of the area around the exploded reactor. For almost forty years, in fact, that area has remained inaccessible to humans, while some life forms seem not only to survive, but even to thrive.
Among them, this very black organism, anchored to the internal walls of one of the most radioactive buildings on the planet, continues to amaze researchers with a behavior that no one has yet fully understood.
How the Chernobyl fungus turned radioactivity into a possible biological advantage
When, at the end of the 1990s, a group led by microbiologist Nelli Zhdanova explored what remained of the shelter surrounding the destroyed reactor, they found themselves faced with an unexpected picture: 37 different species of fungi, many of which were characterized by a very dark pigment, melanin. Among all, Cladosporium sphaerospermum it was the most widespread and one of the most contaminated by radiation. From there began a scientific mystery that continues to this day.
Over time, another team — coordinated by Ekaterina Dadachova and Arturo Casadevall of the Albert Einstein College of Medicine — observed that this mushroom is not only not damaged by exposure to ionizing radiation, but even grows better when immersed in it. Totally counterintuitive behavior. In fact, ionizing radiation is powerful enough to shatter molecules and tear DNA: what for a human being is equivalent to a mortal threat seems to become, for this mushroom, almost a nutrient.
Precisely to explain this paradox, in 2008 Dadachova and Casadevall formulated a bold hypothesis: radiosynthesis. According to the theory, the melanin of the fungus would work in a similar way to the chlorophyll of plants, but instead of sunlight it would use ionizing radiation, transforming it into a form of energy useful for growth. At the same time, melanin would act as a protective shield, attenuating the most destructive effects of radiation.
Yet, none of this has been definitively proven. Evidence for any metabolic gain or radiation-fueled carbon fixation process is lacking. As Nilsaveresch, a Stanford engineer, pointed out, we are still far from identifying a true biological pathway that justifies the phenomenon.
The searches, however, did not stop. In 2022, one of the most surprising observations came from space: a sample of C. sphaerospermum was placed on the exterior of the International Space Station, under the violent rain of cosmic radiation. Sensors placed under the capsule detected less radiation passing through than fungus-free controls. While the study was not intended to investigate radiosynthesis, it confirmed another crucial quality: the potential use of the mushroom as a natural shield during future space missions.
The behavior, however, is not shared by all melanized species. Some mushrooms like Wangiella dermatitidis grow faster under exposure to rays, while others, like Cladosporium cladosporioidesincrease melanin production without showing superior development. In short, the case of C. sphaerospermum remains an intriguing exception.
And this brings us back to the central question: what is this fungus really doing inside one of the most dangerous areas on the planet? Is it using radiation to feed itself? Or is it an elaborate defense mechanism that only produces an indirect advantage? For now there are no definitive answers.
What we know, however, is evident: the Chernobyl fungus seems to have found an ingenious way to coexist with what represents an extreme danger for us, showing once again that life, when put under pressure, always finds a way to adapt.
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