Chernobyl Fungus Appears to Have Evolved an Incredible Ability : ScienceAlert

The Chernobyl Exclusion Zone may be off-limits to humans, but ever since the Unit Four reactor at the Chernobyl Nuclear Power Plant exploded nearly 40 years ago, other forms of life have not only moved in there, but appear to have survived, adapted and thrived.

Part of this may be a lack of humans… but for one organism, at least, the ionizing radiation present inside the structures surrounding the reactor may be an advantage.

There, clinging to the interior walls of one of the most radioactive buildings on Earth, scientists have found a strange black fungus that is curiously living its best life.

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it is called fungus Cladosporium sphaerospermumAnd some scientists think that its dark color – melanin – may allow it to use ionizing radiation through a process similar to the way plants use light for photosynthesis. This proposed mechanism is also called radiosynthesis,

but here’s the really funny thing C. sphaerospermum: Although scientists have shown that fungi thrive in the presence of ionizing radiation, no one has been able to figure out how or why. Radiosynthesis is a theory that is difficult to prove.

The mystery began in the late 1990s, when a team led by microbiologist Nelly Zhdanova of the Ukrainian National Academy of Sciences began a field survey in the Chernobyl exclusion zone to find out what life, if any, could be found in the shelter around the ruined reactor.

There, they were stunned to find an entire community of fungi, documenting an astonishing 37 species. Specifically, these organisms are dark to black in color, rich in the pigment melanin.

C. sphaerospermum Dominated the samples, also displaying some of the highest levels of radioactive contamination.

As surprising as this discovery was, what happened next deepened the intrigue.

Radiopharmacologist Ekaterina Dadachova and immunologist Arturo Casadevall – with both posts Albert Einstein College of Medicine in the US – led a team of scientists who revealed C. sphaerospermum Ionizing radiation does not harm fungi the way it does other organisms.

Ionizing radiation describes the emission of particles that are powerful enough to knock electrons out of atoms and convert them into their ionic forms.

This sounds great on paper, but in practice, ionization can tear molecules apart, interfere with biochemical reactions, and even cause DNA to fragment. Neither of these are good for humans, although it can be used to destroy cancer cells, which are particularly sensitive to its effects.

However, C. sphaerospermum Seemed strangely resistant and got even better when bathed in ionizing radiation. Other experiments showed that ionizing radiation changed the behavior of fungal melanin – an interesting observation that warranted further investigation.

Dadachova and Casadevall’s follow-up paper in 2008 is where they first proposed a biological pathway similar to photosynthesis.

It appears that the fungus – and others like it – are harvesting ionizing radiation and converting it into energy, with melanin acting similarly to the light-absorbing pigment chlorophyll.

At the same time, melanin behaves as a protective shield against the more harmful effects of that radiation.

This appears to be supported by the findings of a 2022 paper, in which scientists describe the consequences of taking C. sphaerospermum in space and strapped to the exterior of the ISS, exposing it to the full effects of cosmic radiation.

There, sensors placed beneath the petri dishes revealed that a smaller amount of radiation penetrated through the fungus compared to the agar-only control.

The purpose of that paper was not to demonstrate or investigate radiosynthesis, but to explore the potential of fungi as radiation shields for space missions, which is a good idea. But, according to that paper, we still don’t know what the fungus is actually doing.

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Scientists have been unable to demonstrate ionizing radiation-dependent carbon fixation, metabolic benefits from ionizing radiation, or a defined energy-harvesting pathway.

“However, actual radiosynthesis has yet to be shown, let alone the reduction of carbon compounds into forms with high energy content or the fixation of inorganic carbon driven by ionizing radiation,” a team led by Stanford University engineer Nils Eversh writes.

The idea of ​​radiosynthesis is great – something like science fiction. But maybe it’s even cooler that this strange fungus is doing something we don’t understand to neutralize something so dangerous to humans.

It is not alone either. a black yeast, wangiella dermatitidisShows increased growth under ionizing radiation. Meanwhile, another fungus species, Cladosporium cladosporioidesExhibits increased melanin production but not increase under gamma or UV radiation.

So seen in practice C. sphaerospermum Not universal for melanized fungi.

Does this suggest that this is an adaptation that allows the fungus to feast on powerful light that could kill other organisms? Or is it a stress response that increases survival under reduced, but not ideal circumstances?

At this point, it’s impossible to tell.

What we do know is that this humble, velvety black fungus is doing some clever things with ionizing radiation to survive and perhaps even spread in a place that is too dangerous for humans to walk through safely; That life, indeed, finds a way.