Life can tame even deadly radiation and use its energy for the benefit of new creatures.
Contrary to many expectations, the disaster at the Chernobyl nuclear power plant did not turn the surrounding forests into a dead nuclear desert. There is no silver lining, and after the establishment of the exclusion zone, anthropogenic pressure on the local nature sharply decreased. Even in the most damaged areas, plant life quickly recovered; wild boars, bears and wolves returned to the Pripyat valley. Nature comes to life like a fabulous Phoenix, but an invisible suffocating grip of radiation is felt everywhere.
“We walked through the forest, the sky turned into a magnificent sunset,” says Christopher Robinson, an American microbiologist who worked there in 2018. – In a wide meadow, we met horses, about forty. And everyone had yellow eyes, with difficulty distinguishing us, passing by. ”
In fact, animals massively suffer from cataracts: vision is especially sensitive to radiation, and blindness is the usual result of a long life in the exclusion zone. In local animals, developmental disorders are often found, cancer often occurs. And even more so, it is fatal to stay near the former epicenter of the accident.
The fourth block, which exploded in 1986, a few months later was sheltered by a protective sarcophagus, which collected other radioactive waste from the site. But already in 1991, when microbiologist Nelly Zhdanova and her colleagues examined these residues with the help of remotely controlled manipulators, life was revealed here. The deadly debris has been populated by thriving communities of black mushrooms. Over the following years, representatives of approximately one hundred species were identified among them. Some of them not only withstand the murderous level of radiation, but are even drawn to it, like plants – to the light.
High-energy radiation is dangerous for all living things. It easily damages DNA, causing mutations and errors in the code. Heavy particles can break down chemical compounds like cannonballs, leading to the appearance of active radicals that immediately interact with the first neighbor they come across. A sufficiently intense bombardment can cause the radiolysis of water molecules and a shower of random reactions that kill the cell. Despite this, some creatures demonstrate amazing resistance to such an impact.
Unicellular organisms are relatively simple in structure, and it is not so easy to disrupt their metabolism by free radicals, and powerful protein repair tools quickly repair damaged DNA. As a result, fungi can absorb up to 17,000 Grays of radiation energy – many orders of magnitude more safe for humans. Moreover, some of them literally enjoy such a radioactive “rain”.
The famous Evolution Canyon near Mount Carmel in Israel with one slope oriented towards Europe, the other towards Africa. The difference between their illumination reaches 800%, and the “African” slope exposed to the sun is inhabited by fungi that grow better in the presence of radiation. Like those found in Chernobyl, they look black due to the large amounts of melanin. This pigment is able to intercept high-energy particles and dissipate their energy, keeping cells from damage.
Having dissolved such a mushroom cell, under the microscope you can see its “ghost” – the black silhouette of melanin, which accumulates in the cell wall in concentric layers. Mushrooms on the “African” side of the canyon contain three times as much as the inhabitants of the “European” slope. They are rich in many microbes living on the highlands, which in vivo receive up to 500-1000 Gray per year. But even such a decent amount of absorbed radiation for mushrooms is nothing. It is unlikely that all this melanin is produced for protection alone.
Nelly Zhdanova in 1991 demonstrated that the mushrooms taken near the Chernobyl reactor stretch in the direction of the radiation source and grow better in her presence. In 2007, these results were developed by US biologists Arturo Casadevalu and Ekaterina Dadachova. Scientists have shown that under the influence of radiation hundreds of times higher than the natural background, black melanized mushrooms (Cladosporium sphaerospermum, Wangiella dermatitidis and Cryptococcus neoformans) absorb carbon from the nutrient medium three times more intensively. At the same time, mutant albino mushrooms, incapable of producing melanin, transferred the radiation easily, but grew at the usual pace.
It is worth saying that melanin can be present in cells in slightly different chemical configurations. Its main form in humans is eumelanin, it protects the skin from ultraviolet radiation and gives it a brown-black color. The red color of the lips and nipples is determined by the presence of pheomelanin. And it is pheomelanin that produces fungal cells under the influence of radiation, although in such quantities it looks completely black.
The transition from eu to pheomelanin is accompanied by increased electron transfer from NADP to ferricyanide – this is one of the first steps in glucose biosynthesis. It is not surprising that, according to some assumptions, such fungi are capable of carrying out reactions similar to photosynthesis, but instead of light they use the energy of radioactive radiation. This ability allows them to survive and thrive where more complex and fastidious organisms die.
Large amounts of highly melanized fungal spores are found in sediments of the early Cretaceous period. In that era, many animals and plants died out: “This period coincides with the transition through the“ magnetic zero ”and the temporary loss of the“ geomagnetic shield ”that protects the Earth from radiation,” writes Ekaterina Dadachova. Such a situation could not take advantage of the mushrooms, radiotrophs. Sooner or later, we will take advantage of this.
The use of melanin to utilize radiation energy is just a hypothesis. However, research continues, the benefit of the radiotrophs can not be called something exotic. In conditions of a lack of resources and sufficient radiation, some common mushrooms can enhance the synthesis of melanin and show the ability to “eat radiation.” For example, the above C. sphaerospermum and W. dermatitidis are widespread soil organisms, while C. neoformans sometimes infect humans, causing infectious cryptococcosis.