Microscopic worms that live their lives in the highly radioactive environment of the Chernobyl Exclusion Zone (CEZ) appear to do so completely immune to radiation damage.
Nematodes collected from the area showed no signs of damage to their genome, as might be expected from organisms living in such a dangerous place. The finding, published earlier this year, does not suggest that the CEZ is safe, the researchers said. saybut rather worms are resilient and able to adapt skillfully to conditions that might be inhospitable to other species.
According to a team of biologists led by Sophia Tintori of New York University, this could offer insights into DNA repair mechanisms that could one day be adapted to human medicine.
Since the Chernobyl nuclear power plant reactor explosion in April 1986, the surrounding area and the nearby city of Pripyat in Ukraine have been strictly off-limits to anyone without government permission. Radioactive materials deposited in the environment expose organisms to extremely dangerous levels of ionizing radiation, greatly increasing the risk of mutation, cancer, and death.
It will be thousands of years before “Chernobyl,” as it is spelled in Ukraine, is habitable again. Most of us know this and stay away from it. But the animals… well, they don’t understand that they have to stay away. They go where they want, and the exclusion zone has since become a kind of radioactive animal sanctuary of 2,600 square kilometers.
Tests on animals living in the area have shown clear genetic differences with animals that do not live there. But much remains to be learned about the effects of the disaster on local ecosystems.
“Chernobyl was a tragedy of incomprehensible magnitude, but we still don’t have a clear idea of the effects of the disaster on local populations,” Tintori said at the time. “Did the sudden environmental change select species, or even individuals within a species, that were naturally more resistant to ionizing radiation?”
One way to better understand this question is to study nematodes, microscopic roundworms that live in a variety of habitats (including the bodies of other organisms). Nematodes can be remarkably resilient; there have been numerous cases of nematodes reawakening after thousands of years of freezing in permafrost.
They have a simple genome and a short life, meaning that several generations can be studied in a short time. This makes them excellent model organisms for studying a wide range of things, from biological development to DNA repair and response to toxins. That’s why Tintori and his colleagues went digging in Chernobyl to find nematodes of this species. Oschieus tipulaewhich usually lives in the soil.
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They collected hundreds of nematodes from rotting fruit, dead leaves and soil in the CEZ, using Geiger counters to measure ambient radiation and wearing protective suits against radioactive dust. The researchers cultured nearly 300 of their collected worms in the lab and selected 15 specimens from O. tipulae for genome sequencing.
These sequenced genomes were then compared to the sequenced genomes of five specimens of O. tipulae from elsewhere in the world – from the Philippines, Germany, the United States, Mauritius and Australia.
The CEZ worms were mostly more genetically similar to each other than to other worms, with genetic distance matching geographic distance for the entire sample of 20 strains. But signs of DNA damage from the radioactive environment were absent.
The team carefully analyzed the worms’ genomes and found no evidence of large-scale chromosomal rearrangements, as would be expected in a mutagenic environment. They also found no correlation between the worms’ mutation rate and the intensity of background radiation where each worm came from.
Finally, they tested the descendants of each of the 20 worm strains to determine how well the population tolerated DNA damage. While each strain had a different level of tolerance, it also had no correlation with the background radiation their ancestors were exposed to.
The team could only conclude that there is no evidence of any genetic impact of the CEZ environment on the genomes of O. tipulae.
And what they discovered could help researchers try to understand why some humans are more susceptible to cancer than others.
“Now that we know which strains of O. tipulae “Because strains are more sensitive or more tolerant to DNA damage, we can use them to study why different individuals are more likely than others to suffer the effects of carcinogens,” Tintari said.
“Thinking about how individuals respond differently to DNA-damaging agents in the environment is something that will help us gain insight into our own risk factors.”
The research was published in the Proceedings of the National Academy of Sciences.
An earlier version of this article was published in March 2024.
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