Tiny worms living in the highly radioactive environment of the Chernobyl Exclusion Zone (CEZ) appear to have no radiation damage at all.
Nematodes collected from this area showed no signs of damage to their genomes, contrary to what would be expected of an organism living in such a dangerous place. The researchers say this finding does not indicate that CEZ is safe, but rather that the worms are resilient and proficient in adapting to conditions that may not be suitable for other species.
A team of biologists led by Sophia Tintori of New York University said this could shed some insight into DNA repair mechanisms that could one day be used in human medicine.
Since the Chernobyl NPP reactor in April 1986**, the area around the Chernobyl NPP and the nearby Ukrainian town of Pripyat have been strictly off-limits to anyone without approval. Radioactive material deposited into the environment exposes organisms to extremely unsafe levels of ionizing radiation, greatly increasing the risk of mutations, cancer, and death.
Thousands of years later, the Ukrainian spelling "Chernobyl" will be safe for human habitation again. Most of us know this and steer clear of it accordingly. But animals....Well, they don't understand to stay away. They went as much as they wanted, and the exclusion zone has since become a strange radioactive animal sanctuary covering 2,600 square kilometers (1,000 square miles).
Tests on animals living in the area have shown that they have significant genetic differences from animals that do not live in the area. But there is still a lot we don't know about the impact of this disaster on local ecosystems.
"Chernobyl is a tragedy of incomprehensible scale, but we still don't have a good understanding of the impact of this disaster on the local population," Tintori said. ”。Did the abrupt change in the environment select species that are naturally more resistant to ionizing radiation, or even individuals within a species? ”
One way to get to the bottom of this problem is to look at nematodes – tiny roundworms that live in a range of habitats, including the bodies of other organisms. Nematodes can be very tenacious; After thousands of years of freezing in permafrost, there have been many cases of nematodes reawakening.
Their simple genomes and short lifespans mean that multiple generations can be studied in a short period of time. This makes them excellent model organisms for studying a range of things, from biological development to DNA repair and toxin responses. That's why Tintori and her colleagues dig in Choronbyl to look for the Iopla Oschieus nematodes, which usually live in the soil.
They collected hundreds of nematodes from the soil of decaying fruits, fallen leaves, and CEZs, measured ambient radiation with Geiger counters, and wore protective suits against radioactive fallout. The researchers cultured nearly 300 collected worms in the laboratory and selected 15 Tipra's OTipulae specimens were subjected to genome sequencing.
These sequenced genomes were then compared with five Tiprai O. from other parts of the world – the Philippines, Germany, the United States, Mauritius and AustraliaComparison of sequenced genomes of tipulae specimens.
CEZ worms are mostly genetically similar to other worms, and the genetic distance corresponds to the geographic distance of the entire 20 strain samples. But there is a lack of signs of DNA damage from a radiant environment.
The team carefully analyzed the worm's genome and found no evidence that the mutated environment caused massive chromosomal rearrangements. They also found that there was no correlation between the mutation rate of the worms and the intensity of ambient radiation at the location of each worm.
Finally, they tested the offspring of 20 worm strains to determine how well the population tolerated DNA damage. Although each lineage has a different level of tolerance, this is also independent of the environmental radiation to which their ancestors were exposed.
The team could only conclude that there was no evidence that the CEZ environment had any genetic effect on the Tippella genome.
Their findings could help researchers figure out why some people are more likely to develop cancer than others.
"Now that we know which strains are more susceptible or more tolerant to DNA damage, we can use these strains to study why different individuals are more susceptible to carcinogens than others," Tintari said. ”。
Thinking about how individuals respond differently to DNA damaging factors in the environment will help us get a clear picture of our own risk factors. ”