The disaster at the Chernobyl nuclear power plant in 1986 turned the surrounding area into the most radioactive wasteland on Earth. People were evacuated, but many plants and animals continue to live in the area, despite high levels of radiation that persist nearly forty years later.

A new study has been published Proceedings of the National Academy of Sciences The study, led by researchers at New York University, found that chronic radiation from Chernobyl did not damage the genomes of the microscopic worms living there today; The scientists warned that this did not mean the area was safe, but suggested that the worms were extraordinarily resilient.

In recent years, researchers have discovered that some animals living in the Chernobyl exclusion zone, an area in northern Ukraine within a 28.6-mile radius of the power plant, are physically and genetically different from their counterparts elsewhere, raising questions about the effects of chronic disease. Radiation on DNA.

“Chernobyl was a tragedy of unimaginable magnitude, but we still do not have a complete picture of the consequences of the disaster for the local population,” said Sofia Tintori, a researcher in New York University’s Department of Biology and first author of the study. to work. “Did a sudden environmental change select for species or even individuals within a species that were naturally more resistant to ionizing radiation?”

To find out, Tintori and his colleagues turned to nematodes, tiny worms that have simple genomes and rapid reproduction, making them particularly useful in understanding fundamental biological events.

“These worms are omnivorous and fast-living, so they go through dozens of generations of evolution while typical vertebrates are still keeping up,” said Matthew Rockman, a professor of biology at NYU and senior author of the study.

“I saw footage of the restricted area and was amazed at how lush and overgrown it looked; I never thought it was full of life,” Tintori added. “If I wanted to find worms that were particularly resistant to radiation exposure, this might already be a selected landscape for it.”

chernobyl worms

In collaboration with Ukrainian scientists and American colleagues, including University of South Carolina biologist Timothy Musso, who has studied the effects of radiation from the Chernobyl and Fukushima disasters, Tintori and Rockman traveled to the Chernobyl Exclusion Zone in 2019 to test whether chronic exposure was linked to the effects of radiation from the Chernobyl Exclusion Zone. He visited. . had a noticeable impact on the worms in the area.

Equipped with Geiger counters to measure local radiation levels and personal protective equipment to guard against radioactive dust, the team collected worms from soil samples, rotting fruit and other organic materials. The worms were collected from areas with varying levels of radiation, ranging from low New York-level levels (negligible radioactivity) to high levels of space-level radiation (dangerous to humans, but whether it is dangerous to the worms is unclear).

After collecting the samples in the field, the team brought them to Musso’s field laboratory in a former apartment building in Chernobyl; Here hundreds of nematodes were isolated from soil and fruits. From there they went to a hotel in Kiev, where they isolated and cultured each worm using traveling microscopes.

In the New York University laboratory, researchers continued to study the worms; Some of this involved freezing the worms.

“We can freeze the worms and thaw them later for further research. This means we can stop evolution in the laboratory, which is not possible in most other animal models, and is invaluable when we want to compare animals with different evolutionary histories,” Rockman said.

They focused their analysis on 15 worms of a nematode species called Oscheius tipulae, which is used in genetic and evolutionary studies. They sequenced the genomes of 15 O. tipulae worms from Chernobyl and compared them to the genomes of five O. tipulae worms from other parts of the world.

DNA is different but not caused by radiation

The researchers were surprised to discover that, with the help of several different tests, they were unable to detect traces of radiation damage in the genomes of the Chernobyl worms.

“This doesn’t mean that Chernobyl is safe; rather, it means that nematodes are really hardy animals and can withstand extreme conditions,” Tintori said. “We also don’t know how long each of the worms we collected had been in the District, so we can’t be sure to what level each worm and its ancestors were exposed over the past four decades.”

Realizing that the genetic signature was missing because the worms living in Chernobyl were extremely effective at preserving or repairing their DNA, the researchers developed a system to compare how fast worm populations were growing and used this to measure the susceptibility of each worm’s offspring. The 20 genetically different worms had different types of DNA damage.

Although the worm strains differed from each other in how well they tolerated DNA damage, these differences did not correspond to the radiation levels at each collection site. Their findings suggest that Chernobyl worms were not more resistant to radiation and that the radioactive environment did not force them to evolve.

What can worms teach us about our own biology?

The findings give researchers clues about how DNA repair may differ from person to person and could lead to a better understanding of natural variation in humans, despite the genetic simplicity of O. tipulae.

“Now that we know which strains of O. tipulae are more sensitive or more tolerant to DNA damage, we can use these strains to investigate why different people are more likely than others to be affected by carcinogens,” Tintori said.

How different individuals of a species respond to DNA damage is an important question for cancer researchers trying to understand why some individuals with a genetic predisposition to cancer develop the disease while others do not.

“Considering how people respond differently to DNA-damaging agents in the environment will help us better understand our own risk factors,” Tintori said. he added.

Other authors of the study include Derin Chaglar and Patrick Ortiz from New York University, Timothy Musso from the University of South Carolina, and Ihor Chizhevsky from the State Specialized Organization “Ekocentr” in Ukraine.