Chernobyl is teeming with worms resistant to radiation

The 1986 Chernobyl nuclear disaster indelibly marked the region as the most radioactive environment on the planet, leading to the mass evacuation of humans. Despite the high radiation levels that persist nearly four decades later, a diverse array of flora and fauna continues to inhabit the area. 

A study led by researchers at NYU has shed light on the remarkable genetic resilience of microscopic worms in the Chernobyl zone. While it does not indicate that the area is safe, this finding underscores the extraordinary adaptability of these organisms to extreme conditions.

Chernobyl radiation and wildlife

The Chernobyl Exclusion Zone, encompassing an area within an 18.6-mile radius of the power plant in northern Ukraine, has become a living laboratory for scientists studying the impacts of prolonged radiation exposure on wildlife. 

Observations have revealed that animals within the zone exhibit distinct physical and genetic characteristics compared to those living in less contaminated environments. This has propelled scientific inquiry into how chronic radiation exposure influences DNA.

“Chernobyl was a tragedy of incomprehensible scale, but we still don’t have a great grasp on the effects of the disaster on local populations. Did the sudden environmental shift select for species, or even individuals within a species, that are naturally more resistant to ionizing radiation?” said lead author Sophia Tintori, a postdoctoral associate in the Department of Biology at NYU.

Tiny worms that live fast

The research team, seeking answers, focused their efforts on nematodes – tiny worms noted for their simplistic genomes and rapid life cycles, which render them particularly valuable for fundamental biological research. 

“These worms live everywhere, and they live quickly, so they go through dozens of generations of evolution while a typical vertebrate is still putting on its shoes,” explained senior author Matthew Rockman, a professor of biology at NYU.

“I had seen footage of the exclusion zone and was surprised by how lush and overgrown it looked – I’d never thought of it as teeming with life,” Tintori added. “If I want to find worms that are particularly tolerant to radiation exposure, this is a landscape that might have already been selected for that.”

Enhanced tolerance to radiation

This prompted Tintori to consider the possibility that the area might have naturally selected for organisms with an enhanced tolerance to radiation. 

To explore this hypothesis, the research team, including collaborators from Ukraine and the United States such as biologist Timothy Mousseau of the University of South Carolina, embarked on a field expedition to the Chernobyl Exclusion Zone in 2019. 

How the research was conducted 

Equipped with Geiger counters and protective gear, they meticulously collected worm samples from various locations, encountering radiation levels ranging from minimal to extremely high.

Upon collecting the samples, the researchers transported them to Mousseau’s field lab in Chernobyl for initial analysis. They then continued their examinations in a hotel in Kyiv, isolating and cultivating nematodes using travel microscopes. 

Back at NYU, the team leveraged cryopreservation techniques to halt the worms’ evolution, allowing for a comparative analysis of specimens that had experienced different evolutionary histories.

Genetic resilience of Chernobyl worms

The investigation centered on 15 worms of the species Oscheius tipulae, known for its relevance in genetic and evolutionary research. 

By sequencing the genomes of these Chernobyl worms and comparing them to those of O. tipulae from other regions, the researchers anticipated uncovering radiation-induced genetic alterations. However, their findings did not support this hypothesis.

“This doesn’t mean that Chornobyl is safe – it more likely means that nematodes are really resilient animals and can withstand extreme conditions,” said Tintori. “We also don’t know how long each of the worms we collected was in the Zone, so we can’t be sure exactly what level of exposure each worm and its ancestors received over the past four decades.”

Chernobyl worms were not phased by radiation

Intrigued by the absence of a genetic signature from radiation, the team devised an experiment to assess the worms’ growth rates and sensitivity to various types of DNA damage. 

Despite observing differences in DNA damage tolerance among the worm lineages, these variations did not align with the radiation levels at their collection sites, suggesting that the Chernobyl nematodes had not evolved a specific resistance to radiation.

DNA repair mechanisms 

This groundbreaking research not only highlights the nematodes’ resilience but also paves the way for future studies into DNA repair mechanisms across different organisms, including humans. 

“Now that we know which strains of O. tipulae are more sensitive or more tolerant to DNA damage, we can use these strains to study why different individuals are more likely than others to suffer the effects of carcinogens,” Tintori explained. 

Broader implications 

As Tintori points out, contemplating individual variability in response to environmental DNA-damaging agents enriches our understanding of personal cancer risk factors. 

The study – published in the journal Proceedings of the National Academy of Sciences – not only contributes to the field of evolutionary biology and genetics but also offers insights into human health, emphasizing the significance of genetic research in identifying and mitigating vulnerabilities to environmental carcinogens.

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