Tiny worms that dwell in the Chernobyl Exclusion Zone (CEZ), which is highly radioactive, have been observed to be radiation-proof and free from damage in a new study.
Highly Radioactive CEZ
Dr. Sophia Tintori, the study's lead author, explains that Chernobyl was a disaster with a grave and incomprehensible scale. It took place in 1986 and transformed the area into Earth's most radioactive landscape. However, not much is known about the tragedy's effects on local populations.
While humans were evacuated from the area, several animals and plants still dwell in the area, despite the high radioactivity that continues after almost 40 years.
In the past years, scientists were able to find some animals that still live in the CEZ, which has an 18.6-mile radius, and that are genetically and physically different from their counterparts in different areas. This has raised questions regarding how long-term radiation exposure could affect DNA.
Radiation-Proof Worms
As part of the study, the researchers went to Chernobyl to examine Oschieus tipulae nematodes, which are small worms that have rapid reproduction and simple genomes. Such features make them quite useful for knowing more about basic biological phenomena.
Matthew Rockman, the study's senior author and a biology professor from NYU, explains that these worms live anywhere and do so quickly. Hence, they experience dozens of generations of evolution.
The researchers gathered nematodes from rotting fruit, soil, and organic material samples. The worms were taken from areas across the zone with varying radiation exposure amounts. The researchers then proceeded to study the worms back at the NYU lab.
The scientists cultured almost 300 specimens of the worms they gathered. They also chose 15 O. tipulae specimens for further genomic sequencing. The genomes that were sequenced were then compared to other O. tipulae specimens from other parts of the world.
The nematodes were found to exhibit no sign of genomic damage. This contrasts with what is expected from organisms that dwell in such dangerous areas.
The worms from the CEZ were observed to be more genetically similar to each other compared to other worms. Their genetic distance matched the geographic distance for a full 20-strain sample. Interestingly, no DNA damage due to radiation was observed.
Upon carefully analyzing the genome of the worms, they did not find any evidence of wide chromosomal rearrangements that were expected to result from the environment the worms were exposed to. They also observed no correlation between the worms' mutation rate and the ambient radiation strength at the locations the worms were taken from.
They also performed tests on the descendants of each of the 20 strains of worms to see how the population could tolerate damage to DNA. While each strain was found to have varying tolerance levels, the researchers found no correlation with the ambient radiation that their ancestors were previously exposed to.
The researchers note that such findings don't imply that the CEZ is a safe area. Rather, it means that the worms have become resilient and have been able to adapt to conditions that other species would have found to be inhospitable. Such findings were noted in the "Environmental radiation exposure at Chornobyl has not systematically affected the genomes or chemical mutagen tolerance phenotypes of local worms" study.
The scientists concluded that there is no proof that the CEZ environment genetically impacted O. tipulae's genomes.
Such findings offer clues regarding how DNA repair can be different across individuals. Moreover, despite nematodes' genetic simplicity, the results could shed more light on the natural variations among humans.
This could offer insight on the repair mechanisms of DNA that could possibly be adapted for human medical applications.
Dr. Tintori explains that since they now know which O. tipulae strains are more tolerant and sensitive to DNA damage, they can make use of such strains to learn more about why some individuals are more likely to suffer from carcinogenic effects.
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