By: Jingwei Zhao
46,000 years ago, a pair of tiny worms were encased in the Siberian permafrost. After digging them up, scientists were able to revive them. This significant discovery, published in the journal PLOS Genetics, shows that life could be paused indefinitely and still resumed.
The study offered insight on how these worms can survive for such long periods of time. Back in 2018, Anastasia Shatilovich, a scientist at the Institute of Physicochemical and Biological Problems in Soil Science RAS, successfully thawed two female worms from the Arctic, and revived them by simply putting them in water.
These worms, better known as nematodes, have a lifespan measured in days, and died after reproducing several generations. With the help of radiocarbon dating, the researchers determined that they were first frozen in the late Pleistocene, between 45,839 and 47,769 years ago. They were able to survive in these freezing conditions due to entering a dormant state, not to be confused with hibernation, called cryptobiosis. Scientists at the institute have yet to fully understand this process. According to Teymuras Kurzchalia, a professor emeritus at the institute, no known nematodes have achieved such a long cryptobiosis for thousands of years at a time.
Dr. Kurzchalia believes, “The major take-home message or summary of this discovery is that it is, in principle, possible to stop life for more or less an indefinite time and then restart it.” Researchers were able to identify the genes that made these nematodes enter cryptobiosis; these genes are also found in the contemporary nematode called Caenorhabditis elegans, which can also reach the dormant state. According to Dr. Kurzchalia, “This led us, for instance, to understand that they cannot survive without a specific sugar called trehalose. Without this sugar, they just die.”
The mysterious Siberian permafrost has offered researchers the chance to uncover deadly ancient viruses, mummified bodies, as well as many microscopic creatures. During the pandemic, many have expressed fear of the consequences of resurrecting ancient microorganisms, but Dr. Kurzchalia has a different view: these organisms are studied in fully controlled environments, so these people have nothing to worry about. He believes that there are more important matters to attend to, such as how global warming has been significantly melting more of the Siberian permafrost, and he further believes that there will be no control over what is unearthed. Luckily, these ancient worms are perfectly safe, and although they died in during the study, this was expected considering their short lifespan.
He thinks that although there are no practical applications of cryptobiosis, these researchers should still learn more about the state. This case is like the discoveries of semiconductors and the double helix structure of DNA, which had decades with no practical uses, but were eventually revolutionary. Dr. Kurzchalia also added that cryptobiosis could perhaps one day be engineered by humans.