Explained: Scientists 'Revive' 46,000-Year-Old Worms Frozen In Ice, How And Why Did They Do It?

Scientists have revived worms frozen in the polar ice for 46,000 years. The worms have been found to have been from a previously unknown species. 

The discovery, published in a paper in journal PLOS Genetics last month, helps understand the process by which organisms can 'pause' life for thousands of years. 

The study comes at a time when scientists are increasingly getting concerned that the melting of ice from global warming could release pathogens, such as viruses and bacterias, frozen in ice for thousands of years into the environment. Such pathogens could then potentially infect animals and humans. 

The study regarding the two worms, however, is more concerned about understanding how organisms can 'pause' their metabolic process to stay frozen in time through eras. These worms have been frozen for 46,000 years. For context, humans started practicing agriculture around 10,000 years ago and first cities appeared around 8,000 years ago. The worms thus predate the first signs of settled human life. 

Here we explain what the scientists found by reviving these worms and what implications this kind of research has. 

How did scientists revive 46,000-year-old worms?

These two frozen worms were extracted from Siberian permafrost by Russian scientists in 2018. 

These worms, called nematodes in scientific language, survived for around 46,000 years by 'pausing' their metabolic functions in the polar ice. 

The worms were revived simply by putting them in water at the Max Planck Institute of Molecular Cell Biology and Genetics in Germany, reported The New York Times.

However, once revived, the worms died within days, as per their life cycle, but reproduced several generations, said the report. 

The carbon-dating of the worms revealed they were frozen between 45,839 and 47,769 years ago.

They survived for all these years through a process called cryptobiosis.

The NYT reported, "The roughly millimeter-long worms were able to resist extreme low temperatures by entering a dormant state called cryptobiosis, a process researchers at the institute have been trying to understand. No nematodes had been known to achieve such a dormant state for thousands of years at a time, Teymuras Kurzchalia, a professor emeritus at the institute who was involved in the study, said on Saturday."

What is cryptobiosis?

In simple terms, cryptobiosis is a condition in which an organisms goes into a state of extreme inactivity —pauses its body functions— in adverse conditions.

The idea is that once environmental conditions are ideal again, the organism would come back to life. 

These worms, too, were revived when put into water after being frozen for around 46,000 years.

A post by University of Hawaii at Manoa states: "All living organisms use enzymes to complete metabolism, converting chemical compounds into the usable energy needed to survive. However, some organisms are capable of suspending their metabolism.
 
"Cryptobiosis is a state of extreme inactivity in response to adverse environmental conditions. In the cryptobiotic state, all metabolic procedures stop, preventing reproduction, development, and repair. In cryptobiosis, an organism can live almost indefinitely while it waits for environmental conditions to become better."

The scientists in their study, published as a paper titled "A novel nematode species from the Siberian permafrost shares adaptive mechanisms for cryptobiotic survival with C. elegans dauer larva" in PLOS Genetic journal, listed some other organisms that can go into cryptobiosis"

Bacillus spore preserved in the abdomen of bees buried in amber for 25 to 40 million years and a 1000 to 1500 years-old Lotus seed in an ancient lake
Metazoans such as tardigrades, rotifers, and nematodes 

What did the study find?

The major highlight of the study is that it found that it is possible to stop or pause life for a very long period of time. 

Researchers identified key genes in the nematode that allow it to achieve the cryptobiotic state, reported NYT. It is a special type of sugar called trehalose.

"This led us, for instance, to understand that they cannot survive without a specific sugar called trehalose. Without this sugar, they just die," said Teymuras Kurzchalia, Professor Emeritus, Max Planck Institute of Molecular Cell Biology and Genetics in Germany, to NYT.

Cryptobiosis could, perhaps one day, be engineered by humans, added Kurzchalia.

Another researcher in the study, Dr. Philipp Schiffer of the Institute for Zoology at the University of Cologne, told NYT that the more relevant application of the findings "is that in times of global warming we can learn a lot about adaptation to extreme environmental conditions from these organisms, informing conservation strategies and protecting ecosystems from collapsing".

The scientists also said that the study could help understand how to save ties and cells for a long time, noting in their paper: "Finally, understanding the precise mechanisms of long-term cryptobiosis and cues that lead to successful revivals can inform new methods for long term storage of cells and tissues."

Notably, the study comes at a time when there are concerns among scientists that melting ice could also unleash pathogens frozen for millions of years. These pathogens, such as viruses or bacterias, can predate modern humans and will be completely new to us, thus having no pre-set treatment when they first infect humans or animals. Moreover, diseases completely unknown to humans —that may predate humans entirely— could also potentially make a comeback. 

"More than 100 diverse microorganisms in Siberia’s deep permafrost have been found to be antibiotic resistant. As the permafrost thaws, there is potential for these bacteria to mix with meltwater and create new antibiotic-resistant strains," notes a paper titled 'Emergent biogeochemical risks from Arctic permafrost degradation' in Nature Climate Change Journal.

The scientists of the 'worm study' also acknowledged the concerns over pathogens —though briefly— in the paper.

"These findings have implications for our understanding of evolutionary processes, as generation times may be stretched from days to millennia, and long-term survival of individuals of species can lead to the refoundation of otherwise extinct lineages. This is particularly interesting in the case of parthenogenetic species, as each individual can find a new population without the need for mate finding, i.e. evading the cost of sex," noted the scientists in their paper.