An international team of scientists has managed to bring a nematode back to life after spending some 46,000 years, since the Pleistocene, frozen beneath the Siberian permafrost. The worm, which was found 40 meters below the surface, is a species new to science. Some animals, such as the ultra-resistant tardigrades (which live without water for decades and withstand radiation), rotifers (multicellular beings that are only visible under a microscope), and nematodes, can survive adverse conditions by entering a state of dormancy known as cryptobiosis. This is not the first time researchers have brought these creatures back after thousands of years of freezing. In 2018, for example, the thawing of the Siberian permafrost allowed the resurrection of 42,000-year-old nematodes. In the new study, published Thursday in PLoS Genetics, Anastasia Shatilovich of the Institute of Physicochemical and Biological Problems in Soil Science (RAS) in Russia managed to revive two nematodes frozen in a fossilized burrow in silt deposits in the permafrost. After thawing the worms in the laboratory, radiocarbon analysis of plant material from the burrow revealed that these intact deposits, at a depth of 40 meters, had not thawed since the late Pleistocene, between 45,839 and 47,769 years ago. Related News standard No Scientists 'resurrect' a 'zombie' virus that spent 48,500 years frozen in permafrost David Sánchez de Castro Discovered in the ice of Siberia, it is the oldest virus known to date Researchers began working with the worms to try to understand what molecular and metabolic pathways these organisms use to remain dormant and for how long they can suspend life as 'zombies', something that is not fully understood. Through genome sequencing, assembly, and phylogenetic analysis of the nematode's relationship to modern species, the researchers determined that the worms belong to a previously undescribed species, which they named Panagrolaimus kolymaensis , in recognition of the Kolyma River region where it originated. By comparing its genome to that of the model organism, Caenorhabditis elegans , they identified common genes that are involved in cryptobiosis. The Risk of 'Time-Traveling' Pathogens Ancient pathogens escaping from melting permafrost have a real potential to harm microbial communities and could potentially threaten human health, according to a new study by Giovanni Strona and his team at the European Commission's Joint Research Centre, published in PLOS Computational Biology. Strona quantified the ecological risks posed by these microbes using computer simulations. He ran a simulation in which virus-like digital pathogens invade communities of bacteria-like hosts. The ancient pathogens were often able to survive and evolve. 3% became dominant. And around 1%, they produced unpredictable results: some caused the extinction of up to a third of the host species. The researchers say that while this percentage may seem small, it can still pose a considerable danger. The risks posed by revived pathogens, until now limited to science fiction stories, could be powerful drivers of ecological change and threats to human health. Freezing record When mildly desiccated in the lab, both species increased production of a sugar called trehalose, which can help them survive severe desiccation and freezing. They tested the survival capabilities of P. kolymaensis and found that exposure to mild desiccation before freezing helped prime the worms for cryptobiosis and improved survival at an extreme temperature of -80°C. This treatment also benefited C. elegans larvae, which then survived 480 days at -80°C with no reductions in viability or reproduction after thawing. This study extends the longest cryptobiosis discovered in nematodes by thousands of years. By adapting to cope with extreme conditions, such as permafrost, for short periods of time, nematodes may have gained the potential to remain dormant over geological timescales. MORE INFORMATION news No The two oldest known families discovered: up to seven generations without a trace of infidelity news No The ocean currents that regulate global temperature could stop by 2025 with serious consequences for the climate "Our findings are essential for understanding evolutionary processes because generation times can vary from days to millennia and because the long-term survival of individuals of a species can result in the resurgence of lineages that would otherwise have become extinct," concludes Philipp Schiffer, one of the authors who supervised the study. The researcher is convinced that "studying the adaptation of species to such extreme environments by analyzing their genomes will allow us to develop better conservation strategies in the face of global warming."
