48,500

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It is the oldest “resurrected” virus to date… Scientists have managed to thaw and reproduce in the laboratory several ancient viruses, preserved for tens of thousands of years in the permafrost.

These viruses come back from afar… There are 13 of them to have been “unfrozen” from this very long storage period, thanks to 7 different samples. “Permafrost”, or permafrost, refers to ground whose temperature remains below zero for more than two years. A team of French scientists have decided to carry out laboratory tests on viruses that have been kept in this environment, in Siberia, for a very long time. To collect these samples, the researchers notably explored the intestines of a Siberian wolf, and the remains of a woolly mammoth.

The “youngest” of these viruses has been preserved for 27,000 years, while the eldest of all this little family of resurrected people has been no less than 48,500 years old. An advanced age which constitutes a record, say the scientists. Their work has so far only been published in a pre-publication journal, BioRxiv. They are therefore waiting to be reviewed by peers.

In previous work, they had managed to work on viruses “only” 30,000 years old. In their tests, all the viruses were able to infect cells. Very concretely, this means that the potential thawing of the permafrost is indeed a threat to the health of living beings, including humans.

Due to global warming, the irreversible melting of permafrost releases frozen organic matter for up to a million years, the majority of which breaks down into carbon dioxide and methane, further enhancing the greenhouse effect say the researchers. “ Part of this organic matter is also made up of resuscitated cellular microbes (prokaryotes, unicellular eukaryotes) as well as viruses that have remained dormant since prehistoric times. “.

What’s more, scientists say it might even be possible to “bring back to life” much older viruses. Indeed, the oldest permafrost would be more than a million years old: this is only an estimate, since standard carbon-14 dating methods do not work beyond 50,000 year. Who knows, therefore, what may be hiding there.

An immediate threat to the reindeer

On a more immediate time scale, some animals are already bearing the brunt of this bacteriological thaw: “ the periodic return of anthrax outbreaks devastating reindeer populations has been linked to deeper thawing of the active permafrost layer at the ground surface during unusually hot summers » : century-old spores of Bacillus anthraciswhich come from old cemeteries or animal carcasses, have thus already resurfaced.

Morphological characteristics allowing early identification of newly isolated viruses. (A) The large (1000 nm long) ovoid particle of Pandoraviruses with its characteristic ostiole at the apex (white arrowhead). (B) A mixture of Pandoravirus particles and icosahedral Megavirus particles displaying a “stargate” (white starfish-like structure crowning a vertex, white arrowhead). (C) The elongated particle of a Cedratvirus (1500 nm long) has two cap-like structures at the top (white arrowheads). (D) The elongated particle of a Pithovirus (1900 nm long) shows a single plug structure at the top (white arrowhead). (E) The large “hairy” icosahedral particle (770 nm in diameter) of a Megavirus, with its prominent “stargate” (white arrowhead). (F) The smaller (200 nm diameter) icosahedral particle typical of Asfarviruses. © Jean-Marie Alempic et al.

The viruses studied by scientists mainly belong to the “pandoravirus” family: these are “giant” viruses, which act on unicellular organisms, called “amoebas”. The researchers underline the fact that very many unknown viruses could well be dormant in the permafrost…

However, they are more or less reassuring about the possibility of controlling future epidemics: “ it is reasonable to hope that an epidemic caused by a revivified prehistoric pathogenic bacterium could be quickly controlled by the modern antibiotics at our disposal, since they target cellular structures (e.g. ribosomes) and metabolic pathways (transcription, translation or synthesis of the cell wall) conserved during the evolution of all bacterial phyla “, they explain as well. However, they also state that “bacteria carrying antibiotic resistance genes appear surprisingly widespread in permafrost”…

Source : BioRxiv

48,500-year-old ‘zombie virus’ returns from permafrost