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

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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 are coming back from far away… There are 13 of them that have been “unfrozen” from this very long storage period, thanks to 7 different samples. “Permafrost”, or permafrost, refers to soil whose temperature remains below zero for more than two years. A team of French scientists has decided to conduct laboratory tests on viruses that have been stored in this environment in Siberia for a very long time. To collect these samples, the researchers explored in particular 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 oldest of this whole little family of resurrected humans has been no less than 48,500 years old. An advanced age, which constitutes a record, say the researchers. 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 viruses were able to infect cells. In concrete terms, this means that the potential thawing of the permafrost is actually a threat to the health of living beings, including humans.

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

What’s more, scientists say it may even be possible to “bring back to life” much older viruses. In fact, the oldest permafrost would be more than a million years old: this is only an estimate, as standard carbon-14 dating methods do not work beyond 50,000 years. So who knows what might 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 that devastate reindeer populations has been linked to deeper thawing of the active permafrost layer at the ground surface during unusually warm summers » : century-old traces of Bacillus anthraciswhich come from old cemeteries or animal corpses, have thus already been resurrected.

Morphological characteristics enabling early identification of newly isolated viruses. (A) The large (1000 nm long) ovoid particle of Pandoravirus with its characteristic ostiole at the tip (white arrowhead). (B) A mixture of Pandoravirus particles and icosahedral Megavirus particles showing 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 Asfarvirus. © Jean-Marie Alempic et al.

The viruses studied by scientists mainly belong to the “pandoravirus” family: these are “giant” viruses that act on single-celled organisms called “amoebae”. The researchers emphasize the fact that a great many unknown viruses may 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 revived prehistoric pathogenic bacterium can 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 also explain. But they also say that “bacteria carrying antibiotic resistance genes appear surprisingly widespread in permafrost”…

Source: BioRxiv

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