Scientists found the oldest viruses in the Siberian permafrost… and some of them are still contagious
(Jean-Marie Alempic et al. / bioRxiv, 2022 https://bit.ly/3OF0euy)
A team of international researchers have found 13 viruses up to 48.5 thousand years old in samples of Siberian permafrost, making them the oldest known at the moment.
A genome sequencing indicated that they belonged to five clades, four of which were not previously found in permafrost.
Also, some paleopathogens retained the ability to replicate and infect eukaryotic organisms: they are still contagious.
According to the forecasts of the Intergovernmental Panel on Climate Change (IPCC), the average temperature on Earth will increase by 1.5°C compared to the second half of the 19th century.
This effect is most pronounced in the Arctic, where warming is occurring twice as fast as in temperate climates.
The most obvious consequence of this is the melting of permafrost at ever-increasing depths and its erosion.
Because of this, bacteria, archaea and viruses that have been frozen for up to a million years (the estimated age of permafrost) can be released.
Of them, the viruses represent the greatest potential danger, since they are not sensitive to antibiotics.
The reality of the threat was confirmed by Jean-Michel Claverie and colleagues in 2014–2015.
They described DNA-containing viruses of the genera Pithovirus and Mollivirus pathogenic for amoebas, 30 thousand years old, found in the Siberian permafrost.
THE NEW VIRUSES
After that, a team of scientists from Russia and France analyzed 7 samples from different regions of the Siberian permafrost.
The samples came from:
- under the bottom of the lake
- from a melting ice fault
- from biosamples of frozen mammoths and wolves
- from the Lena River (Yakutsk, Russia) and Shchapina River (Kamchatka)
Their supernatants were introduced into cultures of the amoeba Acanthamoeba castellanii in Petri dishes.
Then, after 72 hours, morphological changes characteristic of a viral infection were observed in some cells:
- rounding
- lack of adhesion
- encystation
- nuclear deformation
- lysis
- cytoplasmic regions of virion assembly
They were used to characterize viruses using transmission electron microscopy, polymerase chain reaction, purification, cloning, viral DNA extraction and sequencing.
The researchers were able to identify 13 giant DNA-containing viruses.
Seven of them were assigned to the genus Pandoravirus of the Pandoraviridae family (one of the largest viruses with the longest known DNA - up to 2.6 megabytes):
- P. lena (from Lena River),
- P. talik (from under the bottom of the lake Yukechi Alas)
- P. yedoma (from under the bottom of the lake Yukechi Alas)
- P. duvanny (from melting ice in Duvanny Yar),
- 2 strains of P. mammoth (from the stomach of a frozen mammoth and soil with mammoth wool)
- P. lupus (from the intestines of a frozen wolf).
Three viruses belong to the genus Cedratvirus of the Pithoviridae family:
- C. kamchatka (from Kamchatka cryosol),
- C. lena (from Lena),
- C. duvanny (from Duvanny Yar).
Pithovirus mammoth of the same family and Megavirus mammoth of the Mimiviridae family were found in frozen soil with mammoth wool,
At the same time, the Pacmanvirus lupus of the Asfarviridae family were found in the intestines of the wolf.
Most of the listed clades are not yet registered in the database of the International Committee on the Taxonomy of Viruses (ICTV).
Pandoraviruses, cedratviruses, megaviruses and pacmanviruses have not been found in permafrost before.
The age of the finds ranged from 27 thousand years (intestinal contents of a wolf and soil with mammoth wool) to 48.5 thousand years (P. yedoma).
The P. tedoma is the oldest known virus.
Sources:
- bioRxiv: https://www.biorxiv.org/content/10.1101/2022.11.10.515937v1.full
- ScienceAlert: https://www.sciencealert.com/scientists-revived-ancient-zombie-viruses-frozen-for-eons-in-siberia
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