As the world warms, vast swaths of permafrost are melting, releasing material that has been trapped in its icy grip for years. This includes a whole host of microbes that have been dormant for hundreds of millennia in some cases.
To study the emerging microbes, scientists have now revived some of these “zombie viruses” from the Siberian permafrost, including one that is nearly 50,000 years old – a record age for a frozen virus returning to a state capable of destroying other infect organisms.
The team behind the work, led by microbiologist Jean-Marie Alempic of France’s National Center for Scientific Research, says these resuscitating viruses may pose a significant threat to public health and further research needs to be done to assess the danger posed by these infectious agents can pose as they awaken from their icy slumber.
“A quarter of the northern hemisphere is covered by permanently frozen ground, known as permafrost,” the researchers write in their paper.
“As a result of global warming, the irreversible thawing of permafrost releases organic matter that has been frozen for up to a million years, most of which decomposes into carbon dioxide and methane, further amplifying the greenhouse effect.”
The 48,500-year-old amoeba virus is actually one of 13 described in a new study currently in preprint, nine of which are tens of thousands of years old. The researchers determined that they were all different from all other known viruses in terms of their genomes.
While the record-breaking virus was found under a lake, other extraction sites included mammoth wool and the guts of a Siberian wolf – all buried under permafrost. Using live single-cell amoebic cultures, the team proved that the viruses still had the potential to be contagious pathogens.
We are also seeing huge numbers of bacteria being released into the environment as the world warms, but given the antibiotics at our disposal, it could be argued that they would prove to be less of a threat. A new virus – such as SARS-CoV-2 – could be much more problematic for public health, especially as the Arctic becomes more densely populated.
“The situation would be much more disastrous in the case of plant, animal or human disease caused by the resurgence of an ancient unknown virus,” the researchers write.
“It is therefore legitimate to think about the risk of old viral particles remaining infectious and recirculating through the thawing of old permafrost layers.”
This team is in shape to diligently excavate viruses in Siberia, with a previous study detailing the discovery of a 30,000-year-old virus. Like the new record holder, it was also a pandora virus, a giant large enough to be visible with light microscopy.
The revived virus has been named Pandoravirus yedomawhich acknowledges the size and type of permafrost soil in which it was found. The researchers think that there are many more viruses to be found than just amoeba.
Many of the viruses released as the ice thaws will be completely unknown to us – although it remains to be seen how contagious these viruses will be once exposed to the light, heat and oxygen of the outside environment. These are all areas that could be explored in future studies.
Virologist Eric Delwart of the University of California, San Francisco, agrees that these giant viruses are just the beginning when it comes to exploring what lies hidden beneath the permafrost. Although Delwart was not involved in the current study, he has extensive experience in resuscitating ancient plant viruses.
“If the authors do indeed isolate living viruses from ancient permafrost, it is likely that the even smaller, simpler mammalian viruses would also survive frozen for centuries,” Delwart said. New scientist.
The study has not yet been peer reviewed, but is available on bioRxiv.