Permafrost melts in the Kolyma River outside Zyryanka, Russia, Siberia on July 4, 2019
The permafrost of Siberia holds secrets that are thousands or even millions of years old, some of which could pose a threat to humanity. According to the March 2023 issue of Viruses, scientists isolated 13 ancient viruses from thawed permafrost samples, four of which were new viruses that had never been seen before. These viruses are called "zombie" viruses because they become active again after a long period of dormancy under extreme conditions.
These viruses belong to a special type called giant viruses, which are much larger than ordinary viruses and have more complex genomes. Giant viruses primarily infect single-celled organisms such as microalgae and protozoa, and are able to form huge "factories" within host cells to replicate themselves.
This is a giant virus isolated in 2014 from 30,000-year-old permafrost samples
The giant virus was only discovered in 2003 and remains one of the mysteries of the microbiology community. Scientists don't know how they evolved such large and complex structures and functions, and what their relationship to other life forms is. By analyzing ancient giant viruses preserved in permafrost, scientists hope to uncover their origins and evolutionary history.
However, these "zombie" giant viruses have also raised concerns about their potential dangers. As global warming accelerates the melting of permafrost, will more unknown or extinct microbes be released and potentially infect humans or animals? So far, there is no evidence that any giant virus can directly infect humans or other multicellular organisms. However, scientists cannot rule out this possibility.
(A) Large ovate granules (length 2 nm) of Pandora virus yedoma (strain Y1000)
On the one hand, giant viruses may indirectly affect human health or environmental balance by affecting their host cells. For example, in 2019 there was an outbreak of pulmonary flukes caused by parasites, infecting more than 10 million people and killing at least 40 people in some countries. It was later discovered that there was a giant virus called Mavirus (Maverick virus) in the parasite, which suppressed the replication of another giant virus infected by the parasite, CroV (Cafeteria roenbergensis virus). Therefore, Mavirus may play an important role in regulating microbial communities in marine ecosystems.
It is a giant virus isolated in 2013 from sediments off the coast of Chile
Giant viruses, on the other hand, may expand their host range through mutation or recombination, potentially infecting humans or other multicellular organisms. In fact, there is already some evidence of an interaction between giant viruses and the human immune system. For example, in 2017, scientists discovered a giant virus called Klosneuvirus (Klosneu virus), which is able to recognize and use receptors on human immune cells to enter cells . Although this virus has not been found in humans, it shows that giant viruses have the potential to adapt to different hosts .
Therefore, scientists call for strengthening the monitoring and evaluation of microorganisms in permafrost, and establishing corresponding precautions and contingency plans to prevent any potential epidemic or ecological disaster. At the same time, they also hope to use these "zombie" giant viruses to provide new clues and perspectives for peeping into the history of the earth and the origin of life.
bibliography
- ‘Zombie’ viruses have been revived from Siberian permafrost. Could they infect people? By Joanna Thompson published 6 December 2022 https://www.livescience.com/zombie-viruses-permafrost-siberia
- Viruses in permafrost: Scientists have revived a ‘zombie’ virus that infected animals before humans existed. By Katie Hunt published 8 March 2023 https://www.cnn.com/2023/03/08/world/permafrost-virus-risk-climate-scn/index.html
- Scientists discover ancient ‘zombie’ viruses in Siberian permafrost samples. By Aaron Reich published 10 March 2023 https://www.jpost.com/environment-and-climate-change/article-733926
- Nature: Viral phage mavirus allows single-celled organisms to develop adaptive immunity to giant viruses. By Bioon News published 9 February 2011 https://news.bioon.com/article/6695411.html
- Mavirus - Wikipedia https://en.wikipedia.org/wiki/Mavirus