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Researchers bring 30,000-year-old giant virus to life
Giant Arctic Viruses Awakening? Climate change may hold previously unknown risks. A team of French and Russian scientists thawed viruses from the 30-meter deep permafrost in Northeast Siberia and brought them back to life. The 30,000-year-old viruses are significantly larger than all previously known giant viruses, the researchers headed by Matthieu Legendre and Julia Bartoli from the University of Aix-Marseille report in the journal "Proceedings of the National Academy of Sciences" (PNAS).
So far, according to the researchers, two very different types of giant virus were known. The viruses of the genus Megaviridae, whose prototype is the mimivirus identified ten years ago, and the viruses from the recently discovered genus Pandoraviruses. Now the researchers have identified another genus of giant viruses in the permafrost soil, which combines the properties of both previously known genera - the Pithovirus sibericum. After 30,000 years in the eternal ice, the viruses could still be revived and were immediately active again. The researchers saw this as "a safe indicator of the possible presence of pathogenic DNA viruses in permafrost soil." If the soil is thawing due to global warming or the increasing industrial use (especially oil drilling), future threats to human health from revived viruses could not are excluded, according to Legendre and Bartoli.
Viruses of exceptional size and survivability
When a core was thawed out of the Siberian permafrost, the previously unknown giant viruses woke up, which subsequently led to a fatal infection when they came into contact with a potential host - amoeba of the Acanthamoeba genus, the scientists write. The viruses were revived after 30,000 years at an average temperature of minus 18 degrees Celsius. Not only was the virus unique in its ability to survive, but also its enormous size. The viruses were visible under the light microscope in the following examinations. They reached a size of 1.5 micrometers in length, but had a surprisingly small genome compared to other giant viruses, reports Legendre and Bartoli. The size of the Pithovirus sibericum surpasses many bacteria and unicellular parasites.
Newly discovered viruses combine the property of other giant viruses
Viruses over a micron in size were considered unthinkable for a long time before the first giant viruses were discovered a good ten years ago. In the meantime, reports of newly identified types of giant viruses are piling up. They are found in a wide variety of places. For example, last summer the news of giant viruses in the sea mud off the coast of Chile went around the world. The viruses identified so far could be assigned to two different genera: the Megaviridae and the Pandora viruses. According to the researchers, the pathogens now discovered combine the properties of both genera. The amphora-like form corresponds to the Pandora viruses, but the genome is more reminiscent of the viruses of the genus Megaviridae.
Giant viruses a growing threat in the wake of climate change?
The scientists conclude that the giant virus family may be significantly larger than previously thought. So far it remains to be seen whether there are viruses among them that can be dangerous for humans. "The revival of such an ancestor of the amoeba-infecting virus can be seen as a safe indicator of the possible presence of pathogenic DNA viruses in the permafrost soil," reports the Russian-French research team. At worst, climate change would result in a massive spread of previously unknown viruses, with which future threats to human health cannot be ruled out. (fp)
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