A group of scientists led by Professor Jean-Michel Claverie and Dr. Chantal Abergel of the French University of Aix-Marseille (Aix-Marseille Université) has discovered a previously unknown virus. Called Pithovirus sibericum, it’s very special because it’s gigantic by the standards of the viruses and was revived after being hibernated in the Siberian permafrost for more than 30,000 years.
In an article published in the journal “Proceedings of the National Academy of Sciences”, Jean-Michel Claverie and Chantal Abergel describe their discovery. The two are specialists in the field of giant viruses and over the years have discovered the Megavirus (photo ©Chantal Abergel) in 2010 and the Pandoraviruses in 2013. The latter were the biggest viruses ever found but the Pithovirus sibericum is even bigger. In fact, the Pandoravirus have a length of about 1 micron, that is a thousandth of a millimeter, and a half microns in diameter but the Pithovirus sibericum is even longer with its 1.5 micron.
However, size isn’t everything. It’s estimated that Pithovirus sibericum contains about 500 genes while the Pandoravirus salinus has 2,500 genes. It’s always a huge amount when you consider that the influenza virus contains only 13 genes. The DNA of this new giant virus is packed in a much less densely than regular viruses, helping to determine its size.
The Pithovirus sibericum was found in Russia, precisely at a depth of about 30 meters in the permafrost of north-eastern Siberia. A group of Russian scientists took a sample and sent it to France, to the laboratory of Jean -Michel Claverie and Chantal Abergel.
In the laboratory, the ice was melted and placed in a cell culture of amoebas suitably treated to prevent contamination by bacteria or fungi. The day after the amoebae were dead. The Pithovirus sibericum was the only possible culprit. Subsequent tests have shown that these giant viruses don’t infect animal cells.
The demonstration that a very old virus can remain frozen and come back on when the ice melts opens up perspectives that may be of concern. In the past, concerns for that kind of possibility have already been expressed but the present climate change is increasing them. The Pithovirus sibericum is harmless but the next ancient virus that will wake up might be dangerous for human beings. That’s one more reason to study in depth the cases that are discovered, whether they’re giant or normal-size viruses.
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