A new type of giant virus called "Pithovirus" has been discovered in the frozen ground of extreme north-eastern Siberia by researchers from the Information Génomique et Structurale laboratory (CNRS/AMU), in association with teams from the Biologie à Grande Echelle laboratory (CEA/INSERM/Université Joseph Fourier), Génoscope (CEA/CNRS), and the Russian Academy of Sciences. Buried underground, this giant virus, which is harmless to humans and animals, has survived being frozen for more than 30,000 years. Although its size and amphora shape are reminiscent of Pandoravirus, analysis of its genome and replication mechanism proves that Pithovirus is very different. This work brings to three the number of distinct families of giant viruses. The discovery was reported online on March 3, 2014 in PNAS. In the families Megaviridae (represented in particular by Mimivirus, discovered in 2003) and Pandoraviridae, researchers thought they had classified the diversity of giant viruses (the only viruses visible under optical microscopy, because their diameter exceeds 0.5 microns). These viruses, which infect amoeba such as Acanthamoeba, contain a very large number of genes compared to common viruses (like influenza or AIDS, which only contain about ten genes). Their genome is about the same size or even larger than that of many bacteria. By studying a sample from the frozen ground of extreme north-eastern Siberia, in the Chukotka autonomous region, researchers were surprised to discover a new giant virus more than 30,000 years old (contemporaneous with the extinction of Neanderthal man), which they have named "Pithovirus sibericum." Because of its amphora shape, similar to Pandoravirus, the scientists initially thought that this was a new member - albeit certainly ancient - of this family.
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