title: Pithovirus sibericum, a new bona fide member of the "Fourth TRUC" club.
abstract: Nucleocytoplasmic large DNA viruses, or representatives of the proposed order Megavirales, include giant viruses of Acanthamoeba that were discovered over the last 12 years and are bona fide microbes. Phylogenies based on a few genes conserved amongst these megaviruses and shared by microbes classified as Eukarya, Bacteria, and Archaea, allowed for delineation of a fourth monophylogenetic group or "TRUC" (Things Resisting Uncompleted Classification) composed of the Megavirales representatives. A new Megavirales member named Pithovirus sibericum was isolated from a >30,000-year-old dated Siberian permafrost sample. This virion is as large as recently described pandoraviruses but has a genome that is approximately three to four times shorter. Our objective was to update the classification of P. sibericum as a new member of the "Fourth TRUC" club. Phylogenetic trees were constructed based on four conserved ancient genes and a phyletic analysis was concurrently conducted based on the presence/absence patterns of a set of informational genes from members of Megavirales, Bacteria, Archaea, and Eukarya. Phylogenetic analyses based on the four conserved genes revealed that P. sibericum is part of the fourth TRUC composed of Megavirales members, and is closely related to the families Marseilleviridae and Ascoviridae/Iridoviridae. Additionally, hierarchical clustering delineated four branches, and showed that P. sibericum is part of this fourth TRUC. Overall, phylogenetic and phyletic analyses using informational genes clearly indicate that P. sibericum is a new bona fide member of the "Fourth TRUC" club composed of representatives of Megavirales, alongside Bacteria, Archaea, and Eukarya.
authors: Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UM63, Centre National de la Recherche Scientifique 7278, IRD 198, Institut National de la Santé et de la Recherche Médicale U1095, Aix-Marseille University Marseille, France ; I2M UMR 7373, Centre National de la Recherche Scientifique Équipe Evolution Biologique et Modélisation, Aix-Marseille University Marseille, France.
authors: Vikas
authors: V
authors: Sharma
authors: Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UM63, Centre National de la Recherche Scientifique 7278, IRD 198, Institut National de la Santé et de la Recherche Médicale U1095, Aix-Marseille University Marseille, France ; Institut Hospitalo-Universitaire (IHU) Méditerranée Infection, Pôle des Maladies Infectieuses et Tropicales Clinique et Biologique, Fédération de Bactériologie-Hygiène-Virologie, Centre Hospitalo-Universitaire Timone, Assistance Publique-Hôpitaux de Marseille Marseille, France.
authors: Philippe
authors: P
authors: Colson
authors: I2M UMR 7373, Centre National de la Recherche Scientifique Équipe Evolution Biologique et Modélisation, Aix-Marseille University Marseille, France.
authors: Olivier
authors: O
authors: Chabrol
authors: I2M UMR 7373, Centre National de la Recherche Scientifique Équipe Evolution Biologique et Modélisation, Aix-Marseille University Marseille, France.
authors: Pierre
authors: P
authors: Pontarotti
authors: Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UM63, Centre National de la Recherche Scientifique 7278, IRD 198, Institut National de la Santé et de la Recherche Médicale U1095, Aix-Marseille University Marseille, France ; Institut Hospitalo-Universitaire (IHU) Méditerranée Infection, Pôle des Maladies Infectieuses et Tropicales Clinique et Biologique, Fédération de Bactériologie-Hygiène-Virologie, Centre Hospitalo-Universitaire Timone, Assistance Publique-Hôpitaux de Marseille Marseille, France.
authors: Didier
authors: D
authors: Raoult
keywords: Megavirales; Pithovirus sibericum; TRUC; domains of life; giant virus; informational genes; nucleocytoplasmic large DNA viruses; phylogeny