title: Comparison of a Modern and Fossil Pithovirus Reveals Its Genetic Conservation and Evolution.
abstract: Most theories on viral evolution are speculative and lack fossil comparison. Here, we isolated a modern Pithovirus-like virus from sewage samples. This giant virus, named Pithovirus massiliensis, was compared with its prehistoric counterpart, Pithovirus sibericum, found in Siberian permafrost. Our analysis revealed near-complete gene repertoire conservation, including horizontal gene transfer and ORFans. Furthermore, all orthologous genes evolved under strong purifying selection with a non-synonymous and synonymous ratio in the same range as the ratio found in the prokaryotic world. The comparison between fossil and modern Pithovirus species provided an estimation of the cadence of the molecular clock, reaching up to 3 × 10(-6) mutations/site/year. In addition, the strict conservation of HGTs and ORFans in P. massiliensis revealed the stable genetic mosaicism in giant viruses and excludes the concept of a bag of genes. The genetic stability for 30,000 years of P. massiliensis demonstrates that giant viruses evolve similarly to prokaryotes by classical mechanisms of evolution, including selection and fixation of genes, followed by selective constraints.
authors.affiliation: Aix-Marseille Université, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS 7278, IRD 198, INSERM U1095, IHU Méditerranée Infection, Pôle des Maladies Infectieuses, Assistance Publique-Hôpitaux de Marseille, Faculté de Médecine, Marseille 13005, France.
authors.forename: Anthony
authors.initials: A
authors.lastname: Levasseur
authors.affiliation: Aix-Marseille Université, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS 7278, IRD 198, INSERM U1095, IHU Méditerranée Infection, Pôle des Maladies Infectieuses, Assistance Publique-Hôpitaux de Marseille, Faculté de Médecine, Marseille 13005, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Andreani
authors.affiliation: Aix-Marseille Université, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS 7278, IRD 198, INSERM U1095, IHU Méditerranée Infection, Pôle des Maladies Infectieuses, Assistance Publique-Hôpitaux de Marseille, Faculté de Médecine, Marseille 13005, France.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Delerce
authors.affiliation: Aix-Marseille Université, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS 7278, IRD 198, INSERM U1095, IHU Méditerranée Infection, Pôle des Maladies Infectieuses, Assistance Publique-Hôpitaux de Marseille, Faculté de Médecine, Marseille 13005, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Bou Khalil
authors.affiliation: Aix-Marseille Université, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS 7278, IRD 198, INSERM U1095, IHU Méditerranée Infection, Pôle des Maladies Infectieuses, Assistance Publique-Hôpitaux de Marseille, Faculté de Médecine, Marseille 13005, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Robert
authors.affiliation: Aix-Marseille Université, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS 7278, IRD 198, INSERM U1095, IHU Méditerranée Infection, Pôle des Maladies Infectieuses, Assistance Publique-Hôpitaux de Marseille, Faculté de Médecine, Marseille 13005, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: La Scola
authors.affiliation: Aix-Marseille Université, Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (URMITE), UM63, CNRS 7278, IRD 198, INSERM U1095, IHU Méditerranée Infection, Pôle des Maladies Infectieuses, Assistance Publique-Hôpitaux de Marseille, Faculté de Médecine, Marseille 13005, France didier.raoult@gmail.com.
authors.forename: Didier
authors.initials: D
authors.lastname: Raoult
mesh_terms: D019143:Evolution, Molecular; D005580:Fossils / Q000821:virology*; D022761:Gene Transfer, Horizontal; D016679:Genome, Viral / Q000235:genetics*; D000072139:Giant Viruses / Q000235:genetics*; D009030:Mosaicism; D010802:Phylogeny; D017422:Sequence Analysis, DNA
keywords: evolution; fossil; giant viruses; mosaicism