Experimental fossilisation of viruses from extremophilic Archaea
1Centre de Biophysique Moléculaire, CNRS, UPR 4301, Rue Charles Sadron, 45071 Orléans Cedex 2, France
2Observatoire des Sciences de l'Univers en région Centre, UMS 3116, 1A Rue de la Férollerie, 45071 Orléans Cedex 2, France
3Université de Bretagne Occidentale, CNRS – UMR 6539, Institut Universitaire Européen de la Mer, Technopôle Brest-Iroise, Rue Dumont d'Urville, 29280 Plouzané, France
4Molecular Biology of the Gene in Extremophiles Unit, Institut Pasteur, rue du Docteur Roux 25, 75724 Paris Cedex 15, France
Abstract. The role of viruses at different stages of the origin of life has recently been reconsidered. It appears that viruses may have accompanied the earliest forms of life, allowing the transition from an RNA to a DNA world and possibly being involved in the shaping of tree of life in the three domains that we know presently. In addition, a large variety of viruses has been recently identified in extreme environments, hosted by extremophilic microorganisms, in ecosystems considered as analogues to those of the early Earth. The earliest traces of life were preserved by the precipitation of silica on organic structures. The study of the in situ and experimental fossilisation of microorganisms allows better understanding of the fossilisation processes and helps identification of traces of life in ancient rocks. In a continuation of these studies, we present the results of the first experimental fossilisation by silica of viruses from extremophilic Archaea (SIRV2 – Sulfolobus islandicus Virus 2, TPV1 – Thermococcus prieurii virus 1, and PAV1 – Pyrococcus abyssi virus 1). Our results confirm that viruses can be fossilised, with silica precipitating on the different viral structures (proteins, envelope) over several months. However differences in the silicification process were noticed, depending on the viral structure and composition. The fossilisation mechanism is similar to that of the fossilisation of microorganisms. This study thus suggests that viral remains or traces could be preserved in the rock record although their identification may be challenging due to the small size of the viral particles.