La Scola B. auteur aut IRD Desnues C. auteur aut IRD Pagnier I. auteur aut IRD Robert C. auteur aut IRD Barrassi L. auteur aut IRD Fournous G. auteur aut IRD Merchat M. auteur aut IRD Suzan-Monti M. auteur aut IRD Forterre P. auteur aut IRD Koonin E. auteur aut IRD Raoult Didier auteur aut IRD text journalArticle eng text/pdf born digital access Viruses are obligate parasites of Eukarya, Archaea and Bacteria. Acanthamoeba polyphaga mimivirus ( APMV) is the largest known virus; it grows only in amoeba and is visible under the optical microscope. Mimivirus possesses a 1,185- kilobase double- stranded linear chromosome whose coding capacity is greater than that of numerous bacteria and archaea(1-3). Here we describe an icosahedral small virus, Sputnik, 50 nm in size, found associated with a new strain of APMV. Sputnik cannot multiply in Acanthamoeba castellanii but grows rapidly, after an eclipse phase, in the giant virus factory found in amoebae co- infected with APMV(4). Sputnik growth is deleterious to APMV and results in the production of abortive forms and abnormal capsid assembly of the host virus. The Sputnik genome is an 18.343- kilobase circular double- stranded DNA and contains genes that are linked to viruses infecting each of the three domains of life Eukarya, Archaea and Bacteria. Of the 21 predicted protein- coding genes, eight encode proteins with detectable homologues, including three proteins apparently derived from APMV, a homologue of an archaeal virus integrase, a predicted primase helicase, a packaging ATPase with homologues in bacteriophages and eukaryotic viruses, a distant homologue of bacterial insertion sequence transposase DNA- binding subunit, and a Zn- ribbon protein. The closest homologues of the last four of these proteins were detected in the Global Ocean Survey environmental data set(5), suggesting that Sputnik represents a currently unknown family of viruses. Considering its functional analogy with bacteriophages, we classify this virus as a virophage. The virophage could be a vehicle mediating lateral gene transfer between giant viruses. specialized 052 455 7209 100-NIL_65 2008 0028-0836 https://www.documentation.ird.fr/hor/fdi:010042763 10.1038/nature07218 0028-0836 [F B010042763] https://www.documentation.ird.fr/hor/fdi:010042763 https://www.documentation.ird.fr/intranet/publi/2008/09/010042763.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2008-10-06 2017-08-23 fdi:010042763 fre