title: Virion architecture unifies globally distributed pleolipoviruses infecting halophilic archaea.
abstract: Our understanding of the third domain of life, Archaea, has greatly increased since its establishment some 20 years ago. The increasing information on archaea has also brought their viruses into the limelight. Today, about 100 archaeal viruses are known, which is a low number compared to the numbers of characterized bacterial or eukaryotic viruses. Here, we have performed a comparative biological and structural study of seven pleomorphic viruses infecting extremely halophilic archaea. The pleomorphic nature of this novel virion type was established by sedimentation analysis and cryo-electron microscopy. These nonlytic viruses form virions characterized by a lipid vesicle enclosing the genome, without any nucleoproteins. The viral lipids are unselectively acquired from host cell membranes. The virions contain two to three major structural proteins, which either are embedded in the membrane or form spikes distributed randomly on the external membrane surface. Thus, the most important step during virion assembly is most likely the interaction of the membrane proteins with the genome. The interaction can be driven by single-stranded or double-stranded DNA, resulting in the virions having similar architectures but different genome types. Based on our comparative study, these viruses probably form a novel group, which we define as pleolipoviruses.
authors.affiliation: Institute of Biotechnology and Department of Biosciences, University of Helsinki, Helsinki, Finland.
authors.forename: Maija K
authors.initials: MK
authors.lastname: Pietilä
authors.forename: Nina S
authors.initials: NS
authors.lastname: Atanasova
authors.forename: Violeta
authors.initials: V
authors.lastname: Manole
authors.forename: Lassi
authors.initials: L
authors.lastname: Liljeroos
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Butcher
authors.forename: Hanna M
authors.initials: HM
authors.lastname: Oksanen
authors.forename: Dennis H
authors.initials: DH
authors.lastname: Bamford
mesh_terms: D001105:Archaea / Q000821:virology*; D023641:Archaeal Viruses / Q000502:physiology* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry; D012336:RNA, Ribosomal, 16S / Q000737:chemistry; D014759:Viral Envelope Proteins / Q000737:chemistry; D014771:Virion / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure
chemical_list: D012336:RNA, Ribosomal, 16S; D014759:Viral Envelope Proteins; D010447:Peptide Hydrolases