Viruses infecting archaea show a variety of virion morphotypes, and they are currently classified into more than ten viral families or corresponding groups. A pleomorphic virus morphotype is very common among haloarchaeal viruses, and to date, several such viruses have been isolated. Here, we propose the classification of eight such viruses and formation of a new family, Pleolipoviridae (from the Greek pleo for more or many and lipos for lipid), containing three genera, Alpha-, Beta-, and Gammapleolipovirus. The proposal is currently under review by the International Committee on Taxonomy of Viruses (ICTV). The members of the proposed family Pleolipoviridae infect halophilic archaea and are nonlytic. They share structural and genomic features and differ from any other classified virus. The virion of pleolipoviruses is composed of a pleomorphic membrane vesicle enclosing the genome. All pleolipoviruses have two major structural protein species, internal membrane and spike proteins. Although the genomes of the pleolipoviruses are single- or double-stranded, linear or circular DNA molecules, they share the same genome organization and gene synteny and show significant similarity at the amino acid level. The canonical features common to all members of the proposed family Pleolipoviridae show that they are closely related and thus form a new viral family.

Department of Biosciences and Institute of Biotechnology University of Helsinki P O Box 56 Viikinkaari 9 00014 Helsinki Finland

Department of Food and Environmental Sciences University of Helsinki P O Box 56 Viikinkaari 9 00014 Helsinki Finland

Laboratory of Molecular Biology of Bacterial Pathogens Institute of Microbiology of the ASCR v v i Czech Academy of Sciences 142 20 Prague 4 Czech Republic

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ICTV Virus Taxonomy Profile: Pleolipoviridae

Bacteriophages and its applications: an overview