RESUMO
Viruses infecting hyperthermophilic archaea of the phylum Crenarchaeota display enormous morphological and genetic diversity, and are classified into 12 families. Eight of these families include only one or two species, indicating sparse sampling of the crenarchaeal virus diversity. In an attempt to expand the crenarchaeal virome, we explored virus diversity in the acidic, hot spring Umi Jigoku in Beppu, Japan. Environmental samples were used to establish enrichment cultures under conditions favouring virus replication. The host diversity in the enrichment cultures was restricted to members of the order Sulfolobales. Metagenomic sequencing of the viral communities yielded seven complete or near-complete double-stranded DNA virus genomes. Six of these genomes could be attributed to polyhedral and filamentous viruses that were observed by electron microscopy in the enrichment cultures. Two icosahedral viruses represented species in the family Portogloboviridae. Among the filamentous viruses, two were identified as new species in the families Rudiviridae and Lipothrixviridae, whereas two other formed a group seemingly distinct from the known virus genera. No particle morphotype could be unequivocally assigned to the seventh viral genome, which apparently represents a new virus type. Our results suggest that filamentous viruses are globally distributed and are prevalent virus types in extreme geothermal environments.
Assuntos
Archaea/virologia , Vírus de Archaea/isolamento & purificação , Bacteriófagos/isolamento & purificação , Fontes Termais/virologia , Rudiviridae/genética , Rudiviridae/isolamento & purificação , Archaea/genética , Archaea/isolamento & purificação , Vírus de Archaea/classificação , Vírus de Archaea/genética , Vírus de Archaea/fisiologia , Bacteriófagos/classificação , Bacteriófagos/genética , Bacteriófagos/fisiologia , Genoma Viral , Fontes Termais/química , Japão , Lipothrixviridae/classificação , Lipothrixviridae/genética , Lipothrixviridae/isolamento & purificação , Lipothrixviridae/fisiologia , Metagenoma , Filogenia , Rudiviridae/classificação , Replicação ViralRESUMO
Linear viruses with double-stranded DNA genomes are classified into two families, Lipothrixviridae and Rudiviridae. The members of these two families, all of which infect hyperhermophilic members of the domain Archaea, differ significantly in the complexity of their virions as well as in their mechanisms of genome replication. However, recent structural and genomic studies have revealed a robust evolutionary link between members of the two families. To acknowledge this relationship we propose to unify the two families into the new taxonomic order "Ligamenvirales".