Archaeal viruses

Adnaviria is a realm of archaeal viruses that have filamentous virions (i.e., bodies) and linear, double-stranded DNA genomes. Their genomes exist in A-form (A-DNA) and encode a dimeric major capsid protein (MCP) that contains the SIRV2 fold, an alpha-helix bundle with four helices. Adnavirians infect hyperthermophilic (very high temperature), thermoacidophilic (high temperature, highly acidic), and methanotrophic (methane-metabolizing) archaea. They can be found worldwide, though some are concentrated in extreme geothermal environments.

Ligamenvirales is an order of linear viruses that infect archaea of the phylum Thermoproteota (formerly Crenarchaeota) and have double-stranded DNA genomes. The order was proposed by David Prangishvili and Mart Krupovic in 2012 and subsequently created by the International Committee on Taxonomy of Viruses (ICTV).

Fuselloviridae is a family of viruses. Sulfolobus species, specifically shibatae, solfataricus, and islandicus, serve as natural hosts. There are two genera in the family. Viruses in Fuselloviridae are ubiquitous in high-temperature (≥70 °C), acidic (pH ≤4) hot springs around the world.

Guttaviridae is a family of viruses. Archaea serve as natural hosts. The name is derived from the Latin gutta, meaning 'droplet'. The family contains one genus, Alphaguttavirus, which contains one species: Aeropyrum pernix ovoid virus 1 (Betaguttavirus kodakarajimaense).

thumb|Tailed bacteriophage structure: (1) head, (2) tail, (3) DNA, (4) capsid, (5) collar, (6) sheath, (7) tail fibres, (8) spikes, (9) base plate thumb|Transmission electron microscopy|Transmission electron micrograph of Gamma-Phage thumb|right|Illustrations of various caudoviricetes. Not to scale.

REDIRECT Alphasphaerolipovirus

Bottigliavirus is the only genus in the family Ampullaviridae and contains 3 species. Ampullaviridae infect archaea of the genus Acidianus. The name of the family and genus is derived from the Latin word for bottle, ampulla, due to the virions having the shape of a bottle. The family was first described during an investigation of the microbial flora of hot springs in Italy.

Bicaudaviridae is a family of hyperthermophilic archaeal viruses. Members of the genus Acidianus serve as natural hosts. There is only one genus, Bicaudavirus, and one species, Acidianus two-tailed virus (Bicaudavirus pozzuoliense), in this family. However, Sulfolobus tengchongensis spindle-shaped viruses 1 and 2 (STSV1 and STSV2) are regarded to belong to this family also.