''Halspiviridae'' is a family of viruses that consists of a single genus, ''Salterprovirus'', which consists of a single recognised species; ''Salterprovirus His1'' (hereafter, 'His1'). This virus was isolated from hypersaline water in Australia and was able to be cultured on the halophilic

archaeon Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebact ...

Haloarcula hispanica ''Haloarcula'' (common abbreviation ''Har.'') is a genus of extreme halophilic Archaeon, Archaea in the class of Halobactaria. Cell Structure ''Haloarcula'' species can be distinguished from other genera in the family Halobacteriaceae by the pre ...

''. Like many other archaeoviruses, His1 has an approximately limoniform (lemon-shaped)

virion A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's ...

Etymology

The family name, ''Halspiviridae'', is derived from halophilic and spindle-shaped, in reference to the habitat and virion morphology, respectively. The genus name, ''Salterprovirus'', is derived from salty terminal protein virus, as the linear dsDNA genome has proteins attached to the 5′ termini.

Taxonomy

The virion has a spindle-shaped morphology and is similar in shape to that of viruses infecting thermophilic archaea, the ''

Fuselloviridae ''Fuselloviridae'' is a family of viruses. Sulfolobus species, specifically shibatae, solfataricus, and islandicus, serve as natural hosts. There are two genera and nine species in the family. The ''Fuselloviridae'' are ubiquitous in high-tempe ...

'', and His1 was originally described as a probable member of that group. However, it was later found that there is no genetic relationship and their replication strategies are entirely different, and so His1 was classified into a new group, genus ''Salterprovirus'' within the family ''Halspiviridae''. ''Halspiviridae'' has not been classified within any higher-ranked taxa. Environmental DNA sequences derived from

Namib The Namib ( ; pt, Namibe) is a coastal desert in Southern Africa. The name is of Khoekhoegowab origin and means "vast place". According to the broadest definition, the Namib stretches for more than along the Atlantic coasts of Angola, Nami ...

salt pans indicate the presence of currently unrecognised, distant relatives of His1. Another species of virus, now named '' Gammapleolipovirus His2'' (hereafter 'His2'), was originally considered to be related to His1, but later analysis of the His2 virion revealed that this species actually belongs to the family ''

Pleolipoviridae ''Pleolipoviridae'' is a family of DNA virus A DNA virus is a virus that has a genome made of deoxyribonucleic acid (DNA) that is replicated by a DNA polymerase. They can be divided between those that have two strands of DNA in their genome, ...

''.

Structure

The virus is enveloped, with limoniform or spindle-shaped morphology. Genomes are linear, around 14.5kb in length. The genome has 35 open reading frames. A negatively stained electron microscope (EM) picture of His1 virions is shown on the right of this page. There is some variation in particle length (e.g. example seen left of centre), but most display the typical limoniform capsid with a short tail. High resolution micrographs and cryoEM reconstructions have been published by Hong et al. (2015), who gave average dimensions of 92 x 40 nm with a 12 nm tail.

Replication cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by virus attachment to the host cell. An adsorption rate constant for His1 of 1.9 x 10⁻¹² ml min⁻¹ has been experimentally determined by Pietilä et al. (2013). DNA-templated transcription is the method of transcription. ''Haloarcula hispanica'' may serve as a host. Transmission occurs via passive diffusion.

Genome

The linear, dsDNA genome of His1 consists o
14,464 base-pairs
(bp), has imperfect inverted terminal repeat sequences of 105 bp, and is annotated to carry 35 protein coding genes, including a gene specifying a protein-primed DNA polymerase (B-family). The ends of the genome have a protein attached. The protein sequence of the polymerase is 42% identical to the polymerase specified by the gammapleolipovirus His2, even though the two viruses belong to very different taxonomic groups.

References

External links

International Committee on Taxonomy of Viruses (ICTV)
{{Taxonbar, from=Q7406092 Double-stranded DNA viruses Virus genera Virus families