Phycodnaviridae

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Phycodnaviruses
Virus classification
Group: Group I (dsDNA)
Order: Unassigned
Family: Phycodnaviridae
Genera

Phycodnaviridae is a family of large (160 to 560 thousand base pairs), double stranded DNA viruses that infect marine or freshwater eukaryotic algae. They belong to a super-group of large viruses known as nucleocytoplasmic large DNA viruses (NCLDVs).

Virology[edit]

Phycodnaviruses have icosahedral morphology, an internal lipid membrane and replicate, completely or partly, in the cytoplasm of their host cells. The genomes range in size from 100 kilobases (kb) to >550 kb with G+C content between 40% and 50%.

Taxonomy[edit]

The taxonomy of this family was initially based on the host range: chloroviruses infect chlorella-like green algae from terrestrial waters, whereas members of the other five genera infect marine green and brown algae. This was subsequently confirmed by analysis of their DNA polymerases.[1]

Molecular biology[edit]

Recent studies have revealed features in Phycodnavirus genomes such as sophisticated replication and transcription machineries, a novel type of potassium channel protein, genes involved in inducing apoptosis in the host genome, a sophisticated signal transduction and gene regulation system and genes for glycosylation of viral proteins.

All phycodnaviruses encode a number of proteins involved in DNA replication or recombination, including a DNA-directed DNA polymerase. It is unclear if any phycodnaviruses encode a fully functional replication machinery, however. They are thought to rely on host enzymes at least partially.

Pathology[edit]

Until recently phycodnaviruses were believed to infect algal species exclusively. Recently, DNA homologous to Chlorovirus Acanthocystis turfacea virus 1 (ATCV-1) were isolated from human nasopharyngeal mucosal surfaces. The presence of ATCV-1 in the human microbiome was associated with diminished performance on cognitive assessments. Inoculation of ATCV-1 in experimental animals was associated with decreased performance in memory and sensory-motor gating, as well as altered expression of genes in the hippocampus related to synaptic plasticity, learning, memory formation, and the viral immune response.[2]

Evolution[edit]

Phycodnaviruses of viruses evolved from the Iridoviridae family of viruses.[3]

References[edit]

  1. ^ Anonymous (2012) Virus Taxonomy: IXth report of the international committee on taxonomy of viruses. Amsterdam: Academic Press p261
  2. ^ Yolken RH et al (2014) Chlorovirus ATCV-1 is part of the human oropharyngeal virome and is associated with changes in cognitive functions in humans and mice. Proc Natl Acad Sci U S A. 2014 Oct 27. pii: 201418895. [Epub ahead of print]
  3. ^ Wilson WH, Van Etten JL, Allen MJ (2009) The Phycodnaviridae: the story of how tiny giants rule the world. Curr Top Microbiol Immunol 328:1-42

Additional reading[edit]

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