Virophage
Lavidaviridae | |
---|---|
Sputnik virophage | |
Virus classification | |
(unranked): | Virus |
Realm: | Varidnaviria |
Kingdom: | Bamfordvirae |
Phylum: | Preplasmiviricota |
Class: | Maveriviricetes |
Order: | Priklausovirales |
Family: | Lavidaviridae |
Genera and species | |
|
Virophages are small, double-stranded DNA viral phages that require the co-infection of another virus. The co-infecting viruses are typically giant viruses. Virophages rely on the viral replication factory of the co-infecting giant virus for their own replication. One of the characteristics of virophages is that they have a parasitic relationship with the co-infecting virus. Their dependence upon the giant virus for replication often results in the deactivation of the giant viruses. The virophage may improve the recovery and survival of the host organism.
All known virophages are grouped into the family Lavidaviridae (from "large virus dependent or associated" + -viridae).[2]
Discovery
The first virophage was discovered in a
A majority of these virophages are being discovered by analyzing metagenomic data sets. In metagenomic analysis, DNA sequences are run through multiple bioinformatic algorithms which pull out certain important patterns and characteristics. In these data sets are giant viruses and virophages. They are separated by looking for sequences around 17 to 20 kbp long which have similarities to already sequenced virophages. These virophages can have linear or circular double-stranded DNA genomes.[7] Known virophages in culture have icosahedral capsid particles that measure around 40 to 80 nanometers long,[8] and virophage particles are so small that electron microscopy must be used to view them. Metagenomic sequence-based analyses have been used to predict around 57 complete and partial virophage genomes[9] and in December 2019 to identify 328 high-quality (complete or near-complete) genomes from diverse habitats including the human gut, plant rhizosphere, and terrestrial subsurface, from 27 distinct taxonomic clades.[10]
Host range and replication
Virophages need to have a co-infecting virus in order for them to replicate. The virophages do not have the necessary enzymes to replicate on their own. Virophages use the giant viral replication machinery to replicate their own genomes and continue their existence. The host range for virophages include giant viruses with double stranded DNA genomes. Virophages use the transcriptional machinery of these giant viruses for their own replication instead of the host's transcriptional machinery. For example, the discovery of the virophage associated with the Samba virus decreased the viruses concentration in the host while the virophage was replicating using the giant virus. The host amoeba also showed a partial recovery from the infection by the Samba virus.[7]
Genome
Virophages have small double-stranded DNA
Genome
Size (kbp) |
Particle Size
(diameter, in nm) | |
---|---|---|
Virus: Poliovirus | 7 | 30 |
Virus: Adenoviridae | 26–48 | 90–100 |
Virophage: Zamilon Virophage | 17 | 50–60 |
Virophage: Sputnik Virophage | 18 | 74 |
Giant virus: Cafeteria roenbergensis virus | 700 | 75 |
Giant virus: Mimivirus | 1,181 | 400–800 |
All virophages known so far have four core genes. They are the virophage-specific major and minor
Taxonomy
The family Lavidaviridae with the two genera, Sputnikvirus and Mavirus, has been established by the International Committee on Taxonomy of Viruses for classification of virophages. It is the sole family under order Priklausovirales (from Lithuanian priklausomas, "dependent"), which in turn is the sole order under class Maveriviricetes (from Maverick transposons).[8][12]
- Family Lavidaviridae
- Genus Sputnikvirus
- Species Mimivirus-dependent virus Sputnik
- Species Mimivirus-dependent virus Zamilon
- Species
- Genus Mavirus
- Species Cafeteriavirus-dependent mavirus
- Species
- Genus
- Unassigned genus
Additionally, virophage genomes identified from metagenomes have been classified together with the isolate virophages into 27 distinct clades with consistent genome length, gene content, and habitat distribution.[10] Some fragmentary virophage sequences were additionally reported in a Loki's Castle metagenome.[13]
References
- ^ doi:10.3390/v11080733. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License
- PMID 30897185.
- S2CID 206530677.
- S2CID 4458402.
- ^ taxonomy. "Taxonomy browser (Lavidaviridae)". www.ncbi.nlm.nih.gov. Retrieved 2023-09-20.
- ^ taxonomy. "Taxonomy browser (Preplasmiviricota)". www.ncbi.nlm.nih.gov. Retrieved 2023-09-20.
- ^ PMID 25184667.
- ^ S2CID 14196910– via Springer.
- ^ PMID 29021524.
- ^ PMID 31823797.
- PMID 29941605.
- .
- doi:10.1371/journal.ppat.1007592. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.