Virophage
Virophages are small, double-stranded DNA viral phages that require the co-infection of another virus.
It was discovered with its co-infecting giant virus, Acanthamoeba castellanii mamavirus (ACMV).
In metagenomic analysis, DNA sequences are run through multiple bioinformatic algorithms which pull out certain important patterns and characteristics.
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.
The host range for virophages include giant viruses with double stranded DNA genomes.
[7] Virophages have small double-stranded DNA genomes that are either circular or linear in shape.
[8] In contrast, their co-infecting giant virus counterparts can have genomes as large as 1–2 Mbp (megabasepairs).
[11] 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.
(B) When the host cell is co-infected with a giant virus and its virophage, the latter parasitizes the giant virus factory. The presence of virophages could seriously impact the infectivity of the giant virus by decreasing its replication efficiency and increasing the survival of the host cell.
(C) When the giant virus genome is parasitized by a provirophage, the latter is expressed during the giant virus replication. The virophage is produced from the giant virus factory and inhibits the giant virus replication, thus increasing the host cell survival.
(B) The concept of satellite virus implicates that the virus initiates the expression and replication of its genome in the nucleus using the host cell machinery and then goes to the cytoplasm. In the cytoplasm, the satellite virus hijacks the morphogenesis machinery of its helper virus to produce its progeny.
