| Cystovirus | |
|---|---|
 | |
 | |
| Pseudomonas phage phi6 particle, reconstruction, and genome | |
Virus classification | |
| (unranked): | Virus |
| Realm: | Riboviria |
| Kingdom: | Orthornavirae |
| Phylum: | Duplornaviricota |
| Class: | Vidaverviricetes |
| Order: | Mindivirales |
| Family: | Cystoviridae |
| Genus: | Cystovirus |
| Species | |
Cystovirus is a genus ofdouble-stranded RNA viruses which infectsbacteria. It is the only genus in the familyCystoviridae. The name of the group cysto derives fromGreekkystis which means bladder or sack. There are seven species in this genus.[1][2][3]
Pseudomonas virus phi6 was the first virus in this family to be discovered and was initially characterized in 1973 by Anne Vidaver at theUniversity of Nebraska. She found that when she cultured the bacterial strainPseudomonas phaseolicola HB1OY withhalo blight infected bean straw, cytopathic effects were detected in cultured lawns, indicating that there was a lytic microbe orbacteriophage present.[4]
In 1999, phi7–14 were identified by the laboratory of Leonard Mindich at the Public Health Research Institute associated withNew York University. They did this by culturing various leaves inLysogeny Broth and then plating the broth on lawns ofPseudomonas syringae pv phaseolicola. They were able to identifyviral plaques from this and then subsequently sequence their genomes.[5]
Cystovirus particles areenveloped, withicosahedral and spherical geometries, and T=13, T=2 symmetry. The virion diameter is around 85 nm. Cystoviruses are distinguished by their outer layerprotein andlipid envelope. No otherbacteriophage has any lipid in its outer coat, though theTectiviridae and theCorticoviridae have lipids within theircapsids.[1][2]
Cystoviruses have a tripartite double-stranded RNA genome which is approximately 14kbp in total length. The genome is linear and segmented, and labeled as large (L) 6.4 kbp, medium (M) 4 kbp, and small (S) 2.9 kb in length. The genome codes for twelve proteins.[1][2]
Cytoviruses enter the bacteria by adsorption on itspilus and then membrane fusion. Viral replication is cytoplasmic. Replication follows the double-stranded RNA virus replication model. Double-stranded RNA virus transcription is the method of transcription. The progeny viruses are released from the cell bylysis.[1][2]
Most identified cystoviruses infectPseudomonas species, but this is likely biased due to the method of screening and enrichment.[6] There are many proposed members of this family. Pseudomonas viruses φ7, φ8, φ9, φ10, φ11, φ12, and φ13 have been identified and named,[5] but other cystovirus-like viruses have also been isolated.[6] These seven putative relatives are classified as either close (φ7, φ9, φ10, φ11) or distant (φ8, φ12, φ13) relatives to φ6,[5] with the distant relatives thought to infect via theLPS rather than the pili.[7]
However, cystoviruses do not only infectPseudomonas. But also bacteria of the generaStreptomyces,[8]Microvirgula,[9]Acinetobacter,[10]Lactococcus,Pectobacterium,[11] and possibly other bacterial genera.
Members of theCystoviridae appear to be most closely related to theReoviridae,[12] but also sharehomology with theTotiviridae. In particular, the structural genes of cystoviruses are highly-similar to those used by a number of dsRNA viruses that infect eukaryotes.[13] The genusCystovirus has seven species:[1]
Other unassigned phages:
