Cystoviruses are a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of double-stranded RNA viruses that infect

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

. They constitute the family ''Cystoviridae''. The name of the group c''ysto'' derives from Greek ''kystis'' which means bladder or sack. There are seven genera in this family.

Discovery

Pseudomonas virus phi6 was the first virus in this family to be discovered and was initially characterized in 1973 by Anne Vidaver at the

University of Nebraska A university () is an educational institution, institution of tertiary education and research which awards academic degrees in several Discipline (academia), academic disciplines. ''University'' is derived from the Latin phrase , which roughly ...

. She found that when she cultured the bacterial strain '' Pseudomonas phaseolicola'' HB1OY with halo blight infected bean straw, cytopathic effects were detected in cultured lawns, indicating that there was a lytic microbe or

bacteriophage A bacteriophage (), also known informally as a phage (), is a virus that infects and replicates within bacteria. The term is derived . Bacteriophages are composed of proteins that Capsid, encapsulate a DNA or RNA genome, and may have structu ...

present. In 1999, phi7–14 were identified by the laboratory of Leonard Mindich at the Public Health Research Institute associated with

New York University New York University (NYU) is a private university, private research university in New York City, New York, United States. Chartered in 1831 by the New York State Legislature, NYU was founded in 1832 by Albert Gallatin as a Nondenominational ...

. They did this by culturing various leaves in

Lysogeny Broth Lysogeny broth (LB) is a Nutrient, nutritionally rich Growth medium, medium primarily used for the Bacterial growth, growth of bacteria. Its creator, Giuseppe Bertani, intended LB to stand for lysogeny broth, but LB has also come to colloquially ...

and then plating the broth on lawns of '' Pseudomonas syringae pv phaseolicola''. They were able to identify viral plaques from this and then subsequently sequence their genomes.

Microbiology

Structure

Cystovirus particles are enveloped, with icosahedral and spherical geometries, and T=13, T=2 symmetry. The virion diameter is around 85 nm.

Genome

Cystoviruses have a tripartite double-stranded RNA genome which is approximately 14 kbp 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.

Life cycle

Cystoviruses enter the bacteria by adsorption on its pilus 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 by lysis. Most identified cystoviruses infect ''

Pseudomonas ''Pseudomonas'' is a genus of Gram-negative bacteria belonging to the family Pseudomonadaceae in the class Gammaproteobacteria. The 348 members of the genus demonstrate a great deal of metabolic diversity and consequently are able to colonize a ...

'' species, but this is likely biased due to the method of screening and enrichment. There are many proposed members of this family. Pseudomonas viruses φ7, φ8, φ9, φ10, φ11, φ12, and φ13 have been identified and named, but other cystovirus-like viruses have also been isolated. These seven putative relatives are classified as either close (φ7, φ9, φ10, φ11) or distant (φ8, φ12, φ13) relatives to φ6, with the distant relatives thought to infect via the LPS rather than the pili. However, cystoviruses do not only infect ''Pseudomonas''. But also bacteria of the genera '' Streptomyces'', '' Microvirgula'', '' Acinetobacter'', '' Lactococcus'', '' Pectobacterium'',Cystoviridae
NCBI Taxonomy. and possibly other bacterial genera.

Taxonomy

The family contains the following genera and species (-''virus'' denotes genus): * '' Alphacystovirus'' ** '' Alphacystovirus phi8'' * '' Betacystovirus'' ** '' Betacystovirus phi12'' * '' Deltacystovirus'' ** '' Deltacystovirus phi2954'' * '' Epsiloncystovirus'' ** '' Epsiloncystovirus phiNY'' * '' Gammacystovirus'' ** '' Gammacystovirus phi13'' ** '' Gammacystovirus phiYY'' * '' Orthocystovirus'' ** '' Orthocystovirus phi6'' ** '' Orthocystovirus phiNN'' * '' Zetacystovirus'' ** '' Zetacystovirus CAP'' Other unassigned phages: * Streptomyces virus phi0 * Lactococcus virus phi7-4 * Pectobacterium virus MA14 * Acinetobacter virus CAP3 * Acinetobacter virus CAP4 * Acinetobacter virus CAP5 * Acinetobacter virus CAP6 * Acinetobacter virus CAP7

References

External links

ICTV Online Report: ''Cystoviridae''

{{Authority control Cystoviridae Riboviria Virus families