Cystoviruses are a family of double-stranded RNA viruses that infect bacteria. They constitute the family Cystoviridae. The name of the group c ysto derives from Ancient 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–Lincoln. 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 present.
In 1999, phi7–14 were identified by the laboratory of Leonard Mindich at the Public Health Research Institute associated with New York University. They did this by culturing various leaves in Lysogeny Broth and then plating the broth on lawns of Pseudomonas syringae pv phaseolicola. They were able to identify from this and then subsequently sequence their genomes.
Microbiology
Structure
Cystovirus particles are
Viral envelope, with
Icosahedron 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 species, but this is likely biased due to the method of screening and enrichment.
However, cystoviruses do not only infect Pseudomonas. But also bacteria of the genera Streptomyces,[ Cystoviridae. NCBI Taxonomy.] and possibly other bacterial genera.
Taxonomy
The family contains the following genera and species (-
virus denotes genus):
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
External links
