Cystovirus

The Cystoviridae are a family of enveloped virus RNA viruses with segmented double-stranded genome. The family currently includes only the genus Cystovirus. As a bacteriophage it uses different Gram- negative bacteria as host.

Cystoviren are the only Bakteriophagenfamilie with a complete viral envelope and the only one with RNA -based genome. The families of the Tectiviridae and Corticoviridae have indeed included lipids in their capsids, but no outer viral envelope.

The Cystoviren family seems closest to be related to the Reoviridae, but also possess homologies to the Totiviridae. This Cystoviren are the only family of bacteriophages, which are more closely related to viruses of eukaryotes, as with other phages.

Genome

The Cystoviren have three genomic segments of 2.9 kilobases (S segment), 4 kilobases ( M segment ) and 6.4 kilobases (L segment). The genome encodes 12 proteins. Most identified Cystoviren infect Pseudomonas species, and this may be due to the examination and enrichment method. The Φ6, Φ7, Φ8, Φ9, Φ10, Φ11, Φ12 and Φ13 were characterized and named more have only been isolated.

During tropism for some Cystoviren as Φ6 is determined by the binding of the multimeric protein P3 to type IV pili as receptor to use Φ8, Φ12 and Φ13, a heterodimeric protein that binds to lipopolysaccharide.

The protein P6 mediates fusion with the cell membrane of the host cell and the subsequent infiltration of the nucleocapsid without unpacking the RNA. P5 is a hydrolytic enzyme to dissolve the bacterial proteoglycan layer. P2 provides the RNA dependent RNA polymerase for the replication of the genome within the nucleocapsid. P4 promoted the single-stranded viral RNA segments of positive polarity with ATP consumption in the newly synthesized capsid proteins, where they are complemented by P2 to the double-stranded RNA. The cell is then left by lysis.