Bicaudaviridae
Bicaudaviridae is a family of hyperthermophilic archaeal viruses that infect members of the genus Acidianus. The family contains one genus, Bicaudavirus, with a single species, Acidianus two-tailed virus (ATV). However, additional viruses, including Sulfolobus tengchongensis spindle-shaped viruses 1 and 2 (STSV1 and STSV2), are considered members of this family
Structure
Virions in the Bicaudaviridae family exhibit distinct structural and genomic features:
- Geometry: Lemon-shaped or spindle-shaped.
- Capsid: Non-enveloped, composed of a single major capsid protein.
- Symmetry: Helical, with continuous 7-start helices forming both the body and tails of the virion.
- Genome: Circular, double-stranded DNA (dsDNA) ranging from 48–76 kb in size.
- Comparative Structure: The capsid protein and virion architecture share similarities with viruses from the families Fuselloviridae, Thaspiviridae, Halspiviridae, and Clavaviridae.
Structural Studies
- High-resolution cryo-EM data is available for Sulfolobus monocaudavirus 1 (SMV1), while a lower-resolution structure has been determined for Acidianus two-tailed virus (ATV).
Life CyclE
- Host Range: Infects hyperthermophilic archaea, particularly from the order Sulfolobales.
- Replication:
- Replication occurs in the cytoplasm.
- Virions attach to host receptors and use DNA-templated transcription for genome expression.
- Transmission: Occurs via passive diffusion.
Notable Effects
- Certain family members, such as STSV2 and SMV1, cause cell gigantism by arresting the cell cycle at the S phase and blocking the expression of cell division genes.
- Infected cells exhibit a dramatic increase in size, with diameters growing up to 20 times larger, resulting in an 8,000-fold volume increase compared to uninfected cells.