Fuselloviridae
Fuselloviridae is a family of viruses that predominantly infect archaea, with Sulfolobus species such as Sulfolobus shibatae, Sulfolobus solfataricus, and Sulfolobus islandicus serving as their natural hosts. The family comprises two genera and nine species. Fuselloviruses are commonly found in extreme environments, particularly in high-temperature (≥70°C), acidic (pH ≤4) hot springs around the world, where they thrive.
Structure of Fuselloviridae Virions
Virions in the Fuselloviridae family are enveloped with lemon-shaped geometries, typically measuring around 60 nm in diameter and 100 nm in length. Their genomes consist of double-stranded circular DNA, with a length of approximately 17.3 kb. The prototypical fusellovirus, SSV1, has been extensively studied for its biochemical properties, revealing that the virions are composed of four virus-encoded structural proteins: VP1 to VP4. Additionally, there is one DNA-binding chromatin protein of cellular origin.
Protein Modifications and Lipid Composition
The viral proteins VP1, VP3, and VP4 undergo posttranslational modifications, including glycosylation at multiple sites. Moreover, VP1 is proteolytically processed. A distinctive feature of SSV1 virions is the presence of glycerol dibiphytanyl glycerol tetraether (GDGT) lipids, which are selectively acquired from the host’s cytoplasmic membrane. These lipids play a crucial role in the virion's structure and its ability to adapt to the extreme environments in which these viruses thrive.
Genus | Structure | Symmetry | Capsid | Genomic arrangement | Genomic segmentation |
|---|---|---|---|---|---|
| Alphafusellovirus | Lemon-shaped | Enveloped | Circular | Monopartite | |
| Betafusellovirus | Lemon-shaped | Enveloped | Circular | Monopartite |