Tectivirus
The Tectiviridae is a family of double-stranded DNA viruses that infect bacteria and archea. Tectiviridae have no head-tail structure, but are capable of producing tail-like tubes of ~ 60 x 10 nm upon adsorption or after chloroform treatment. The name is derived from Latin tectus (meaning 'covered').
There is a single genus in this family - genus Tectivirus.
The type species is Enterobacteria phage PRD1.
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[edit] Virology
This family of viruses consist of virons with double layers capsids that have apical spikes extending ~20 nanometers (nm) and an unusual internal lipid envelope around the nucleoprotein.
The capsid is nonenveloped and has a diameter of 63 nm icosahedron structure. The capsid shells are composed of two layers - an inner and outer capsid.
The inner capsid shell consist of a 5-6 nm flexible shell made from a lipoprotein vesicle, whereas the outer capsid is made up of a smooth, rigid 3 nm thin protein shell. The outer shell has a pseudo T = 25 symmetry and consists of 240 capsid proteins trimers.
The genome is a single molecule of linear double-stranded DNA of 15 kilobases in length. It forms a tightly packed coil and encodes several structural proteins. It encodes ~30 proteins that are transcribed in operons.
At least 9 structural proteins are present in the viron.
The genome is ~66 megaDaltons in weigh and constitutes 14-15% of the virion by weight. Lipids constitute a further 15% by weight. Carbohydrates are not present.
[edit] Life cycle
After adsorbion to the host's cells surface the viron extruds a tail-tube structure through a vertex for genome delivery into the host.
Capsid proteins polymerize around a lipoprotein vesicle translocated in the cytoplasm by virion assembly factors.
Mature virons are released by lysis.
[edit] References
ICTVdB - The Universal Virus Database ICTVdB Management (2006). 00.068. Tectiviridae. In: ICTVdB - The Universal Virus Database, version 3. Büchen-Osmond, C. (Ed), Columbia University, New York, USA
Virus Taxonomy: Eighth Report of the International Committee on Taxonomy of Viruses H.V. Van Regenmortel, D.H.L. Bishop, M. H. Van Regenmortel, Claude M. Fauquet (Eds)
