The virus family Tectiviridae ( lat.tectus : covered) comprises only three genera Alphatectivirus , Betatectivirus and Gammatectivirus - the former genus Tectivirus has since been split up by the International Committee on Taxonomy of Viruses (ICTV). These are bacteriophages with a linear, double-stranded DNA genome and an icosahedral capsid with a diameter of 66 nm and consisting of 240 capsomeres ; the capsomeres consist of trimers of the capsid protein P3. The uncovered capsid has a fiber-like extension ( spike , peplomer ) about 20 nm long at the corners of the icosahedral symmetry , which is made up of two proteins (P2 and P5) and anchored to a penton protein at the base .
Inside (!) The capsid there is a lipid membrane vesicle, which consists of virus proteins and the lipid membrane of the host bacterium. To discharge the DNA genome, a tail-like tube of approx. 60 × 10 nm is everted through the capsid from the inner membrane vesicle (hence the name Tecti for the property of this "hidden" injection device ). This unusual structure of a membrane vesicle within an icosahedral capsid is shared by the Tevtiviridae with the family Corticoviridae . The genome is packaged in a coiled form within the membrane vesicle. The double-stranded DNA of the Tectiviridae is about 15 kBp in size and covalently linked to proteins at its 5 'ends ; the prototype of the family, the Enterobacteria phage PRD1 , codes for 25 virus proteins.
Species " Thermus Phage P37-14 " (official status revoked by ICTV, as gene sequence is missing)
See also NCBI.
particularities
The hosts of the Tectiviridae are mesophilic bacteria. Only the species Thermus Phage p37-14 infects thermophilic bacteria and can be found in volcanic springs and geysers .
Enterobacteria Phage PRD1 in particular shows very many similarities to members of the Adenoviridae with regard to the capsid structure (trimeric hexagonal capsomers, pentons, fibers) and the genome organization (linear dsDNA, so-called inverted terminal repeats , terminal proteins, DNA polymerase type B). These similarities indicate a common origin, ie they are based on homology. Both families were therefore placed in the same class Tectiliviricetes by the ICTV in March 2020 .
literature
CM Fauquet, MA Mayo et al .: Eighth Report of the International Committee on Taxonomy of Viruses , London, San Diego, 2004
David M. Knipe, Peter M. Howley, et al. (eds.): Fields' Virology , 4th Edition, Philadelphia 2001
↑ a b Céline Verheust, Nadine Fornelos, Jacques Mahillon: GIL16, a New Gram-Positive Tectiviral Phage Related to the Bacillus thuringiensis GIL01 and the Bacillus cereus pBClin15 Elements , in: J Bacteriol. 187 (6), March 2005, pp. 1966–1973, doi: 10.1128 / JB.187.6.1966-1973.2005 , PMC 1064052 (free full text).