CryoEM model of Enterobacteria phage PRD1 capsid. PDB entry 1gw7[1]
Virus classification
Group: Group I (dsDNA)
Family: Tectiviridae
Genus: Tectivirus
Type species
Enterobacteria phage PRD1

Tectivirus is a genus of viruses, and is currently the only genus in the family Tectiviridae. Gram-negative bacteria serve as natural hosts. There are currently four species in this genus including the type species Enterobacteria phage PRD1.[2][3] Tectiviruses have no head-tail structure, but are capable of producing tail-like tubes of ~ 60×10 nm upon adsorption or after chloroform treatment. The name is derived from Latin tectus (meaning 'covered').


The virions of Tectiviridae species are non-enveloped, icosahedral and display a pseudo T=25 symmetry.[2] The capsid has two layers. The outer layer is a protein structure of 240 capsid proteins trimers, and the inner one is a proteinaceous lipid membrane which envelopes the virus genome. Apical spikes extending about 20 nanometers (nm) protrude from the icosahedrons vertices.

The genome is a single molecule of linear double-stranded DNA of 15 kilobases in length, and has 30 open reading frames.[2] It forms a tightly packed coil and encodes several structural proteins. It encodes about 30 proteins that are transcribed in operons. At least 9 structural proteins are present in the viron. The genome is about 66 megaDaltons in weight and constitutes 14–15% of the virion by weight. Lipids constitute a further 15% by weight. Carbohydrates are not present.

Genus Structure Symmetry Capsid Genomic Arrangement Genomic Segmentation

Life cycle

Viral replication is cytoplasmic. Entry into the host cell is achieved by adsorption into the host cell.[2] After adsorption to the host cell surface the virion extrudes a tail-tube structure through a vertex for genome delivery into the host. Replication follows the DNA strand displacement model. DNA-templated transcription is the method of transcription.[2] Capsid proteins polymerize around a lipoprotein vesicle translocated in the cytoplasm by virion assembly factors.

Mature virons are released by lysis, which, in the case of PRD1, is achieved with the aid of virus-encoded lysis machinery consisting of four proteins: P15 (endolysin),[4] P35 (holin),[5] P36 and P37 (homologues of the Rz/Rz1 proteins of phage lambda).[6]

Genus Host Details Tissue Tropism Entry Details Release Details Replication Site Assembly Site Transmission
TectivirusGram-negative bacteriaNoneInjectionLysisCytoplasmCytoplasmPassive diffusion


Group: dsDNA



  1. San Martín, C; Huiskonen, JT; Bamford, JK; Butcher, SJ; Fuller, SD; Bamford, DH; Burnett, RM (2002). "Minor proteins, mobile arms and membrane-capsid interactions in the bacteriophage PRD1 capsid". Nature Structural Biology. 9 (10): 756–63. doi:10.1038/nsb837. PMID 12219080.
  2. 1 2 3 4 5 "Viral Zone". ExPASy. Retrieved 15 June 2015.
  3. 1 2 ICTV. "Virus Taxonomy: 2014 Release". Retrieved 15 June 2015.
  4. Caldentey J, Hänninen AL, Bamford DH (1994). "Gene XV of bacteriophage PRD1 encodes a lytic enzyme with muramidase activity". Eur J Biochem. 225 (1): 341–346. doi:10.1111/j.1432-1033.1994.00341.x. PMID 7925454.
  5. Rydman PS, Bamford DH (2003). "Identification and mutational analysis of bacteriophage PRD1 holin protein P35". J Bacteriol. 185 (13): 3795–3803. doi:10.1128/JB.185.13.3795-3803.2003. PMC 161566Freely accessible. PMID 12813073.
  6. Krupovic M, Cvirkaite-Krupovic V, Bamford DH (2008). "Identification and functional analysis of the Rz/Rz1-like accessory lysis genes in the membrane-containing bacteriophage PRD1". Mol Microbiol. 68 (2): 492–503. doi:10.1111/j.1365-2958.2008.06165.x. PMID 18366440.

Further reading

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