Siphoviridae. Siphoviridae

Description of Siphoviridae adapted from ICTVdb Virion Properties Morphology Phages consist of a head and a tail and are not enveloped. Phage has a head with icosahedral symmetry and a tail with helical (tail) and icosahedral (head) symmetry (T=7). The head is isometric and has a diameter of 60 nm. Capsids appear hexagonal in outline. The capsid consists of 72 capsomers. The tail is non-contractile; is filamentous; is cross-banded with a length of (65-)150(-570) nm and a width of (7-)8(-10) nm. Tail has fibers; fibers are short; fibers are terminal and subterminal. Physicochemical and Physical Properties Virions have a buoyant density in CsCl of 1.46-1.56 g cm-3. Nucleic Acid The Mr of the genome constitutes 54% of the virion by weight. The genome is not segmented and contains a single molecule of linear double-stranded DNA. The complete genome is 48500 nucleotides long. The genome has a guanine + cytosine content of 52 %. Double stranded DNA is non-permuted; the genome sequence has termini with cohesive ends. Proteins The viral genome encodes structural proteins and non-structural proteins. Lipids Lipids are not reported.