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A Viral Biorealm page on the family Siphoviridae

EM of a lambda phage, a member of the siphoviridae family. Image Courtesy Dr Maria Schnos, Department of Molecular Virology, Bock Laboratories, University of Wisconsin


Baltimore Classification

Higher order taxa

Viruses; dsDNA viruses, no RNA stage; Caudovirales; Siphoviridae


λ-like phages, T1-like viruses, T5-like viruses, L5-like viruses, c2-like viruses, ψM1-like viruses, φ 31-like viruses, N15-like viruses

Description and Significance

Genome Structure

The genome of siphoviridae is not segmented and contains a single molecule of linear double-stranded DNA. The complete genome is 48500 nucleotides long and the genome has a guanine + cytosine content of 52 %. The double-stranded DNA is not permuted and the genome sequence has termini with cohesive ends. (source: ICTVdB Descriptions)

Virion Structure of a Siphoviridae

The phages of a siphoviridae consist of a head and a tail and are not enveloped. The phage has a head with icosahedral symmetry and a tail with helical and icosahedral symmetry (T=7). The head is isometric and has a diameter of 60 nm. The capsids appear hexagonal in outline. The capsid consists of 72 capsomers. The tail is non-contractile and is filamentous. It is cross-branded with a length of about 150 nm and a width of about 8 nm. The tail has short fibers that are terminal and subterminal. (source: ICTVdB Descriptions)

Reproduction Cycle of a Siphoviridae in a Host Cell

Viral Ecology & Pathology


ICTVdB Descriptions

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