The Siphoviridae reference article from the English Wikipedia on 24-Apr-2004
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Siphoviridae

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Siphoviridae is a family of double-stranded DNA viruses infecting only bacteria that are caracterized by a long non-contractile tail and an isometric capsid (morphotype B1) or a prolate capsid (morphotype B2).

The Viruses

The Siphoviridae viruses have a capsid with a diameter of about 55-60 nm and a long tail that can reach up to 570 nm. Their double-stranded DNA is linear. This family includes the viruses &lambda (lamda), &chi (chi) and &phi 80 (phi).