see text Siphoviridae was a family of double-stranded DNA viruses in the order Caudovirales.
[2][3] The characteristic structural features are a non-enveloped head and non-contractile tail.
[2] Members of this family are also characterized by their filamentous, cross-banded, non-contractile tails, usually with short terminal and subterminal fibers.
Genomes are double stranded and linear, around 50 kb in length,[2] containing about 70 genes.
The virus exits the host cell by lysis, and holin, endolysin, or spanin proteins.
Typical structure of a siphovirus
Electron micrographs of siphovirus from
Cutibacterium acnes
(formerly
Propionibacterium acnes
). Phages were negatively stained and subjected to transmission electron microscopy. The phages have a head of approximately 55 nm in diameter, loaded with genetic material. Their tails have a size of 150 × 10 nm and are flexible and non-contractile. In the lower micrograph, PAD25 is adhering to bacterial cell debris, and two phages have lost their heads. All phages were classified as Siphoviruses based on their morphology.
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