Phage

A phage (also called bacteriophage) (in Greek phageton = food/consumption) is a small virus that infects only bacteria. Like viruses that infect eukaryotes, phages consist of an outer protein hull and the enclosed genetic material (which consists of double-stranded DNA in 95% of the phages known) of 5 to 650 kbp (kilo base pairs) with a length of 24 to 200 nm. The vast majority of phages (95%) have a tail to let them inject their genetic material into the host. Phages were discovered independently by Frederick Twort in 1915 and by Félix d’Herelle in 1917. d'Herelle continued his research and development in the Soviet Union.

Model bacteriophages

Following is a list of bacteriophages that are extensively studied:

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• λ phage - Lysogen
• T4 phage (169 to 170 kbp, 200 nm long)
• T7 phage
• R17 phage
• M13 phage
• MS2 phage (23-25 nm in size)
• G4 phage
• P1 phage
• P2 phage
• N4 phage
• ?6 phage