Classification
The dsDNA tailed phages, or Caudovirales, account for 95% of all the phages reported in the scientific literature, and possibly make up the majority of phages on the planet. However, other phages occur abundantly in the biosphere, with different virions, genomes and lifestyles. Phages are classified by the International Committee on Taxonomy of Viruses (ICTV) according to morphology and nucleic acid.
Nineteen families are currently recognised that infect bacteria and archaea. Of these, only two families have RNA genomes and only five families are enveloped. Of the viral families with DNA genomes, only two have single-stranded genomes. Eight of the viral families with DNA genomes have circular genomes, while nine have linear genomes. Nine families infect bacteria only, nine infect archaea only, and one (Tectiviridae) infects both bacteria and archaea.
| Order | Family | Morphology | Nucleic acid | Examples |
|---|---|---|---|---|
| Caudovirales | Myoviridae | Nonenveloped, contractile tail | Linear dsDNA | T4 phage |
| Siphoviridae | Nonenveloped, noncontractile tail (long) | Linear dsDNA | λ phage, Bacteriophage T5 | |
| Podoviridae | Nonenveloped, noncontractile tail (short) | Linear dsDNA | T7 phage | |
| Ligamenvirales | Lipothrixviridae | Enveloped, rod-shaped | Linear dsDNA | Acidianus filamentous virus 1 |
| Rudiviridae | Nonenveloped, rod-shaped | Linear dsDNA | Sulfolobus islandicus rod-shaped virus 1 | |
| Unassigned | Ampullaviridae | Enveloped, bottle-shaped | Linear dsDNA | |
| Bicaudaviridae | Nonenveloped, lemon-shaped | Circular dsDNA | ||
| Clavaviridae | Nonenveloped, rod-shaped | Circular dsDNA | ||
| Corticoviridae | Nonenveloped, isometric | Circular dsDNA | ||
| Cystoviridae | Enveloped, spherical | Segmented dsRNA | ||
| Fuselloviridae | Nonenveloped, lemon-shaped | Circular dsDNA | ||
| Globuloviridae | Enveloped, isometric | Linear dsDNA | ||
| Guttavirus | Nonenveloped, ovoid | Circular dsDNA | ||
| Inoviridae | Nonenveloped, filamentous | Circular ssDNA | ||
| Leviviridae | Nonenveloped, isometric | Linear ssRNA | MS2, Qβ | |
| Microviridae | Nonenveloped, isometric | Circular ssDNA | ΦX174 | |
| Plasmaviridae | Enveloped, pleomorphic | Circular dsDNA | ||
| Tectiviridae | Nonenveloped, isometric | Linear dsDNA |
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