The Phage


Are Bacteriophages (Phages) DNA Or RNA Viruses?

DNA and RNA. Credit Gabriela Slizewska

A bacteriophage, also known as a phage, is a virus that infects and replicates within bacteria and archaea. Like any other viruses, they are made up of nucleic acids encased in a protein coat (capsid). Although morphological appearance is one of the characteristics used to classify phages (Phage morphologies), evolving molecular technologies have enabled other cellular characteristics to be incorporated into microbe classification. One of the molecular-level aspects is the virus’s genomic content. Phage genomic composition is extremely diverse, consisting of DNA or RNA, which can be single-stranded (ss) or double-stranded (ds). The genomes of RNA viruses are smaller than those of their counterparts (DNA viruses). Many scientists have largely ignored RNA viruses in their research, preferring to concentrate on DNA viruses. Until now, only two families of these viruses have been identified as having RNA as their genomes. RNA phages are frequently used as prototypes in modern recombinant virus-like particle (VLP) technologies. 

DNA phage families

The International Committee for the Taxonomy of Viruses (ICTV) currently divides DNA bacteriophages into eight distinct families (For current taxonomy visit the ICTV website). Few are single-stranded DNA (ssDNA) bacteriophage species, while the majority are double-stranded DNA (dsDNA) bacteriophage species. These species are derived from a wide range of host bacteria.

List of bacteriophages with DNA genomes

  • T4-Infect E. coli
  • Enterobacteria phage T2
  • Enterobacteria phage T6
  • lambda
  • Mu
  • M13

RNA phage families

Only two RNA bacteriophage families are recognized: the single-stranded RNA (ssRNA) bacteriophage family Leviviridae, which includes recognized species such as Enterobacteria phage Q, Enterobacteria phage F1, Enterobacteria phage MS2, and Enterobacteria phage GA, and the segmented, double-stranded RNA (dsRNA) family Cystoviridae that contains only one known species (Pseudomonas phage ϕ6).

List of bacteriophages with RNA genomes

  • MS2-Infect E. coli and some other members of Enterobacteriaceae
  • Bacteriophage f2-Infect E. coli
  • Bacteriophage Qβ (Q beta)-infects bacteria that have F-pili
  • Pseudomonas phage ϕ6
  • Enterobacteria phage GA



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