CRISPR-mediated adaptive immune systems in bacteria and archaea

Annu Rev Biochem. 2013;82:237-66. doi: 10.1146/annurev-biochem-072911-172315. Epub 2013 Mar 11.


Effective clearance of an infection requires that the immune system rapidly detects and neutralizes invading parasites while strictly avoiding self-antigens that would result in autoimmunity. The cellular machinery and complex signaling pathways that coordinate an effective immune response have generally been considered properties of the eukaryotic immune system. However, a surprisingly sophisticated adaptive immune system that relies on small RNAs for sequence-specific targeting of foreign nucleic acids was recently discovered in bacteria and archaea. Molecular vaccination in prokaryotes is achieved by integrating short fragments of foreign nucleic acids into a repetitive locus in the host chromosome known as a CRISPR (clustered regularly interspaced short palindromic repeat). Here we review the mechanisms of CRISPR-mediated immunity and discuss the ecological and evolutionary implications of these adaptive defense systems.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Adaptive Immunity / genetics*
  • Archaea / genetics
  • Archaea / immunology*
  • Bacteria / genetics
  • Bacteria / immunology*
  • Inverted Repeat Sequences / genetics*
  • Inverted Repeat Sequences / immunology
  • RNA, Archaeal / genetics*
  • RNA, Archaeal / immunology
  • RNA, Bacterial / genetics*
  • RNA, Bacterial / immunology
  • Signal Transduction / genetics*
  • Signal Transduction / immunology


  • RNA, Archaeal
  • RNA, Bacterial