An updated evolutionary classification of CRISPR-Cas systems

Kira S. Makarova, Yuri I. Wolf, Omer S. Alkhnbashi, Fabrizio Costa, Shiraz A. Shah, Sita J. Saunders, Rodolphe Barrangou, Stan J.J. Brouns, Emmanuelle Charpentier, Daniel H. Haft, Philippe Horvath, Sylvain Moineau, Francisco J.M. Mojica, Rebecca M. Terns, Michael P. Terns, Malcolm F. White, Alexander F. Yakunin, Roger A. Garrett, John Van Der Oost, Rolf BackofenEugene V. Koonin

Research output: Contribution to journalArticlepeer-review

1806 Scopus citations


The evolution of CRISPR-cas loci, which encode adaptive immune systems in archaea and bacteria, involves rapid changes, in particular numerous rearrangements of the locus architecture and horizontal transfer of complete loci or individual modules. These dynamics complicate straightforward phylogenetic classification, but here we present an approach combining the analysis of signature protein families and features of the architecture of cas loci that unambiguously partitions most CRISPR-cas loci into distinct classes, types and subtypes. The new classification retains the overall structure of the previous version but is expanded to now encompass two classes, five types and 16 subtypes. The relative stability of the classification suggests that the most prevalent variants of CRISPR-Cas systems are already known. However, the existence of rare, currently unclassifiable variants implies that additional types and subtypes remain to be characterized.

Original languageEnglish (US)
Pages (from-to)722-736
Number of pages15
JournalNature Reviews Microbiology
Issue number11
StatePublished - Nov 1 2015

All Science Journal Classification (ASJC) codes

  • Microbiology
  • General Immunology and Microbiology
  • Infectious Diseases


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