The repetitive DNA elements called CRISPRs and their associated genes: evidence of horizontal transfer among prokaryotes

J Mol Evol. 2006 Jun;62(6):718-29. doi: 10.1007/s00239-005-0223-z. Epub 2006 Apr 11.


We have found direct DNA repeats 21-47 bp in length interspersed with nonrepetitive sequences of similar length, or clustered regularly interspaced short palindromic repeats (CRISPRs) in a wide range of diverse prokaryotes, including many Archaeal and Eubacterial species. A number of cas, CRISPR-associated genes have also been characterized in many of the same organisms. Phylogenetic analysis of these cas genes suggests that the CRISPR loci have been propagated via HGT, horizontal gene transfer. We suggest a mechanism by which this HGT has occurred, namely, that the CRISPR loci can be carried between cells on megaplasmids > or = 40 kb in length.

MeSH terms

  • Base Sequence
  • Desulfovibrio / genetics
  • Gene Transfer, Horizontal*
  • Genes, Bacterial*
  • Models, Genetic*
  • Molecular Sequence Data
  • Phylogeny
  • Prokaryotic Cells*
  • Repetitive Sequences, Nucleic Acid / genetics*
  • Sequence Alignment
  • Shewanella / genetics