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ABSTRACT A widespread system used by bacteria for protection against potentially dangerous foreign DNA molecules consists of the clustered regularly interspaced short palindromic repeats

(CRISPR) coupled with _cas_ (CRISPR-associated) genes1. Similar to RNA interference in eukaryotes2, these CRISPR/Cas systems use small RNAs for sequence-specific detection and neutralization

of invading genomes3. Here we describe the first examples of genes that mediate the inhibition of a CRISPR/Cas system. Five distinct ‘anti-CRISPR’ genes were found in the genomes of

bacteriophages infecting _Pseudomonas aeruginosa_. Mutation of the anti-CRISPR gene of a phage rendered it unable to infect bacteria with a functional CRISPR/Cas system, and the addition of

the same gene to the genome of a CRISPR/Cas-targeted phage allowed it to evade the CRISPR/Cas system. Phage-encoded anti-CRISPR genes may represent a widespread mechanism for phages to

overcome the highly prevalent CRISPR/Cas systems. The existence of anti-CRISPR genes presents new avenues for the elucidation of CRISPR/Cas functional mechanisms and provides new insight

into the co-evolution of phages and bacteria. Access through your institution Buy or subscribe This is a preview of subscription content, access via your institution ACCESS OPTIONS Access

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subscriptions * Read our FAQs * Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS BACTERIOPHAGES SUPPRESS CRISPR–CAS IMMUNITY USING RNA-BASED ANTI-CRISPRS Article Open access

18 October 2023 DIVERSE VIRAL CAS GENES ANTAGONIZE CRISPR IMMUNITY Article 04 September 2024 PROPHAGE INTEGRATION INTO CRISPR LOCI ENABLES EVASION OF ANTIVIRAL IMMUNITY IN _STREPTOCOCCUS

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7422–7426 (2008) Article  CAS  Google Scholar  Download references ACKNOWLEDGEMENTS We thank D. Guttman, Y.-H. Cho, K. Cady and G. O’Toole for providing _P. aeruginosa_ strains and phages.

We also thank K. Severinov for providing the M13 phage and _E. coli_ strains required for assaying the type 1-E system. We thank J. Brumell, A. Spence and W. Navarre for reading the

manuscript. We also thank D. Bona for technical assistance. This work was supported by an Operating Grant to K.L.M. (fund number MOP- 6279) and an Emerging Team Grant to A.R.D. and K.L.M.

(fund number XNE86943), both of which were from the Canadian Institutes for Health Research. J.B.D. was supported by a CIHR Canada Graduate Scholarship Doctoral Award. AUTHOR INFORMATION

AUTHORS AND AFFILIATIONS * Department of Molecular Genetics, University of Toronto, Toronto, M5S 1A8, Ontario, Canada Joe Bondy-Denomy & Alan R. Davidson * Department of Biochemistry,

University of Toronto, Toronto, M5S 1A8, Ontario, Canada April Pawluk & Alan R. Davidson * Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, M5S

3E1, Ontario, Canada Karen L. Maxwell Authors * Joe Bondy-Denomy View author publications You can also search for this author inPubMed Google Scholar * April Pawluk View author publications

You can also search for this author inPubMed Google Scholar * Karen L. Maxwell View author publications You can also search for this author inPubMed Google Scholar * Alan R. Davidson View

author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS J.B.-D. designed experiments, performed experiments and wrote the manuscript, A.P. performed

experiments, K.L.M. supervised experiments, and A.R.D. designed experiments and wrote the manuscript. CORRESPONDING AUTHOR Correspondence to Alan R. Davidson. ETHICS DECLARATIONS COMPETING

INTERESTS The authors have filed a provisional patent pertaining to biotechnological applications of anti-CRISPR genes. SUPPLEMENTARY INFORMATION SUPPLEMENTARY INFORMATION This file contains

Supplementary Figures 1-12, Supplementary Tables 1-2 and a Supplementary Reference. (PDF 3310 kb) SUPPLEMENTARY DATA This file contains Supplementary Table 3 with A, Bacteria and Phage

strain information, B, Primers used in this study and C, Plasmids which were constructed. (XLSX 19 kb) POWERPOINT SLIDES POWERPOINT SLIDE FOR FIG. 1 POWERPOINT SLIDE FOR FIG. 2 RIGHTS AND

PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Bondy-Denomy, J., Pawluk, A., Maxwell, K. _et al._ Bacteriophage genes that inactivate the CRISPR/Cas bacterial

immune system. _Nature_ 493, 429–432 (2013). https://doi.org/10.1038/nature11723 Download citation * Received: 06 August 2012 * Accepted: 26 October 2012 * Published: 16 December 2012 *

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