Proceedings of the National Academy of Sciences, Volume 123, Issue 24, June 2026. SignificanceA census of Acrs withinEnterobacteriaceaereveals that the most widespread anti-CRISPR cluster in this order consists ofacrIE9,acrIE10, andacrIE13protein, identified in this study. Mechanistically, AcrIE9 binds to the Cas7 subunit of the β¦