Discovery and Characterization of Cas9 Inhibitors Disseminated across Seven Bacterial Phyla

？ A genetic circuit designed to functionally select anti-CRISPR genes from metagenomes ？ Four protein families, AcrIIA7–10, that inhibit Cas9 in vivo and in vitro were identified ？ AcrIIA7–10 are widely distributed across seven bacterial phyla ？ Dissemination patterns of AcrIIA7–10 suggest interphylum horizontal gene transfe