a, Strain PAO1 was engineered to express the type I-C Cas genes and distinct crRNAs that target the indicated phages. b, Strain PAO1 was engineered to express the type II-A Cas9 protein and distinct sgRNAs that target the indicated phages. c, The endogenous type I R-M system (hsdRSM) in wild-type PAO1 and a mutant strain with an isogenic hsdR knockout (PAO1∆ hsdR) was assayed using phages that were propagated on PAO1 or PAK as indicated, and strains were subjected to a plaque assay. All plaque assays were conducted as in Fig. 1a and were replicated twice with similar results.