pCasSA plasmid. (A) Plasmid map of the Staphylococcus aureus CRISPR–Cas9 genome-editing plasmid pCasSA, with relevant features indicated. (B) DNA sequence showing the synthetic guide RNA (sgRNA) sequence with a spacer insertion site flanked by BsaI restriction sites and XbaI and XhoI sites for inserting the DNA repair template. (Reprinted, with permission, from Chen et al. 2017, © American Chemical Society.)