Fig. 2.

Use of CRISPR–Cas9 systems for genome editing. a Schematic strategies of gene insertion using RecT-assisted CRISRP–Cas9 system. b Schematic strategies of gene deletion using RecT-assisted CRISRP–Cas9 system. Plasmid pTHCas9 harboring the Cas9 nuclease, tracrRNA and crRNA and the donor ssDNA substrates were electroporated into Lc. lactis cells expressing RecT. After ssDNA recombineering, the positive mutants were counter selected by CRISPR–Cas9. DR direct repeats