FIG 1.

General scheme of using endogenous CRISPR-Cas systems for genome editing in bacteria and archaea. (A) The crRNA is expressed from a vector-borne CRISPR miniarray under the control of native or inducible promoters. The crRNA forms a ribonucleoprotein (crRNP) complex with endogenous Cas proteins, which recognizes and directs the cleavage of the PAM-associated protospacer, localized at the target chromosome region. This leads to chromosome disruption and cell death. (B) An editing plasmid, additionally carrying homologous arms (the left arm [LA] and the right arm [RA]), allows recombination between the plasmid and the chromosome to occur before CRISPR interference. The crRNP targets the PAM-protospacer on the plasmid, which leads to the elimination of the plasmid and preservation of the chromosomal mutants.