Single-Nucleotide Microbial Genome Editing Using CRISPR-Cas12a.

Microbial genome editing can be achieved by donor DNA-directed mutagenesis and CRISPR-Cas12a-mediated negative selection. Single-nucleotide-level genome editing enables the manipulation of microbial cells exactly as designed. Here, we describe single-nucleotide substitutions/indels in the target DNA of E. coli genome using a mutagenic DNA oligonucleotide donor and truncated crRNA/Cas12a system. The maximal truncation of nucleotides at the 3'-end of the crRNA enables Cas12a-mediated single-nucleotide-level precise editing at galK targets in the genome of E. coli.