Development of a CRISPR/Cas9 Nickase (nCas9)-Mediated Genome Editing Tool in .

Streptomycetes have a strong ability to produce a vast array of bioactive natural products (NPs) widely used in agriculture and veterinary/human medicine. The recently developed CRISPR/Cas9-based genome editing tools have greatly facilitated strain improvement for target NP overproduction as well as novel NP discovery in . However, CRISPR/Cas9 shows high toxicity to the host, limiting its application in many strains with a low DNA transformation efficiency.