Combining CRISPR-Cpf1 and Recombineering Facilitates Fast and Efficient Genome Editing in Escherichia coli.

Abstract

Clustered regularly interspaced short palindromic repeat (CRISPR)-based gene-editing technology has been widely used in various microorganisms due to its advantages of low cost, high efficiency, easy operation, and multiple functions. In this study, an efficient and fast double-plasmid gene-editing system pEcCpf1/pcrEG was constructed in Escherichia coli based on CRISPR/Cpf1. First, gene knockout and integration efficiency were verified in eight different kinds of protospacer adjacent motif (PAM) regions. Then, the transformation method was optimized, and the efficiency of gene knockout or gene integration of this system increased to nearly 100%, and the large-length fragments could be integrated into the genome in E. coli BL21 (DE3). The system was also optimized by replacing the homologous recombination system in plasmid pEcCpf1, resulting in pEcCpf1H, which could perform precise single-point mutation, terminator insertion, short-sequence insertion, or gene knockout with high efficiency using a 90 nt (nucleotide) single-stranded primer. Further, multiple genes could be edited simultaneously. Next, these two systems were demonstrated in other E. coli strains. Finally, as an application, the system was used to engineer the synthesis pathway of l-histidine in the engineered strain. The titer of l-histidine in a shake flask reached 7.16 g/L, a value increased by 84.1% compared to the starting strain. Thus, this study provided an effective tool for metabolic engineering of E. coli.