Development of a genetically engineered Escherichia coli strain for plasmid transformation in Corynebacterium glutamicum

•A novel strain E. coli AU1 was developed by chromosomally integrating the methyltransferase gene cglIM from C. glutamicum.•The plasmid isolated from E. coli AU1 is able to resist the cglIR-cglIIR restriction system in C. glutamicum.•E. coli AU1 is a useful intermediate host for efficient transformation of C. glutamicum.

Gene disruption and replacement in Corynebacterium glutamicum is dependent upon a high transformation efficiency. The cglIR-cgIIR restriction system is a major barrier to introduction of foreign DNA into Corynebacterium glutamicum cells. To improve the transformation efficiency of C. glutamicum, the cglIM gene encoding methyltransferase in the cglIR-cglIIR-cglIM restriction-modification system of C. glutamicum ATCC 13032 was chromosomally integrated and expressed in Escherichia coli, resulting in an engineered strain E. coli AU1. The electro-transformation experiments of C. glutamicum ATCC 13032 with the E. coli-C. glutamicum shuttle plasmid pAU4 showed that the transformation efficiency of C. glutamicum with pAU4 DNA extracted from E. coli TG1/pAU4 was 1.80 ± 0.21 × 102 cfu/μg plasmid DNA, while using pAU4 DNA extracted from E. coli AU1/pAU4, the transformation efficiency reached up to 5.22 ± 0.33 × 106 cfu/μg plasmid DNA. The results demonstrated that E. coli AU1 is able to confer the cglIM-specific DNA methylation pattern to its resident plasmid, which makes the plasmid resistant to the cglIR-cglIIR restriction and efficiently transferred into C. glutamicum. E. coli AU1 is a useful intermediate host for efficient transformation of C. glutamicum.