Efficient electrotransformation of Corynebacterium diphtheriae with a mini-replicon derived from the Corynebacterium glutamicum plasmid pGA1

Efficient transformation of the human pathogen Corynebacterium diphtheriae was achieved with novel cloning vectors consisting of a mini-replicon from the cryptic C. glutamicum plasmid pGA1 as well as of the aph(3')-IIa or tetA(Z) antibiotic resistance genes. Plasmid-containing transformants of C. diphtheriae were recovered at frequencies ranging from 1.3 x 10(5) to 4.8 x 10(6) colony forming units (cfu)/mug of plasmid DNA. Vector DNA was directly transferred from Escherichia coli into C. diphtheriae with frequencies up to 5.6 x 10(5) cfu/mug of plasmid DNA. On the basis of the pGA1 mini-replicon, an expression vector system was established for C. diphtheriae by means of the P-tac promoter and the green fluorescent reporter protein. In addition, other commonly used vector systems from C. glutamicum, including the pBL1 and pHM1519 replicons, and the sacB conditionally lethal selection market from Bacillus subtilis, were shown to be functional in C. diphtheriae. Thus, the ability to apply the standard methods of C. glutamicum recombinant DNA technology will greatly facilitate the functional analysis of the recently completed C. diphtheriae genome sequence.