Transformation of Corynebacterium diphtheriae, Corynebacterium ulcerans, Corynebacterium glutamicum, and Escherichia coli with the C. diphtheriae plasmid pNG2.

The transfection and transformation of members of two species of pathogenic corynebacteria, Corynebacterium diphtheriae and Corynebacterium ulcerans, is described. Protoplasts were produced by treatment with lysozyme following growth in glycine, and a medium was defined on which a significant fraction of the osmotically sensitive cells were regenerated. Transfections were carried out with DNA from corynephage 782, a member of the beta family of converting phages, and transformations were performed with DNA of plasmid pNG2, a 9500-kDa plasmid that was isolated from an erythromycin-resistant strain of C. diphtheriae and carries the resistance gene. Strains of Corynebacterium glutamicum and Escherichia coli were also successfully transformed with pNG2 DNA. Transfection frequencies were in the range of 3-8 X 10(3) plaque-forming units/micrograms of phage DNA, and transformation frequencies were in the range of 0.2-150 colony-forming units/micrograms of plasmid DNA. Plasmid pNG2 replicated and was stably maintained in all transformants both in the presence or absence of erythromycin. Thus, it displayed the ability to replicate in strains of both Gram-positive and Gram-negative bacteria without the intervention of genetic engineering. pNG2 DNA isolated from any of the transformed strains was able to transform all parental strains. The host range of pNG2 suggests its possible utility in or as a shuttle vector for the study and manipulation of genes from corynebacterial strains of animal origin.