Studies on maintenance of vector pBK2 in Corynebacterium acetoacidophilum by co-culture experiments in a continuous bioreactor

Characterization of a novel plasmid pXZ608 from Corynebacterium glutamicum

The complete nucleotide sequence of a novel cryptic plasmid pXZ608 from Corynebacterium glutamicum 227 was determined. pXZ608 was 5949 bp with six open reading frames (ORF1-6). The predicted ORF1 gene product was homologous to replication proteins of rolling circle replication plasmids. The conserved single- and double-stranded origins of rolling circle replication were found, and interestingly, the two origins were both located on ORF1, which indicated that the Rep protein encoded by ORF1 could bind to its own gene region. Deletion analysis revealed that the minimal replicon was located on the 2.14-kb SacI-BstEII fragment.

Construction of fusion vectors of corynebacteria: expression of glutathione-S-transferase fusion protein in Corynebacterium acetoacidophilum ATCC 21476

A series of fusion vectors containing glutathione-S-transferase (GST) were constructed by inserting GST fusion cassette of Escherichia coli vectors pGEX4T-1, -2 and -3 in corynebacterial vector pBK2. Efficient expression of GST driven by inducible tac promoter of E. coli was observed in Corynebacterium acetoacidophilum. Fusion of enhanced green fluorescent protein (EGFP) and streptokinase genes in this vector resulted in the synthesis of both the fusion proteins. The ability of this recombinant organism to produce several-fold more of the product in the extracellular medium than in the intracellular space would make this system quite attractive as far as the downstream processing of the product is concerned.

Plasmids of corynebacteria

Corynebacteria are pleomorphic, asporogenous, Gram-positive bacteria. Included in this group are nonpathogenic soil corynebacteria, which are widely used for the industrial production of amino acids and detergents, and in biotransformation of steroids. Other members of this group are plant and animal pathogens. This review summarizes the current information available about the plasmids of corynebacteria. The emphasis is mainly on the small plasmids, which have been used for construction of vectors for expression of genes in these bacteria. Moreover, considerable information is now available on their nucleotide sequence, gene organization and modes of replication, which would make it possible to further manipulate these plasmids. Other plasmid properties, such as incompatibility and host range, are also discussed. Finally, use of these plasmids as cloning vectors for the expression of heterologous proteins using corynebacteria as hosts is also summarized to highlight the potential of these bacteria as hosts for recombinant DNA.