Cloning of the Xanthomonas campestris pv glycines 8ra gene for glycinecin A secretion

Glycinecin A is a narrow-spectrum bacteriocin that is produced by Xanthomonas campestris pv glycines 8ra, and which has potential as a control agent for Xanthomonas phytopathogens. Most of the glycinecin A produced by Xanthomonas campestris pv glycines 8ra was found in the culture medium, whereas the recombinant glycinecin A expressed in E. coli was located intracellularly (S. Heu, J. Oh, Y. Kang, S. Ryu, S.K. Cho, Y. Cho & M. Cho. 2001 Applied and Environmental Microbiololgy 67, 4105–4110). The plasmid pBL5, which contains a 6-kb DNA fragment that includes the glyA and glyB genes, secreted glycinecin A into the medium when expressed in E. coli. Serial deletions of pBL5 were performed, to clone the gene (glyC) that was involved in secreting the recombinant glycinecin A from E. coli. The glyC gene was located upstream of glyA and glyB, and encoded a protein of 51 amino acids. Complementation of the glyC mutation restored the secretion of recombinant glycinecin A in E. coli. The glyC gene appears to be critical for recombinant glycinecin A secretion, since deletion of glyC dramatically reduced glycinecin A secretion into the culture medium.