UTILIZATION OF THE LEUCOCIN-A EXPORT SYSTEM IN LEUCONOSTOC-GELIDUM FOR PRODUCTION OF A LACTOBACILLUS BACTERIOCIN

The lactacin F complex, composed of LafA and LafX peptides, is produce d by Lactobacillus johnsonii VPI 11088 (ATCC 11506) and is active agai nst various lactobacilli and Enterococcus faecalis. The genetic determ inants encoding the lactacin F peptides, LafA and LafX, are organized in a chromosomal operon comprised of genes lafA, lafX, and ORFZ. The l actacin F operon was introduced into Leuconostoc (Lc.) gelidum UAL187- 22 which produces leucocin A. Leucocin A, a plasmid-encoded bacterioci n, inhibits E. faecalis, Listeria monocytogenes, and other lactic acid bacteria. The culture supernatant of the Leuconostoc transformant con taining the lactacin F operon inhibited both lactacin F-and leucocin A -sensitive indicators. Concurrent expression of both bacteriocins did not alter the production of native leucocin A. Additive inhibitory eff ects due to the presence of both bacteriocins were not observed. An is ogenic derivative of UAL187-22, which has lost the leucocin-encoding p lasmid, was unable to produce active lactacin F when transformed with the appropriate recombinant plasmid. The ability of Lc. gelidum UAL187 -22 to produce lactacin F demonstrates that the export system for leuc ocin A is capable of producing both bacteriocins simultaneously.