INDUCTION OF BACTERIOCIN IN CARNOBACTERIUM-PISCICOLA LV17

Domination of Carnobacterium divergens LV13 by a bacteriocin-producing (bac(+)) organism Carnobacterium piscicola LV17 was dependent on the level of inoculum of the producer strain and its bacteriocin production. When C. piscicola LV17 was grown in APT broth from an initial inoculum of less than or equal to 10(4) cfu ml(-1), bacteriocin was not produced (bac(-)) although maximum population was reached. The culture remained bac(-) during subsequent inoculation at 10(2)-10(7) cfu ml(-1) unless it was first grown on solid medium or if heat-treated supernatant fluids from a bac(+) culture of C, piscicola LV17, LV17A or LV17B were added to the culture prior to the stationary phase of growth. Use of purified carnobacteriocins from C. piscicola LV17A and LV17B confirmed their role in regulation of the bac(+) phenotype. The need for induction might account in part for differences in bacteriocin production by cultures in liquid and on solid growth media.