Production of Plantaricin NC 8 by Lactobacillus 1 plantarum NC 8 is Induced in the Presence of 2 Different Types of Gram - positive Bacteria

1 2 Lactobacillus plantarum NC8 was shown to produce plantaricin NC8 (PLNC8), a recently 3 purified and genetically characterized inducible class IIb bacteriocin, only when it was co4 cultured with other Gram-positive bacteria. Among 82 strains belonging to the genera 5 Bacillus, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Listeria, Pediococcus, 6 Staphylococcus and Streptococcus, forty-one of them where shown to induce PLNC8 7 production in L. plantarum NC8. There was apparently no relationship between sensitivity 8 of strains and their ability to induce the bacteriocin thus indicating that both the inducer 9 and sensitive phenotypes may not be linked. In some instances, the induction was 10 promoted by both living and heat-killed cells of the inducing bacteria. However, no 11 PLNC8-inducing activity was found in their respective cell-free, pure culture supernatants. 12 Inducer strains promoted also production of a PLNC8-autoinducing activity by L. 13 plantarum NC8, which was found only in the cell-free co-culture supernatants showing 14 inhibitory activity. This PLNC8-autoinducing activity was shown to be diffusible, heat 15 resistant and of proteinaceous nature, being different from the bacteriocin itself. Our results 16 suggest that the presence of specific Gram-positive bacteria act as an environmental 17 stimulus activates PLNC8 production by L. plantarum NC8 as well as a PLNC818 autoinducing activity which triggers or maintains bacteriocin production in the absence of 19 inducing cells. 20 21 22 23