Functional analysis of promoters involved in quorum sensing-based regulation of bacteriocin production in Lactobacillus

Bacteriocin production in Lactobacillus sake LTH673 involves at least four operons: a regulatory operon (spplPKR); two operons encoding bacteriocins a nd their immunity proteins (sppAiA and orfX); and an operon needed for secr etion (sppTE). We show here that the response regulator encoded by sppR in L. sake LTH673, as well as the homologous response regulators encoded by pl nC and plnD in Lactobacillus plantarum C11, bind to characteristic repeats found in the -80 to -40 regions of spp operons, The promoters controlling b acteriocin operons are strictly regulated, and their activity is increased more than 1000-fold upon activation. Constitutive expression for the regula tory and transport operons is driven, at least in part, by promoters upstre am of the -80 to -40 regions. Peak promoter activity of the regulatory and transporter operons precedes that of the two bacteriocin operons. The resul ts reveal how promoters involved in quorum sensing-based regulation of bact eriocin production in Lactobacillus differ in strength, leakiness and timin g of their activity.