PHEROMONE-INDUCED PRODUCTION OF ANTIMICROBIAL PEPTIDES IN LACTOBACILLUS

Production of the bacteriocin sakacin P by Lactobacillus sake LTH673 i s dependent on a secreted 19-residue peptide pheromone (IP-673). The g ene encoding IP-673 (sppIP) was identified and sequenced. SppIP was sh own to be co-transcribed with genes encoding a histidine kinase (sppK) and a response regulator (sppR) typical for signal transduction in ba cteria. Further sequencing and transcription studies have shown that I P-673 induces transcription of its own gene and of what are often cons idered to be all genes necessary for bacteriocin production and immuni ty. Studies with a reporter gene showed that the promoter in front of the sakacin P structural gene (sppA) is strictly regulated. The promot er in front of sppIP turned out to be less strictly regulated, and low basal promoter activity could be detected in uninduced cells. Bacteri ocin production in Bac(-) isolates of L. plantarum C11 could be induce d by the non-cognate IP-673 only after the introduction of sppK, indic ating that sppK encodes the pheromone receptor. These results show tha t bacteriocin production in lactobacilli is regulated using a short, s train-specific peptide pheromone. Growth conditions were shown to have considerable effects on the functionality of this regulatory mechanis m.