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Quorum-Sensing Regulation of the Production of Blp Bacteriocins in Streptococcus thermophilus ^,

Unité de Génétique, Institut des Sciences de la Vie, Université catholique de Louvain, Place Croix du Sud 5, B-1348 Louvain-la-Neuve, Belgium,¹ Institut National de la Recherche Agronomique, Unité de Génétique Microbienne,² Unité de Biochimie Bactérienne, Domaine de Vilvert, 78350 Jouy-en-Josas, France,³ Laboratoire de Microbiologie et de Biochimie Appliquées, UMR 5248 CBMN, CNRS-Université de Bordeaux 1-ENITAB, F-33170 Gradignan, France⁴

Received 19 June 2007/ Accepted 13 July 2007

The blp gene cluster identified in the genome sequences of Streptococcus thermophilus (blp_St) LMG18311, CNRZ1066, and LMD-9 displays all the characteristics of a class II bacteriocin locus. In the present study, we showed that the blp_St locus is only fully functional in strain LMD-9 and regulates the production of antimicrobial peptides that inhibit strains LMG18311 and CNRZ1066. The blp_St cluster of LMD-9 contains 23 genes that are transcriptionally organized in six operons: blpABC_St (peptide transporter genes and pheromone gene); blpRH_St (two-component regulatory system genes); blpD_St-orf1, blpU_St-orf3, and blpE-F_St (bacteriocin precursors and immunity genes); and blpG-X_St (unknown function). All the operons, except the regulatory unit blpRH_St, were shown to be coregulated at the transcriptional level by a quorum-sensing mechanism involving the mature S. thermophilus pheromone BlpC* (BlpC*_St), which was extracellularly detected as two active forms (30 and 19 amino acids). These operons are differentially transcribed depending on growth phase and pheromone concentration. They all contain a motif with two imperfect direct repeats in their mapped promoter regions that could serve as binding sites of the response regulator BlpR_St. Through the construction of deletion mutants, the blp_St locus of strain LMD-9 was shown to encode all the essential functions associated with bacteriocin production, quorum-sensing regulation, and immunity.

Published ahead of print on 10 August 2007.

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This article has been cited by other articles:

• Fontaine, L., Hols, P. (2008). The Inhibitory Spectrum of Thermophilin 9 from Streptococcus thermophilus LMD-9 Depends on the Production of Multiple Peptides and the Activity of BlpGSt, a Thiol-Disulfide Oxidase. Appl. Environ. Microbiol. 74: 1102-1110 [Abstract] [Full Text]