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Updated: May 16, 2026

Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins
Published on: September 30, 2014
BlpC-regulated bacteriocin production in Streptococcus thermophilus
John A Renye1, George A Somkuti
1United States Department of Agriculture, Eastern Regional Research Center, Agricultural Research Service, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA. john.renye@ars.usda.gov
Abstract:
Streptococcus thermophilus B59671 produces a bacteriocin with anti-pediococcal activity, but genes required for its production are not characterized. Genome sequencing of S. thermophilus has identified a genetic locus encoding a quorum sensing (QS) system that regulates production of class II bacteriocins. However, in strains possessing this gene cluster, production of bacteriocin like peptides (Blp) was only observed when excess pheromone was provided. PCR analysis revealed this strain possessed blpC, which encodes the 30-mer QS pheromone. To investigate if BlpC regulates bacteriocin production in S. thermophilus B59671, an integrative vector was used to replace blpC with a gene encoding for kanamycin resistance and the resulting mutant did not inhibit the growth of Pediococcus acidilactici. Constitutive expression of blpC from a shuttle vector restored the bacteriocin production, confirming the blp gene cluster is essential for bacteriocin activity in S. thermophilus B59671.
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