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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Dairy and Functional Foods Research » Research » Publications at this Location » Publication #297790
Title: BlpU is a broad-spectrum bacteriocin in Streptococcus thermophilus

Author
item Renye, John
item SOMKUTI, GEORGE - Retired ARS Employee
item Qi, Phoebe
item STEINBERG, DENNIS - Retired ARS Employee
item McAnulty, Michael
item Miller, Amanda
item Guron, Giselle
item Oest, Adam

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2024
Publication Date: 7/16/2024
Citation: Renye Jr, J.A., Somkuti, G.A., Qi, P.X., Steinberg, D.H., Mcanulty, M.J., Miller, A.L., Guron, G.P., Oest, A.M. 2024. BlpU is a broad-spectrum bacteriocin in Streptococcus thermophilus. Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2024.1409359.
DOI: https://doi.org/10.3389/fmicb.2024.1409359

Interpretive Summary: The dairy industry is continually looking to improve the quality and safety of fermented foods while attempting to cut the costs of these products. Lactic acid bacteria are required for production of these foods and offer a potential solution, as some have been shown to inhibit the growth of other bacteria. Streptococcus thermophilus is a dairy culture used in the production of yogurt and cheeses, and some strains of this bacterium have been shown to produce natural preservatives that can protect dairy products against spoilage and pathogenic bacteria. Natural preservative production is controlled by specific genes, which are not present in all cultures. Using special detection techniques, ARS scientists have studied the genetic components of this complex production system in yogurt starter cultures that display antimicrobial activity. The genes required for antimicrobial activity were identified and their production was measured within the yogurt cultures. It was determined that one specific gene was especially active in a specific Streptococcus thermophilus strain, which may explain its ability to produce a natural preservative during the yogurt fermentation process. The intended goal of this work is to develop methods for increasing the production of these preservatives in Streptococcus thermophilus cultures, so that fermented dairy products (cheeses, yogurt) may be safe and protected against pathogenic microorganisms.

Technical Abstract: Streptococcus thermophilus strain B59671 naturally produces thermophilin 110, a broad-spectrum bacteriocin encoded within the bacteriocin-like peptide (blp) gene cluster, and thermophilin 13 from a separate chromosomal locus. Analysis of the blp gene cluster revealed two genes, blpU and blpK, as potentially encoding bacteriocins. Deletion of blpK from the B59671 chromosome did not result in a loss of antimicrobial activity against either S. thermophilus ST113 or Pediococcus acidilactici F. A deletion mutant of blpU could not be generated in B59671, but the mature BlpU peptide obtained through overexpression in E. coli BL21 or chemical synthesis inhibited the growth of S. thermophilus strains, Streptococcus mutans UA159, P. acidilactici F, and Listeria innocua GV9 L-S, evidencing as a broad-spectrum bacteriocin that does not require modification for activity. This study also showed that the transcription of blpU was approximately 16-fold higher in B59671 than in an induced culture of S. thermophilus LMD-9, which produces a blp-encoded bacteriocin. The increased expression of BlpU in B59671 may explain the unique antimicrobial spectrum associated with this strain. Additionally, it was shown that a blpC deletion mutant of B59671, which prevents expression of BlpU and BlpK, inhibited the growth of other S. thermophilus strains and Bacillus cereus, suggesting that thermophilin 13 produced by B59671 possessed both intra- and interspecies antimicrobial activity. While this study confirmed that BlpU can function as an independent antimicrobial peptide, further studies are required to determine if BlpK can function independently as a broad-spectrum antimicrobial.