Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 1999
Publication Date: N/A
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Interpretive Summary: The dairy fermentation culture Streptococcus thermophilus enjoys food-grade status since it is ingested together with the food product. The culture is an ideal host for new genes of natural antimicrobial substances such as pediocin, a peptide with inhibitory activity against several foodborne pathogens, including Listeria. By using genetic engineering techniques, several special DNA molecules were constructed for producing the pediocin gene complex in intermediary hosts such as Escherichia coli in larger quantities needed for uptake by selected dairy fermentation cultures. The pediocin gene remained functional in dairy streptococci and lactococci for several generations and the antimicrobial peptide produced inhibited the growth of the foodborne pathogen Listeria. The stable maintenance of the pediocin gene in lactic cultures will allow the development of fermented dairy foods with a built-in bioprotective shield to prevent contamination by Listeria.
Technical Abstract: Production of pediocin in Pediococcus acidilactici is associated with pMBR1.0, which encodes prepediocin, a pediocin immunity protein, and two proteins involved in secretion and precursor processing. These four genes are organized as an operon under control of a single promoter. We have constructed shuttle vectors that contain all four structural genes, the chromosomal promoter STp2201 from Streptococcus thermophilus, and repA fro the 2-kbp S. thermophilus plasmid pER8. The recombinant plasmid, pPC318, expressed and secreted active pediocin in Escherichia coli. S. thermophilus Lactococcus lactis subsp. lactis, and Enterococcus faecalis were electro- transformed with pPC418, a modified vector fitted with an erythromycin resistance tracking gene. Pediocin was produced and secreted in each of the lactic acid bacteria and production was stable for up to ten passages. The expression of pediocin in dairy fermentation microbes has important implications for bacteriocins as food preservatives in dairy products.