Characterization of a bacteriocin from Pediococcus acidilactici PC and comparison of bacteriocin-producing strains using molecular typing procedures

Summary Sixteen pediococcal strains, including eleven Pediococcus acidilactici and five P. pentosaceus strains were screened for inhibitory potential using a deferred overlay spot method against a limited collection of foodborne pathogens. Of those screened, P. acidilactici PC, an organism isolated from fermented sausage, was effective and subsequently screened for inhibitory potential against 46 foodborne pathogens and 28 other lactic acid bacteria. Strain PC produced an antimicrobial agent capable of inhibiting members of the genera Listeria, Clostridium, Leuconostoc and Pediococcus. Gram-negative microorganisms from seven genera, Lactococcus, Streptococcus and Lactobacillus strains were unaffected by the inhibitory substance. The inhibitory agent was sensitive to proteolytic enzymes and exhibited a bactericidal mode of action, confirming the identity as a bacteriocin. In addition, the partially purified bacteriocin was thermally stable up to 100°C for 60 min and maintained inhibitory potential over a wide range of pH values. Plasmid curing studies suggested linkage of bacteriocin production to a 5.5-MDa plasmid. Plasmid profiles were identical for P. acidilactici PC, PAC1.0 and PO2. Genetic analysis of total genomic DNA via DNA fingerprinting and ribosomal RNA (rRNA) typing provided further evidence that these strains were identical. DNA fingerprinting and rRNA typing also showed utility in discrimination between and within other species of pediococci.Published as paper no. 19574 of the contribution series of the Minnesota Agricultural Experiment Station Correspondence to: S. Harlander