ABSTRACTBacteriocins from lactic acid bacteria (LAB) are of increasing interest in recent years due to their potential as natural preservatives against food and beverage spoilage microorganisms. In a screening study for LAB, we isolated from olives a strain,Lactobacillus plantarumNI326, with activity against the beverage-spoilage bacteriumAlicyclobacillus acidoterrestris. Genome sequencing of NI326 enabled the identification of a gene cluster (designatedplc) encoding a putative circular bacteriocin and proteins involved in its modification, transport, and immunity. This novel bacteriocin, named plantaricyclin A (PlcA), was grouped into the circular bacteriocin subgroup II due to its high degree of similarity with other gassericin A-like bacteriocins. Purification of PlcA from the supernatant ofLb. plantarumNI326 resulted in an active peptide with a molecular mass of 5,570 Da, corresponding to that predicted from the (processed) PlcA amino acid sequence. Theplcgene cluster was cloned and expressed inLactococcus lactisNZ9000, resulting in the production of an active 5,570-Da bacteriocin in the supernatant. PlcA is believed to be produced as a 91-amino-acid precursor with a 33-amino-acid leader peptide, which is predicted to be removed, followed by joining of the N and C termini via a covalent linkage to form the mature 58-amino-acid circular bacteriocin PlcA. We report the characterization of a circular bacteriocin produced byLb. plantarum. The inhibition displayed againstA. acidoterrestrishighlights its potential use as a preservative in food and beverages.IMPORTANCEIn this work, we describe the purification and characterization of an antimicrobial peptide, termed plantaricyclin A (PlcA), produced by aLactobacillus plantarumstrain isolated from olives. This peptide has a circular structure, and all genes involved in its production, circularization, and secretion were identified. PlcA shows antimicrobial activity against different strains, includingAlicyclobacillus acidoterrestris, a common spoilage bacterium, which causes substantial economic losses in the beverage industry every year. In this study, we describe a circular antimicrobial peptide, PlcA, for aLactobacillus plantarumstrain.
Plantaricyclin A, a Novel Circular Bacteriocin Produced by Lactobacillus plantarum NI326: Purification, Characterization, and Heterologous Production
