Lactolisterin BU, a Novel Class II Broad-Spectrum Bacteriocin from Lactococcus lactis subsp. <i>lactis</i> bv. diacetylactis BGBU1-4

Abstract

<i>Lactococcus lactis</i> subsp. <i>lactis</i> bv. diacetylactis BGBU1-4 produces a novel bacteriocin, lactolisterin BU, with strong antimicrobial activity against many species of Gram-positive bacteria, including important food spoilage and foodborne pathogens, such as <i>Listeria monocytogenes</i>, <i>Staphylococcus aureus</i>, <i>Bacillus</i> spp., and streptococci. Lactolisterin BU was extracted from the cell surface of BGBU1-4 by 2-propanol and purified to homogeneity by C₁₈ solid-phase extraction and reversed-phase high-performance liquid chromatography. The molecular mass of the purified lactolisterin BU was 5,160.94 Da, and an internal fragment, AVSWAWQH, as determined by N-terminal sequencing, showed low-level similarity to existing antimicrobial peptides. Curing and transformation experiments revealed the presence of a corresponding bacteriocin operon on the smallest plasmid, pBU6 (6.2 kb), of strain BGBU1-4. Analysis of the bacteriocin operon revealed a leaderless bacteriocin of 43 amino acids that exhibited similarity to bacteriocin BHT-B (63%) from <i>Streptococcus ratti</i>, a bacteriocin with analogy to aureocin A.<b>IMPORTANCE</b> Lactolisterin BU, a broad-spectrum leaderless bacteriocin produced by <i>L. lactis</i> subsp. <i>lactis</i> bv. diacetylactis BGBU1-4, expresses strong antimicrobial activity against food spoilage and foodborne pathogens, such as <i>Listeria monocytogenes</i>, <i>Staphylococcus aureus</i>, <i>Bacillus</i> spp., and streptococci. Lactolisterin BU showed the highest similarity to aureocin-like bacteriocins produced by different bacteria. The operon for synthesis is located on the smallest plasmid, pBU6 (6.2 kb), of strain BGBU1-4, indicating possible horizontal transfer among producers.