Lactococcin MMFII, a novel class IIa bacteriocin produced by Lactococcus lactis MMFII, isolated from a Tunisian dairy product

A novel bacteriocin, lactococcin MMFII, produced by Lactococcus lactis MMFI I isolated from a Tunisian dairy product had been identified. The bacterioc in was purified to homogeneity from fresh overnight M17 broth culture by su lfate ammonium precipitation. cation-exchange chromatography, sep-park chro matography and two steps of reverse-phase chromatography. The purified bact eriocin was heat stable, pH resistant and protease sensitive. Its amino aci d sequence. obtained by Edman degradation, revealed a 37-amino acid peptide with two cysteine residues in positions 9 and 14 and a calculated mass of 4144.6 Da. Laser desorption mass spectrometry analysis gave a molecular mas s of 4142.6, suggesting the presence of a disulfide bond within the purifie d bacteriocin. Lactococcin MMFII contains the N-terminal YGNGV consensus mo tif and is active against Listeria. Thus. it belongs to the class IIa bacte riocins figuring the first example of such a bacteriocin produced by a lact ococcal strain. (C) 2001 Federation o European Microbiological Societies. P ublished by Elsevier Science B.V. All rights reserved.