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Lactococcin Q, a Novel Two-Peptide Bacteriocin Produced by Lactococcus lactis QU 4

Laboratory of Microbial Technology, Division of Microbial Science and Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture,¹ Department of Functional Metabolic Design, Bio-Architecture Center, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan,² Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan³

Received 8 September 2005/ Accepted 28 February 2006

A bacteriocin-producing strain, Lactococcus lactis QU 4, was isolated from corn. The bacteriocin, termed lactococcin Q, showed antibacterial activity only against L. lactis strains among a wide range of gram-positive indicator strains tested. Lactococcin Q was purified by acetone precipitation, cation exchange chromatography, and reverse-phase chromatography. Lactococcin Q consisted of two peptides, and ß, whose molecular masses were determined to be 4,260.43 Da and 4,018.36 Da, respectively. Amino acid and DNA sequencing analyses revealed that lactococcin Q was a novel two-peptide bacteriocin, homologous to lactococcin G. Comparative study using chemically synthesized lactococcin Q (Q plus Qß) and lactococcin G (G plus Gß) clarified that hybrid combinations (Q plus Gß and G plus Qß) as well as original combinations showed antibacterial activity, although each single peptide showed no significant activity. These four pairs of lactococcin peptides acted synergistically at a 1:1 molar ratio and exhibited identical antibacterial spectra but differed in MIC. The MIC of Q plus Gß was 32 times higher than that of Q plus Qß, suggesting that the difference in ß peptides was important for the intensity of antibacterial activity.

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