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Applied and Environmental Microbiology, May 2006, p. 3383-3389, Vol. 72, No. 5
0099-2240/06/$08.00+0 doi:10.1128/AEM.72.5.3383-3389.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
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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