A novel bacteriocin-like substance (BLIS) from a pathogenic strain of Vibrio harveyi

School of Life Sciences, John Muir Building, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK Correspondence Brian Austin b.austin{at}hw.ac.uk Inter-strain and inter-species inhibition mediated by a bacteriocin-like inhibitory substance (BLIS) from a pathogenic Vibrio harveyi strain VIB 571 was demonstrated against four isolates of the same species, and one culture each of a Vibrio sp., Vibrio fischeri , Vibrio gazogenes and Vibrio parahaemolyticus . The crude BLIS, which was obtained by ammonium-sulphate precipitation of the cell-free supernatant of a 72 h broth culture of strain VIB 571, was inactivated by lipase, proteinase K, pepsin, trypsin, pronase E, SDS and incubation at 60 °C for 10 min. The activity was stable between pH 2–11 for at least 5 h. Anion-exchange chromatography, gel filtration, SDS-PAGE and two-dimensional gel electrophoresis revealed the presence of a single major peak, comprising a protein with a pI of 5·4 and a molecular mass of 32 kDa. The N-terminal amino acid sequence of the protein comprised Asp-Glu-Tyr-Ile-Ser-X-Asn-Lys-X-Ser-Ser-Ala-Asp-Ile (with X representing cysteine or modified amino acid residues). A similarity search based on the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) generated peptide masses and the N-terminal sequence did not yield any significant matches. Abbreviations: BLIS, bacteriocin-like inhibitory substance; CFS, cell-free supernatant; 2-DE, two-dimensional gel electrophoresis; DLPA, double-layer plate assay; MALDI-TOF-MS, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry A table of the bacterial isolates used in this study is available as suplementary data with the online version of the journal.