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Isolation and characterization of a new bacteriocin from Lactobacillus gasseri KT7

Zhu, W.M., Liu, W., Wu, D.Q.
Journal of applied microbiology 2000 v.88 no.5 pp. 877-886
Clostridium, Enterococcus, Lactobacillus gasseri, Listeria, amino acid composition, amino acids, ammonium sulfate, antibacterial properties, antimicrobial peptides, bacteriocins, cation exchange chromatography, enzymes, feces, food spoilage, fractionation, heat tolerance, hydrophobicity, lactic acid bacteria, pH, polyacrylamide gel electrophoresis, proteolysis, reversed-phase high performance liquid chromatography, reversed-phase liquid chromatography
A bacteriocin-producing Lactobacillus gasseri strain, KT7, was isolated from infant faeces. The supernatant fluid showed inhibitory activity not only against some lactic acid bacteria but also, against some pathogenic and food-spoilage species, including Clostridium, Listeria and Enterococcus. An antimicrobial peptide designated gassericin KT7 was isolated from Lactobacillus gasseri KT7. It was purified to homogeneity by a single four-step procedure: a crude supernatant fluid obtained from early stationary-phase culture in MRS medium was subjected to ammonium sulphate fractionation, CM-Sephadex cation-exchange chromatography, Phenyl-Sepharose hydrophobic chromatography and reverse-phase HPLC chromatography. Gassericin KT7 was sensitive to proteolytic enzymes, resistant to heat, active over a wide range of pH, and migrated as a 4.5-5.0 kDa peptide on SDS-PAGE. The bacteriocin was produced constitutively during exponential growth. It was bactericidal to sensitive cells and the bactericidal effect was not produced by cell lysis. The amino acid composition of the bacteriocin was determined and no modified amino acid was found among the residues identified.