Bacteriocins produced by lactic acid bacteria are a heterogeneous group of antibacterial proteins (12). Most bacte- riocins have narrow inhibitory spectra (4). Only a few of them have wider inhibitory spectra, being active against a wide range of bacteria (1, 6, 7). They exert their activity through adsorption to specific target molecules located on the external surface of sensitive bacteria, followed by metabolic, physiological, and morphological changes resulting in the death of the targeted bacteria (8). Major classes of bacteriocins produced by lactic acid bacteria include: (class I) lantibiotics, (class II) small heat-stable peptides, (class III) large heat-labile pro- teins, and (class IV) complex proteins whose activity requires the association of carbohydrate or lipid moieties (8, 12). Lactobacilli isolated from different eco- logical niches, such as the oral cavity, could be a source of new bacteriocin- producing probiotics. Probiotic microflora display numerous health benefits, such as the competitive exclusion of medically significant pathogens and the treatment and neutralization of side effects of antibiotic therapy (10, 11). In addition, they maintain cooperatively a delicate balance between the gastrointestinal tract and the immune system (3). One of the desirable properties of a probiotic strain is Oral Microbiology Immunology 2008: 23: 254–258 Printed in Singapore. All rights reserved Ó 2008 The Authors. Journal compilation Ó 2008 Blackwell Munksgaard Purification of bacteriocin LS1 produced by human oral isolate Lactobacillus salivarius BGHO1 Busarcevic M, Kojic M, Dalgalarrondo M, Chobert J-M, Haertle ´ T, Topisirovic L. Purification of bacteriocin LS1 produced by human oral isolate Lactobacillus salivarius BGHO1. Oral Microbiol Immunol 2008: 23: 254–258. Ó 2008 The Authors. Journal compilation Ó 2008 Blackwell Munksgaard. Introduction: Lactobacillus salivarius BGHO1, a human oral isolate with antagonistic activity against growth of Streptococcus mutans, Streptococcus pneumoniae, Staphylo- coccus aureus, Enterococcus faecalis, Micrococcus flavus, and Salmonella enteritidis, probably produces more than one proteinaceous antimicrobial substance. The objective of this study was the purification of a bacteriocin, named LS1, produced by L. salivarius BGHO1. Methods: A simple and fast procedure for bacteriocin purification was developed, consisting of reverse-phase chromatography of the ammonium sulfate precipitate of cell-free culture supernatant by fast protein liquid chromatography and high-performance liquid chromatography, followed by tricine sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), with the subsequent extraction of bacteriocin from the gel. Results: The supernatant of L. salivarius BGHO1 culture retained its antimicrobial activity after boiling in a water bath for 15 min. Its antimicrobial activity was also maintained even after treatment for 20 min at 121°C in an autoclave. Bacteriocin LS1 was purified to homogeneity. The molecular mass of bacteriocin LS1 was estimated to be approximately 10 kDa, based on tricine SDS-PAGE. During purification, another compound with antimicrobial activity, produced by L. salivarius BGHO1, was detected. The molecular mass of this compound was estimated to be approximately 5 kDa, based on tricine SDS-PAGE. Conclusion: Our results imply that LS1 is most probably a new bacteriocin, different from previously described bacteriocins produced by L. salivarius strains. The purification of bacteriocin LS1 enabled the further characterization of LS1 on both the molecular and genetic levels. M. Busarcevic 1 , M. Kojic 1 , M. Dalgalarrondo 2 , J.-M. Chobert 2 , T. Haertle ´ 2 , L. Topisirovic 1 1 Institute of Molecular Genetics and Genetic Engineering, Belgrade, Serbia, 2 UR 1268 Bio- polymers Interactions Assemblies, National Institute of Agronomic Research, Functions and Interactions of Dairy Proteins, Nantes, France Key words: bacteriocin; chromatography; human oral isolate; Lactobacillus salivarius Ljubisa Topisirovic, Institute of Molecular Genetics and Genetic Engineering, Vojvode Stepe 444/a, PO Box 23, 11010 Belgrade, Serbia Tel.: + 381 11 397 5960; fax: + 381 11 397 5808; e-mail: lab6@eunet.yu; topisir@eunet.yu Accepted for publication September 11, 2007