Food Sci. Biotechnol. 20(2): 289-296 (2011) DOI 10.1007/s10068-011-0041-6 Genetic Determination and Localization of Multiple Bacteriocins Produced by Enterococcus faecium CWBI-B1430 and Enterococcus mundtii CWBI-B1431 Ana Aguilar-Galvez, Robin Dubois-Dauphin, David Campos, and Philippe Thonart Received: 2 April 2010 / Revised: 21 November 2010 / Accepted: 22 November 2010 / Published Online: 30 April 2011 © KoSFoST and Springer 2011 Abstract Enterococcus faecium CWBI-B1430 and Enterococcus mundtii CWBI-B1431 from artisanal- produced Peruvian cheeses showed the presence of 4 putative bacteriocin genes: enterocin A, enterocin B, enterocin P, and mundticin KS. The multiple bacteriocin producer E. faecium CWBI-B1430 presented 1 plasmid of 34.6 kb, whereas E. mundtii CWBI-B1431 contained 1 plasmid of 11.0 kb. The structural gene responsible for mundticin KS production was located on 5.6 and 3.1 kb HindIII plasmid fragments. The reverse transcription-PCR analysis showed the expression of the bacteriocin genes enterocin A, enterocin B, and mundticin KS in E. faecium CWBI-B1430 and the bacteriocin genes enterocin P and mundticin KS in E. mundtii CWBI-B1431. To our knowledge, this is the first report of the expression of mundticin KS in E. faecium and enterocin P in E. mundtii. Keywords: Enterococcus faecium, Enterococcus mundtii, enterocin P, mundticin KS, genetic expression Introduction Genus Enterococcus is ubiquitous in nature, but the role it plays is often unclear (1). Enterococci are found in vegetables, plant material, and food, especially those of animal origin, such as dairy products (2). Enterococci are lactic acid bacteria (LAB). LAB are involved in food processing; they improve the shelf-life and safety of spontaneous fermentation products by producing several antibacterial compounds, including lactic and organic acids, ethanol, hydrogen peroxide, carbon dioxide, diacetyl, and bacteriocins (3,4). Bacteriocins are small, cationic, amphiphilic, antimicrobial peptides that vary in spectrum of action, mode of action, molecular structure, molecular mass, thermostability, pH range of activity, and genetic determinants (5). The production of bacteriocin by enterococci is referred to as enterocin. Enterocins are important because of their diversity and their exceptional distribution among isolates from different sources. Franz’s classification a simplified classification scheme for enterocins based on amino acid sequence homologies (6). Enterocins belong to class I, lantibiotic; class II, enterocins of the pediocin family synthesized without a leader peptide and other linear non pediocin-like enterocins; class III, cyclic antibacterial peptides; and class IV, large proteins. Enterocins are particularly active against pathogenic bacteria such as Listeria monocytogenes, Sthapylococcus aureus, and Clostridium spp. (7). The production of multiple bacteriocins by a single strain and the extract of the same enterocins from diverse strains were observed. Previous studies have demonstrated that Enterococcus faecium CWBI-B1430 and Enterococcus mundtii CWBI- B1431 isolated from artisanal-produced Peruvian cheeses produce a bacteriocin-like substance that can be classified as a class II enterocin (8). These studies have focused on the screening of bacteriocin genes in E. faecium CWBI- B1430 and E. mundtii CWBI-B1431. Once these enterocin genes were identified, their localization and expression were studied. The influence of growth temperature (12 to 42 o C) on the bacteriocin expression was determined. Ana Aguilar-Galvez, David Campos ( ) Universidad Nacional Agraria La Molina, Instituto de Biotecnología. Av. La Molina s/n. Lima, Perú Tel: +511-3495764; Fax: +511-3495764 E-mail: dcampos@lamolina.edu.pe Ana Aguilar-Galvez, Robin Dubois-Dauphin, Philippe Thonart University of Liège, Gembloux Agro-Bio Tech. Unit of Bio-Industry. Passage des Déportés 2, B-5030 Gembloux, Belgium RESEARCH ARTICLE