This may indicate that other virulence factors could be involved. Within this context, it will be of great interest to investigate new genes related to virulence in S. uberis. We thank M.V. Liliana Tirante (LactoDiagnóstico Sur, Olivos, Buenos Aires) for providing the isolates. This work was supported by grants from SECyT (Secretaría de Ciencia y Técnica, Universidad Nacional de Río Cuarto) and FONCyT

(Agencia Nacional de Promoción Científica y Tecnológica). S.A.D. is a fellow from CONICET and E.B.R. is a member assistant of the research career of CONICET. “
“Sakacin A was purified to homogeneity through simple chromatographic procedures from cultures of Lactobacillus sakei DSMZ 6333 grown on a low-cost medium. The highly purified protein dissipated both transmembrane potential (ΔΨ) and transmembrane pH gradient (ΔpH) in Listeria cells in a very intense, rapid, and energy-dependent EMD 1214063 ic50 fashion. On a slower timescale, purified sakacin A also showed a lytic activity

toward isolated cell walls of Listeria. Mass spectrometry was used to analyze the products of sakacin A action on cell walls, evidencing that sakacin A acts on various types of bonds within peptoglycans. Consumers are demanding high-quality foods, with minimal processing and low preservative levels (Batdorj et al., 2007). Natural and safe substances may represent an alternative to chemicals for inhibiting the growth of undesirable microorganisms. Bacteriocins from lactic acid bacteria can protect Crizotinib cell line food against spoilage or prevent growth of pathogenic bacteria (Cotter et al., 2005) and are rapidly digested by humans (Deraz et al., 2005). Class IIa bacteriocins are of the greatest interest, because of strong antimicrobial activity against Cyclin-dependent kinase 3 Listeria spp. This has stimulated investigation on rapid and cost-effective purification protocols and on functional characterization of these compounds. Standard purification methods include salt precipitation, followed by gel filtration, ion-exchange, and reverse-phase chromatography.

These methods are time-consuming and low-yielding (Guyonnet et al., 2000) and have been improved somewhat using cation-exchange chromatography (Berjeaud & Cenatiempo, 2004). Sakacin A is a class IIa bacteriocin produced by Lactobacillus sakei DSMZ 6333, able to inhibit the growth of several lactic acid bacteria and of Listeria monocytogenes. This bacteriocin is a small heat-stable protein with no posttranslational modifications (Schillinger & Lucke, 1989). All class IIa bacteriocins have a highly conserved N-terminal domain with the consensus motif YGNGV responsible for activity against Listeria (Richard et al., 2004). Upon exposure to these bacteriocins, leakage of ions and small molecules from sensitive cells accompanies dissipation of the proton motive force and depletion of intracellular ATP (Drider et al., 2006). We report here on: (1) purification of the bacteriocin produced by L.