Biomedical subjects

Graciela Vignolo

Publications and source records attributed to Graciela Vignolo.

3 recordsLinked to original sources

PubMed2004

Meat-model system development for antibacterial activity determination.

Bacteriocins are antibacterial substances produced by many different bacterial species. Although the bacteriocins form a heterogenous group with respect to production of bacteria, antibacterial spectrum, mode of action, and chemical properties, they are by definition proteinaceous compounds that are bactericidal toward organisms taxonomically close to the producer. The ability of lactic acid bacteria (LAB) to compete and finally dominate in mixed fermentations has been attributed to the production of several antimicrobial metabolites such as organic acids, carbon dioxide, hydrogen peroxide, diacetyl, and bacteriocins. The antimicrobial activities of the LAB have long been known, but their bacteriocins have received limited attention until recently. Numerous strains of lactic acid bacteria associated with food systems are capable of producing bacteriocins, or antibacterial proteins with activity against foodborne pathogens and contaminants. Recently, considerable enphasis has been placed on the physicochemical, biochemical, and genetic characterization of these proteins. Many methods for the detection of bacteriocin production as well as the determination of the potency of bacteriocin preparations have been described. All the usual techniques are based on the fact that bacteriocins can diffuse in solid or semisolid culture media, which are subsequently inoculated with a suitable indicator strain. This method has long been shown to have a good perfomance in the characterization of new bacteriocins. Although results obtained from broth systems show that bacteriocins inhibit target organisms, applied studies must be performed to confirm their effectiveness in food. As many lactic acid bacteria associated with meat products were described to be important natural bacteriocin producers, it has been necessary to assay their inhibitory efficacy in meat or meat products. Because of the complexity of these kinds of foods a simplified meat-model system was developed to determine the inhibitory activity of a bacteriocin.

Animals↗

PubMed2004

Meat-model system development for proteolytic activity determination.

Many technological parameters that affect the nature and functional properties of proteins are involved in the preparation of meat products. The dry-curing process is quite complex because of the coexistence of enzymes from endogenous and bacterial origins. The protein breakdown that takes place during the ripening of dry fermented sausages leads to an increase in the concentration of peptides and free amino acids. The proteolytic events have been thoroughly investigated not only because of their physiological significance but also for their technological connotations in terms of texture and flavor development. Lactic acid bacteria and Staphylococcus or Kocuria are used as starter cultures in fermented meat products. In recent years, the proteolytic system of lactobacilli involved in meat fermentation became the focus of an increasing number of studies because of the technological roles of these organisms. Although results obtained from broth systems show proteolytic activity, studies involving food systems must be done to confirm their effectiveness. A simplified soluble muscle extract to determine the capacity to degrade meat proteins by lactic acid bacteria was developed using a spectrophotometric method based on the reaction of the alpha-amino groups released by hydrolysis with o-phtaldialdehyde and beta-mercaptoethanol to form an adduct (1-thioalkyl-2-alkylisoindoles) that is enhanced at basic pH and absorbs strongly at 360 nm.

Animals↗

PubMed2003

Mode of action of lactocin 705, a two-component bacteriocin from Lactobacillus casei CRL705.

Lactocin 705 is a bacteriocin whose activity depends on the complementary action of two peptides (705alpha and 705beta) of 33-amino-acid residues each and is produced by Lactobacillus casei CRL705. Biologically active, synthetic lactocin 705 was used to study the mode of action on sensitive cells of Lactobacillus plantarum CRL691. The addition of 90 nmol l(-1) of lactocin 705 to cells of L. plantarum dissipated both, the membrane potential (DeltaPsi) and the pH gradient (DeltapH). Energized membrane, obtained after the addition of glucose, were more susceptible to lactocin 705 action leading to the immediate release of intracellular K(+) and inorganic phosphate. When the role of various ions on sensitive cells were analyzed, only Ca(2+) ion exhibited a protective effect against lactocin 705. These data suggest that the presence of a proton motive force (PMF) promotes the interaction of the bacteriocin with the cytoplasmic membrane of energized cells, leading to pore formation which allows for the efflux of ions, thereby ensuring efficient killing of target bacteria.

Bacteriocins↗