Surface properties of bifidobacterial strains of human origin

The adherence of Bifidobacterium strains isolated from infant feces and commercial fermented dairy products to enterocyte-like cells was correlated with the autoagglutination and hemagglutination properties of these organisms. These results allowed us to define two groups: (i) cell-adherent bacteria showing hemagglutination and autoagglutination and (ii) non-cell-adherent, nonhemagglutinating, nonautoagglutinating bacteria. Glass adherence was shown to be nonspecific and was discarded as a criterion for selection of adherent cells. Hydrophobicity appeared to be necessary for adhesion to enterocyte-like cells and autoagglutination. Adhesive strains were highly hydrophobic, and the degree of adherence was slightly dependent on the surface potential. Cells autoagglutinated more when the electrostatic negative charges on the cell surface were shielded by a decrease in the pH from 7 to 2. However, in some strains negative charges at the cell surface were adjuvant to adhesion, thus suggesting that specific chemical interactions occurred. The present results provide a method for preliminary selection of bacteria potentially adherent to epithelial cells by means of autoagglutination.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Criotecnología de Alimento

Volume recovery, surface properties and membrane integrity of Lactobacillus delbrueckii subsp. bulgaricus dehydrated in the presence of trehalose or sucrose

Aims: Although the practical importance of adding sugars before drying is well known, the mechanism of protection of bacteria by sugars is not clear. The response of the dehydrated micro-organisms to rehydration is analysed in terms of structural and functional changes, and correlated with their potentiality to grow in rich media. These aspects are related with the membrane integrity and the metabolic state of the rehydrated bacteria, measured by means of surface properties and permeability. To attain this objective, Lactobacillus delbrueckii subsp. bulgaricus was dehydrated in the presence and in the absence of sucrose and trehalose. The bacterial response upon rehydration was investigated by determining: (i) the lag time of the bacterial growing in rich media, (ii) the restoration of the surface properties and the cellular volume and (iii) the membrane integrity.Fil: Tymczyszyn, Emma Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Del Rosario Díaz, M.. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Gómez Zavaglia, A.. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Disalvo, Edgardo Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentin

A compact device for simultaneous dielectric spectroscopy and microgravimetric analysis under controlled humidity

Water plays a key role in the functioning of natural and synthetic molecular systems. Despite several hydration studies, different techniques are employed individually for monitoring different physical features such as kinetics, dynamics, and absorption. This study describes a compact hydration cell that enables simultaneous dielectric relaxation spectroscopy (DRS) and mass loss/uptake measurements in thin organic layers under controlled humidity conditions and in a wide temperature range. This approach enabled us to correlate the physical quantities obtained during the same experiment by complementary techniques. To demonstrate the performance of this device, a 200 nm thick poly(methyl methacrylate) (PMMA) layer was measured at various relative humidity levels (0%-75%), temperatures (25-75 °C), and frequencies (DRS: 0.1 Hz-1 MHz) to study how hydration and dehydration processes affect its molecular dynamics. The results show the capability of this setup to study the changes in the PMMA film regarding the kinetics and molecular dynamics upon variation of the water content.Fil: Gennaro, Alessia. Katholikie Universiteit Leuven; BélgicaFil: Rosa, Antonio Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Centro de Investigación en Biofísica Aplicada y Alimentos. - Universidad Nacional de Santiago del Estero. Centro de Investigación en Biofísica Aplicada y Alimentos; ArgentinaFil: Cornelis, Peter. Katholikie Universiteit Leuven; BélgicaFil: Pfeiffer, Helge. Katholikie Universiteit Leuven; BélgicaFil: Disalvo, Edgardo Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Centro de Investigación en Biofísica Aplicada y Alimentos. - Universidad Nacional de Santiago del Estero. Centro de Investigación en Biofísica Aplicada y Alimentos; ArgentinaFil: Wagner, Patrick. Katholikie Universiteit Leuven; BélgicaFil: Wübbenhorst, Michael. Katholikie Universiteit Leuven; Bélgic

Biological activity of antibacterial peptides matches synergism between electrostatic and non electrostatic forces

© 2013 Elsevier B.V. All rights reserved.Substitution of Ala 108 and Ala 111 in the 107–115 human lysozyme (hLz) fragment results in a 20-fold increased anti-staphylococcal activity while its hemolytic activity becomes significant (30%) at veryhigh concentrations. This analog displays an additional positive charge near the N-terminus (108) and anextra Trp residue at the center of the molecule (111), indicating that this particular amino acid sequenceimproves its interaction with the bacterial plasma membrane. In order to understand the role of thisarrangement in the membrane interaction, studies with model lipid membranes were carried out.The interactions of peptides, 107–115 hLz and the novel analog ([K108W111]107–115 hLz) with lipo-somes and lipid monolayers were evaluated by monitoring the changes in the fluorescence of the Trpresidues and the variation of the monolayers surface pressure, respectively. Results obtained with bothtechniques revealed a significant affinity increase of [K108W111]107–115 hLz for lipids, especially whenthe membranes containing negatively charged lipids, such as phosphatidylglycerol. However, there is alsoa significant interaction with zwitterionic lipids, suggesting that other forces in addition to electrostaticinteractions are involved in the binding. The analysis of adsorption isotherms and the insertion kineticssuggest that relaxation processes of the membrane structure are involved in the insertion process ofnovel peptide [K108W111]107–115 hLz but not in 107–115 hLz, probably by imposing a reorganization ofwater at the interphases.In this regard, the enhanced activity of peptide [K108W111]107–115 hLz may be explained by a syner-gistic effect between the increased electrostatic forces as well as the increased hydrophobic interactions.This work was supported with funds from Agencia Nacional de Promoción Cientiífica y Tecnológica, PICT 2007-757, PICT 2011-2606, CONICET (PIP 2011-2013 GI 11220100100484), UBACyT (20020090200663), (Programa-UNSE 23/A164), Fundação para a Ciência e a Tecnologia—Ministério da Educação e Ciência (FCT-MEC, Portugal), and FP7-PEOPLE IRSES (International Research Staff Exchange Scheme, European Union) project MEMPEPACROSS. EAD, NI, OC and AH are members of the Research Career of CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina). AB is recipient of a post doctoral fellowship of CONICET. AH is recipient of a post doctoral fellowship of FCT-MEC (SFRH/BPD/72037/2010). The authors thank Chemo-RomikinSA (Argentina) for use of their Peptide Synthesizer facilities