Influence of electrical properties on the evaluation of the surface hydrophobicity of Bacillus subtilis

The surface hydrophobicity of nine Bacillus subtilis strains in different states (spores, vegetative cells, and dead cells) was assessed by water contact angle measurements, hydrophobic interaction chromatography (HIC) and bacterial adhesion to hydrocarbon (BATH). Electrokinetic properties of B, subtilis strains were characterized by zeta potential measurements and found to differ appreciably according to the strain, Correlations between HIC data, BATH data and zeta potential showed that HIC and RATH are influenced by electrostatic interactions. Water contact angle measurements thus provide a better estimate of cell surface hydrophobicity. The water contact angle of B. subtilis varied according to the strain and the state, the spores tending to be more hydrophobic than vegetative cells. (C) 2001 Elsevier Science B.V. All rights reserved

Characterization of eukaryotic cell surfaces prior to and after serum protein adsorption by X-ray photoelectron spectroscopy - Fibroblasts, HELA epithelial, and smooth muscle cells

Elemental surface concentration ratios N/C, O/C, and P/C of fibroblasts, HELA epithelial cells, and smooth muscle cells, prior to and after washing in the absence or presence of serum proteins, were determined by X-ray photoelectron spectroscopy. Cell surfaces appeared to adsorb hardly any serum proteins, and the relatively high P/C, as compared to N/C and O/C, elemental surface concentration ratio indicated that the cell surfaces consisted mainly of the phospholipid bilayer, with little or no proteins present. The lack of adsorption of serum proteins to the cell surfaces seems at odds with the common notion that cells require adhesive proteins in order to adhere and spread. However, the adsorption behavior of cellularly produced proteins may be completely different, particularly since they seem to be able to displace adsorbed serum proteins from biomaterials surfaces. Interestingly, only HELA epithelial cells (a tumor cell line) appeared to adsorb a very small amount of proteins.</p

Physicochemical characterization of Escherichia coli:A comparison with gram-positive bacteria

Eight Escherichia coli strains were characterized by determining their adhesion to xylene, surface free energy, zeta potential, relative surface charge, and their chemical composition. The latter was done by applying X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). No relationship between the adhesion to xylene and the water contact angles of these strains was found. Three strains had significantly lower surface free energies than the other strains. Surface free energies were either obtained from polar and dispersion parts or from Lifshitz-van der Waals and acid/base parts of the surface free energy. A correlation (r=0.97) between the polar parts and the electron-donor contributions to the acid/base part of the surface free energy was found. The zeta potentials of all strains, measured as a function of pH (2–11), were negative. Depending on the zeta potential as a function of pH, three groups were recognized among the strains tested. A relationship (r=0.84) was found between the acid/base component of the surface free energy and the zeta potential measured at pH=7.4. There was no correlation between results of XPS and IR studies. Data from the literature of XPS and IR studies of the gram-positive staphylococci and streptococci were compared with data from the gram-negativeE. coli used in this study. It appeared that in these three groups of bacteria, the polysaccharide content detected by IR corresponded well with the oxygen-to-carbon ratio detected by XPS

Imaging the nanoscale organization of peptidoglycan in living Lactococcus lactis cells

Peptidoglycans provide bacterial cell walls with mechanical strength. The spatial organization of peptidoglycan has previously been difficult to study. Here, atomic force microscopy, together with cells carrying mutations in cell-wall polysaccharides, has allowed an in-depth study of these molecules

Contribution des différentes fonctions chimiques dans les bandes d'absorption infrarouge des kérogènes situées à 1710, 1630 et 3430 cm -1

Afin d'estimer la contribution de divers groupes fonctionnels dans certaines bandes d'absorption infrarouge des kérogènes, on a mesuré les variations de coefficient d'absorption que provoquent des traitements chimiques affectant spécifiquement les groupements concernés. Les traitements visant à transformer les hydroxyles, responsables de labande à 3 430 cm-I, se sont révélés peu efficaces; par contre l'étude portant sur deux autres bandes a été plus fructueuse. On peut déterminer la contribution des groupements carbonyles, acides et esters dans la bande à 1710 cm-1. On peut également estimer la contribution de l'eau moléculaire, des carbonyles quinoniques, des insaturations oléfiniques et des vibrations de noyaux aromatiques dans la bande à 1630 cm-1. On dispose ainsi d'une méthode de caractérisation des kérogènes qui peut être mise en oeuvre pour affiner leur analyse chimique et fournir une sorte d'analyse fonctionnelle. La méthode présentée ne consomme que peu de produit; elle est directe, assez rapide et se prête bien à une étude comparative de séries d'échantillons

Surface properties of top- and bottom-fermenting yeast.

The surface physico-chemical properties (hydrophobicity, electrophoretic mobility, chemical composition) of a large set of top- and bottom-fermenting brewing yeasts, harvested in the exponential and stationary growth phases, have been investigated. Bottom- and top-fermenting strains showed different surface properties. Top strains were generally more hydrophobic than bottom strains, due to higher surface protein concentrations. Bottom strains possessed higher surface phosphate concentrations. The different profiles of electrophoretic mobility versus pH for top and bottom strains could be explained by modelling the surface charge according to the surface chemical composition as given by X-ray photoelectron spectroscopy. For bottom strains, the electrical properties were mainly controlled by phosphate, resulting in a low isoelectric point (pH 2 or below) and an electrophoretic mobility that did not become much more negative above pH 4. For the top strains, they were mainly determined by the balance of protonated amino- and carboxylate groups in proteins, which gave a high isoelectric point (pH 4) and an electrophoretic mobility changing greatly with pH in the range of 2 to 7. No difference in surface properties was found between flocculating and non-flocculating strains, or between cells from the exponential and stationary growth phases, even for strains where flocculation occurred during the transition from one growth phase to the other

Variation of the surface properties of Bacillus licheniformis according to age, temperature and aeration.

The surface properties of Bacillus licheniformis DSM 603 have been examined as a function of age during cultures in baffled and non-baffled Erlenmeyer flasks, at 30 and 37 degrees C. The elemental composition of the surface was determined by X-ray photoelectron spectroscopy and its variation was compared with the electrophoretic mobility and water contact angle. The variations of the surface phosphate concentration during the cultures and according to growth conditions indicate that the determining factor is the total cell concentration. The P/C atomic concentration ratio remains in a range where its variation does not influence the electrophoretic mobility. The decrease and increase of hydrophobicity during cultures at 30 degrees C in baffled and normal flasks, respectively, are paralleled by a variation in the O/C ratio

Surface of Lactic Acid Bacteria: Relationships between Chemical Composition and Physicochemical Properties

The surface chemical composition and physicochemical properties (hydrophobicity and zeta potential) of two lactic acid bacteria, Lactococcus lactis subsp. lactis bv. diacetilactis and Lactobacillus helveticus, have been investigated using cells harvested in exponential or stationary growth phase. The surface composition determined by X-ray photoelectron spectroscopy (XPS) was converted into a molecular composition in terms of proteins, polysaccharides, and hydrocarbonlike compounds. The concentration of the last was always below 15% (wt/wt), which is related to the hydrophilic character revealed by water contact angles of less than 30°. The surfaces of L. lactis cells had a polysaccharide concentration about twice that of proteins. The S-layer of L. helveticus was either interrupted or crossed by polysaccharide-rich compounds; the concentration of the latter was higher in the stationary growth phase than in the exponential growth phase. Further progress was made in the interpretation of XPS data in terms of chemical functions by showing that the oxygen component at 531.2 eV contains a contribution of phosphate in addition to the main contribution of the peptide link. The isoelectric points were around 2 and 3, and the electrophoretic mobilities above pH 5 (ionic strength, 1 mM) were about −3.0 × 10(−8) and −0.6 × 10(−8) m(2) s(−1) V(−1) for L. lactis and L. helveticus, respectively. The electrokinetic properties of the latter reveal the influence of carboxyl groups, while the difference between the two strains is related to a difference between N/P surface concentration ratios, reflecting the relative exposure of proteins and phosphate groups at the surface