Bacterial Cell Walls and Surfaces

Wicken, A. J.

doi:10.1007/978-1-4615-6514-7_2

Cited by 58 publications

(39 citation statements)

References 69 publications

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“…The P/C ratios of the eight E. coli strains were higher than those of oral streptococci, but lower than those of staphylococci ( Table 4). The rather high P/C ratios of E. coli might be explained by the relatively high content of phospholipids in the outer membrane of this gram-negative organism (32). The difference in P/C ratios between the staphylococci and streptococci is in agreement with the high PI/CH ratio found for the staphylococci and the low PI/CH ratio in streptococci.…”

Section: Harkes Et Alsupporting

confidence: 72%

Physicochemical characterization ofEscherichia coli

et al. 1992

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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 OR). 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 *Author to whom all correspondence and reprint requests should be addressed. Cell Biophysics 1 7Volume 20, 1992 18Harkes et al.(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-negative E. 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.

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Section: Harkes Et Alsupporting

confidence: 72%

Physicochemical characterization ofEscherichia coli

et al. 1992

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“…Understanding these complex functions requires detailed knowledge of the elemental, molecular, and structural composition of the cell surface, which is obviously different from the bulk of the cell wall (3,18). Generally such knowledge is obtained by electron microscopic methods, by probing the cell surface with specific molecules such as antibodies or lectins, by functional tests such as hydrophobicity assays, or by indirect techniques involving the removal of surface components (8,12).…”

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confidence: 99%

Surface properties of Streptococcus salivarius HB and nonfibrillar mutants: measurement of zeta potential and elemental composition with X-ray photoelectron spectroscopy

et al. 1988

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To characterize the functional cell surface, the zeta potentials and elemental surface composition of Streptococcus salivarius HB and a range of mutants with known molecular surface structures were determined. Zeta potentials of fully hydrated cells were measured as a function of pH in dilute potassium phosphate solutions, yielding isoelectric points of the strains. Elemental composition (0, C, N, and P) of the outer 2 to 5 nm of the freeze-dried cell surfaces were measured by X-ray photoelectron spectroscopy. An increasing loss of proteinaceous fibrillar surface antigens of the mutants was found to be accompanied by a progressive decrease in the N/C ratio from 0.104 in the parent strain HB to 0.053 in mutant HBC12. Simultaneously, the value of the isoelectric point shifted from 3.0 to 1.3. In a previous study (A. H. Weerkamp, H. C. van der Mei, and J. W. Slot, Infect. Immun. 55:438-455, 1987) on the cell surfaces of the same strains, it was shown that removal of fibrils led to increased exposure of (lipo)teichoic acid at the surface, which explains the low isoelectric point caused by the low pKa of the phosphate groups.The outer surface of bacterial cells mediates many crucial interactions of the cells with their environment, such as adherence, flocculation, antigenicity, susceptibility to phagocytosis, and binding of macromolecules. Understanding these complex functions requires detailed knowledge of the elemental, molecular, and structural composition of the cell surface, which is obviously different from the bulk of the cell wall (3, 18). Generally such knowledge is obtained by electron microscopic methods, by probing the cell surface with specific molecules such as antibodies or lectins, by functional tests such as hydrophobicity assays, or by indirect techniques involving the removal of surface components (8,12).Only a few techniques provide information on the chemical composition on the outer surface of intact cells. An elemental analysis over the thickness of the outer 2 to 5 nm can be obtained by X-ray irradiation of surfaces, causing ejection of electrons, which can be discriminated by their binding energy in a specific chemical element. X-ray photoelectron spectroscopy (XPS) is most frequently used for nonbiological surfaces but has been used in a few cases for the study of bacterial and eucaryotic cells (2, 7, 13). Compared with other surface techniques (1), XPS has the advantage of being nondestructive and highly surface sensitive; it gives a high information content and yields quantitative data on elemental composition and chemical bonding. A disadvantage, common to most analytical surface techniques, is that samples must be measured under high vacuum (10-6 to 10-9 Pa).Previously, we studied the structure and molecular composition of the cell surface of Streptococcus salivarius HB and a range of mutants devoid of specific fibrillar appendages and lacking adhesive abilities (11,17). No information is * Corresponding author. available on the elemental surface composition of these cells and how it w...

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“…LTAs similarly form high-molecular-weight aggregates or presumptive micelles in aqueous solution, as judged by their behavior on gel chromatography (9,29,35). Treatment with detergents reduces the high-molecular-weight aggregates to what is presumed to be a monomeric form (9).…”

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Critical micelle concentrations of lipoteichoic acids

Wicken¹,

Evans²,

Knox³

1986

J Bacteriol

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Purified lipoteichoic acids (LTAs) from several gram-positive organisms have been shown, by methods involving spectral changes of an added merocyanine dye probe, to have critical micelie concentrations in the range of 1 to 10 jig/ml, suggesting that acylated LTAs in their monomer forms may represent the major configuration of extracellular LTAs in bacterial culture fluids. The critical micelle concentrations obtained did not differ markedly with degree of carbohydrate substitution of the polymers. The significance of these findings in relation to the biological properties of LTA is discussed.Lipoteichoic acid (LTA) is the generic name given to a group of structurally related amphipathic molecules or amphiphiles found as cell membrane components in a wide range of gram-positive bacteria. The hydrophilic portion of the molecule is typically a 1,3-phosphodiester-linked polymer of glycerophosphate, variously substituted in the C-2 position of the glycerol residues with sugars in glycosidic linkage and D-alanine in ester linkage. The hydrophobic region of the molecule, linked covalently through the phosphomonoester end of the polymer, is generally either a glycolipid or phosphatidylglycolipid. This lipid "end" is intercalated with the upper half of the bilayer of the cell membrane and provides a membrane anchor for the molecule. LTA is also found as a soluble excreted product in cultures of gram-positive bacteria (29, 35).In aqueous solution, amphipathic molecules or amphiphiles tend to form micellar aggregates to occlude water from the hydrophobic regions of their molecular structure. LTAs similarly form high-molecular-weight aggregates or presumptive micelles in aqueous solution, as judged by their behavior on gel chromatography (9,29,35). Treatment with detergents reduces the high-molecular-weight aggregates to what is presumed to be a monomeric form (9). In any solution of an amphiphile, the micellar form must coexist with monomer. environment (10,25,26). Merocyanine dyes are among the more thoroughly characterized of the various types of compounds used as indicators of solvent polarities. With change in solvent polarities, their electronic spectra can show very large shifts in their absorption bands or intensity of fluorescence which in turn are presumed to be due to changes in the balance of benzenoid and quinonoid valence structure of the probe (4). The merocyanine dye most commonly used in such studies is 4-[2-(1-methyl-1,4,dihydropyridin-4-ylidene)ethylidene] cyclohexa-2-5-dien-1-one, which shows a shift in the UV-visible absorption spectrum towards longer wavelength as the solvent polarity decreases (5). More recently, an amphipathic merocyanine dye has been synthesized in which the methyl group has been replaced by a hexadecyl chain (8), thereby increasing its hydrophobic character and favoring its solubilization by micelles. Studies with this probe showed upward wavelength shifts in its absorption spectrum in solutions of various detergents as the concentrations of the latter were increased from below to ...

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Bacterial Cell Walls and Surfaces

Cited by 58 publications

References 69 publications

Physicochemical characterization ofEscherichia coli

Physicochemical characterization ofEscherichia coli

Surface properties of Streptococcus salivarius HB and nonfibrillar mutants: measurement of zeta potential and elemental composition with X-ray photoelectron spectroscopy

Critical micelle concentrations of lipoteichoic acids

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