lipoteichoic-acid and n-hexadecane

The involvement of the cell wall in the acquisition of nisin resistance by Listeria monocytogenes F6861 and its nisin-resistant mutant was investigated. Results indicated that without a cell wall, the acquired nisin resistance of the mutant was lost. Cell surface hydrophobicity was shown to correlate with nisin sensitivity; the wild type strain being more hydrophobic than its mutant. The possible role of S-layer proteins in nisin resistance was investigated. Examination of strains by freeze-etching and atomic force microscopy did not demonstrate the presence of S-layers in either strain while SDS-PAGE following S-layer extraction procedures revealed no major protein bands. Chloramphenicol did not adversely affect the frequency of isolation of nisin-resistant mutants, indicating that de novo protein synthesis was not involved. The involvement of other cell surface components, teichoic and lipoteichoic acids, was also examined. In contrast with other reports, comparison of the total phospholipid content of the mutant with its parental strain showed no significant difference (P > 0.05).

Topics: Alkanes; Anti-Bacterial Agents; Bacterial Adhesion; Bacterial Outer Membrane Proteins; Cell Wall; Chloramphenicol; Drug Resistance, Microbial; Lipopolysaccharides; Listeria monocytogenes; Mutation; Nisin; Phospholipids; Protein Synthesis Inhibitors; Protoplasts; Teichoic Acids

Berberine sulfate is an alkaloid extracted from the roots and bark of various plants and possesses antibacterial, antifungal, and antiprotozoal activities. Most studies have focused on the bacteriostatic or bactericidal activities of this compound. In this study, we report that berberine sulfate is bacteriostatic for streptococci and that sub-MICs of berberine blocked the adherence of streptococci to host cells, immobilized fibronectin, and hexadecane. Concentrations of berberine below its MIC caused an eightfold increase in release of lipoteichoic acid from the streptococci. Higher concentrations of berberine directly interfered with the adherence of streptococci to host cells either by preventing the complexing of lipoteichoic acid with fibronectin or by dissolution of such complexes once they were formed. Thus, berberine sulfate interferes with the adherence of group A streptococci by two distinct mechanisms: one by releasing the adhesin lipoteichoic acid from the streptococcal cell surface and another by directly preventing or dissolving lipoteichoic acid-fibronectin complexes.

Topics: Alkanes; Bacterial Adhesion; Berberine; Berberine Alkaloids; Epithelial Cells; Epithelium; Fibronectins; Hemagglutination Tests; Humans; Lipopolysaccharides; Microbial Sensitivity Tests; Streptococcus pyogenes; Teichoic Acids

The effect of human plasma fibronectin on the adherence of Streptococcus pyogenes to hexadecane droplets was investigated. Fibronectin blocked the adherence of streptococci to hexadecane in a dose-dependent manner. The inhibitory effect resulted from the binding of fibronectin to the streptococcal cells; radiolabeled fibronectin failed to bind to the hexadecane but bound readily to untreated streptococci. Chemical treatments of streptococci that decreased streptococcal binding of fibronectin also decreased their binding to hexadecane. Pretreatment of fibronectin with lipoteichoic acid blocked the binding of fibronectin to streptococci and abolished its ability to inhibit streptococcal adherence to hexadecane in a dose-related manner. In contrast, wheat germ agglutinin, which binds to N-acetylglucosamine on the surface of S. pyogenes cells, failed to alter hexadecane adherence. The data suggest that fibronectin binds to lipoteichoic acid on the surface of the streptococci, thereby preventing lipoteichoic acid from interacting with the hexadecane phase.

Topics: Alkanes; Fibronectins; Humans; Lipopolysaccharides; Phosphatidic Acids; Protein Binding; Streptococcus pyogenes; Teichoic Acids

The adherence of Streptococcus pyogenes cells to hexadecane droplets was measured by vortexing water suspensions of streptococci with hexadecane. It was found that adherence of the organisms to hexadecane droplets was abolished by pretreating the organisms with trypsin, pepsin at pH 4.5, or HCl solutions at 95 degrees C. Streptococcal adherence was best expressed in organisms harvested during the stationary phase of growth and was inhibited by fatty acid-free albumin because of the interaction of the protein with the streptococcal surfaces. The data suggest that adherence to hexadecane droplets measures the availability on the surface of S. pyogenes cells of lipophilic residues that are either hydrophobic regions of surface protein structures or, more likely, glycolipids complexed with and oriented by surface proteins.

Topics: Adhesiveness; Adsorption; Alkanes; Antigens, Bacterial; Bacterial Outer Membrane Proteins; Bacterial Proteins; Carrier Proteins; Hydrochloric Acid; Lipopolysaccharides; Pepsin A; Phosphatidic Acids; Streptococcus pyogenes; Teichoic Acids; Trypsin