Polymer interactions between five gram-negative bacteria and glass investigated using LPS micelles and vesicles as model systems

Abstract

The contributions to bacterial adhesion of the lipopolysaccharides (LPS) as the outermost cell surface constituents of Gram-negative bacteria were investigated. Adhesion of five Gram-negative bacterial strains to glass and adsorption of purified LPS of these bacteria to SiO 2, TiO 2, and Al 2O 3 were studied in percolated columns and in batch sorption experiments, respectively. Physicochemical characteristics of bacteria, LPS, and solid surfaces were used to calculate DLVO and hydrophobic interaction forces. Stenotrophomonas maltophilia DSM 50170 possesses two types of LPS: only 0.5% of the LPS carry a long polysaccharide chain (length≈30 nm), whereas the remaining 99.5% carry a short chain (length≈1 nm). The irreversible adhesion of this bacterium may be explained by the attractive interactions of the long polysaccharides with the solid surface (bridging). The densely arranged long LPS of the other four bacteria may be responsible for strong repulsion which exceeded the attractive interactions that were observed with the isolated LPS of these strains and the solid surfaces. The polysaccharide structures of the O-antigens differed considerably between the five bacteria. Information of the chemical structure of O-antigen monomers, the composition of repeating units, the presence of branched or straight O-antigens, or the length of the O-antigens, was not sufficient to allow prediction of the adsorption behaviour of isolated LPS.