Purification and characterization of adhesive exopolysaccharides from Pseudomonas putida and Pseudomonas fluorescens

In this study, the adhesive exopolysaccharides of strains of Pseudomonas putida and P. fluorescens, both isolated from freshwater epilithic communities, were examined with regard to their chemical composition, biosynthesis, and their role in adhesion. Electron microscopy showed that both strains were enrobed in fibrous glycocalyces and that these structures were involved in attachment of the cells to a solid surface and as structural matrices in the microcolony mode of growth. In batch culture experiments most of the extracellular polysaccharide of both strains was found to be soluble in the growth medium rather than being associated with bacterial cells. Exopolysaccharide was synthesized during all phases of growth, but when growth was limited by exhaustion of the carbon source, exopolysaccharide synthesis ceased whereas exopolysaccharide synthesis continued for some time after cessation of growth in nitrogen-limited cultures. Exopolysaccharide from both strains was isolated and purified. Pseudomonas putida synthesized an exopolysaccharide composed of glucose, galactose, and pyruvate in a ratio of 1:1:1; the P. fluorescens polymer contained glucose, galactose, and pyruvate in a ratio of 1:1:0.5, respectively. Polymers from both strains were acetylated to a variable degree.