Structure of the acidic extracellular gelling polysaccharide produced by Pseudomonas elodea

The gelling polysaccharide secreted by the bacterium Pseudomonas elodea contains l-rhamnose, d-glucose, and d-glucuronic acid in the molar ratios 1:2:1. Methylation analysis of native and carboxyl-reduced polysaccharide indicated (1→4)-Rhap, (1→3)-Glcp, (1→4)-Glcp, and (1→4)-GlcpA to be present in the ratios 1:1:1:1. Graded acid hydrolysis gave a series of acidic oligosaccharides that were isolated by ion-exchange chromatography and fractionated by gel-filtration. The purified oligosaccharides were analysed and characterised as their methylated alditol derivatives by e.i.-m.s. and c.i.-m.s., and also examined by fast-atom-bombardment (f.a.b.)-m.s. The tetrasaccharide repeating-unit 1, excluding acetyl groups, is proposed.