THE STRUCTURE OF THE ACIDIC EXOPOLYSACCHARIDE PRODUCED BY PSEUDOMONAS-GINGERI STRAIN PF9

The structure of the acidic exopolysaccharide produced by the mushroom pathogen Pseudomonas ''gingeri'' strain Pf9, a bacterium which causes ginger blotch, was investigated by chemical analysis, mass spectromet ry and 1D and 2D NMR spectroscopy. The polysaccharide consists of the linear trisaccharide repeating unit [GRAPHICS] where the cyclic pyruvi c acetal groups at O-4 and O-6 of the mannopyranosyl residues have the S-configuration. Methylation analysis under neutral conditions and NM R data showed that the mannose residues are acetylated at O-2. This ex opolysaccharide has the same structure as the E. coli K55 capsular pol ysaccharide and differs from the Klebsiella K5 capsular polysaccharide only in the position of acetylation (C-2 of the glucopyranose residue ).