Exopolysaccharides of the phytopathogen Pseudomonas syringae pv. glycinea

Exopolysaccharides (EPS) of the soybean pathogen Pseudomonas syringae pv. glycinea were isolated from culture filtrates and infected soybean leaves. Levan (a polyfructan with a C-2----C-6 backbone and C-2----C-1 branching) or acetylated alginate (a linear polyuronide of C-1----C-4-linked mannuronic and guluronic acids) was isolated from culture filtrates when bacterial strains were grown in a semisynthetic medium containing sucrose or glucose, respectively, as the primary carbon source. Acetylated alginate was the only EPS isolated from soybean [Glycine max (L.) Merr.] leaves inoculated with compatible (disease-inducing) strains of P. syringae pv. glycinea. The acetyl content of the P. syringae pv. glycinea alginates varied from 3 to 14%, and the amount of guluronic acid varied from less than 1 to 20%. The P. syringae pv. glycinea alginates from in vitro batch cultures were of lower molecular weight and polydispersity than those from in planta cultures, and both were of lower molecular weights than alginates produced by Pseudomonas aeruginosa.