An extracellular polysaccharide was isolated from the culture mediumofa virulent strain (U-7) of Pseudomonassolanacearum. The polysaccharide caused tomato cuttings to wilt. It seemed to be composed mainly of N-acetylgalactosamine together with small amounts of rhamnose, glucose, and protein. This is, to our knowledge, the first example of homo-N-acetylgalactosaminoglycan in Packard 3380A digital integrator. GC-MS(70eV) were generated with a Hitachi M-80 mass spectrometer and M-003 data processor. The total sugar content was assayed by the phenol-sulfuric acid method.6) Hexosamine was measured colorimetrically7) after hydrolysis in hydrochloric acid. Sugar was analyzed by GLCof the alditol acetates on a Hewlett-Packard fused-silica capillary column (50 mx0.31 mm).8) The 13C-NMR (125 MHz) spectra for solution of EPS in D2Owere recorded on a Brucker AM-500 spectrometer at 30°C using a 5-mmtube and internal methanol (49.9ppm from Me4Si) as the standard. The infrared (IR) spectrum was obtained using a Nicolet 60SX. Total nitrogen was assayed by elemental analysis. Acetic acid was measured with GLC9) using propionic acid as the internal standard. The GLCconditions were as follows: column, a glass column (100 x 0.3cm) packed with Porapack QS (80~100mesh); carrier gas, N2 at 60ml/min; injection temperature, 250°C; oven temperature, 150°C isothermal. Amino acids were analyzed in a JEOL JLC-6AH amino acid analyzer after hydrolysis of the sample in 6n hydrochloric acid at 110°C for 18hr in a sealed glass

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The extracellular polysaccharides produced by 17 virulent strains of Pseudomonas solanacea rum collected from Japan and USA were compared in terms of wilt-inducing activity on tomato cuttings, sugar compositions, amino sugar content and degree of N-acetylation of the amino sugar. It was found that all polysaccharides investigated had wilt-inducing activity on tomato cuttings and that they were composed mainly of N-acetylgalactosamine residue.