Polysaccharide production and the possible occurrence of GDP-D-mannose dehydrogenase in Azotobacter vinelandii

During the growth of Azotobacter vinelandii in batch culture in Burk's 2% glucose medium supplemented with 50 mg EDTA per litre, water-insoluble capsular polysaccaride material accumulated in cultures prior to the appearance of water-soluble polysaccharide in the culture medium. On isolation, hydrolysis and chromatography, both these polysaccharides were observed to be composed of carbohydrate monomers having the same chromatographic mobilities as glucose, rhamnos, guluronic acid and mannuronic acid. The activity of GDP-D-mannose dehydrogenase recorded in crude cell-free extracts from Azotobacter vinelandii, when these polysaccharides were produced, may indicate a close similarity between the biosynthetic pathway of alginate synthesis in marine Phaeophyceae and this soil microorganism.