THE STRUCTURE OF THE EXTRACELLULAR POLYSACCHARIDE OF AZOTOBACTER INDICUM

Abstract

The extracellular polysaccharide of the Azotobacter indicum has been shown to be a mixture of two polymers of which the acidic polymer was a major fraction. The acidic polymer contained D-glycero-D-mannoheptose in the molar ratio of 1:1:1 plus traces of mannose. It consumed 1 mole of sodium metaperiodate per mole of an average anhydroaldose unit and released 0.95 moles of formaldehyde per anhydroheptose unit. Reduction of the oxidized polymer followed by hydrolysis yielded D-glucose, glycerose, glycolaldehyde, and glycerol. Complete fission of the methylated polymer yielded 2,3-di-O-methyl-D-glucuronic acid, 2,4,6,-tri-O-methyl α-D-glucose and 3,4,6,7-tetra-O-methyl D-glycero-D-mannoheptose. Partial hydrolysis of the methylated polymer produced a methylated aldotriouronic acid composed of 1 mole each of 2,3-di-O-methyl-D-glucuronic acid, 2,4,6-tri-O-methyl-D-glucose and 3,4,6,7-tetra-O-methyl D-glycero-D-mannoheptose. A methylated aldobiouronic acid was also produced and was shown to be composed of 2,3-di-O-methyl-D-glucuronic acid and 2,4,6-tri-O-methyl D-glucose.On the basis of these results it is proposed that the polysaccharide is a linear molecule composed of repeating units of D-glucuronic acid, D-glucose, and D-glycero-D-mannoheptose.