Properties of extracellular polysaccharides from Rhizobium

Abstract

Extracellular polysaccharides from Rhizobium were separated into type I, isolated by precipitation with hexadecyltrimethylammonium bromide and type II, obtained by adding potassium hydroxide to the solution when no type I material was present. Total carbohydrate as glucose in the polysaccharides ranged from 21 to 92% and glucuronic acid, from 0 to 22%. Small quantities of nitrogen always remained in the samples after purification. Specific rotation values showed a wide range from −90 to +150°. Reduced specific viscosities ranged from 600 to 66,000 cm 3/g. Paper chromatographic analyses of 14 polysaccharides showed a difference between the types I and II products, particularly in the concentrations of glucose and mannose. Where several cultures within one group were tested, no direct relationships appeared evident between host legume and constituent sugars. Column electrophoretic separation of six poly-saccharides gave glucose (63–86%), galactose (14–20%), mannose (0–13%), and glucuronic acid (0–10%). Characterization results indicated as many differences within a single host legume group as between groups, suggesting that polysaccharide analysis has limited value as a diagnostic tool for classification of the Rhizobium.