Production and Chemical Composition of Extracellular Polysaccharides of Rhizobium

Abstract

Five cultures of Rhizobium meliloti (J7017, 202, 204, 207, 209) and one of Rhizobium trifolii (J60) produced water-soluble polysaccharides containing glucose, galactose and pyruvic acid in a molar ratio of 7:1:1 and some succinic and acetic acids. These were identified as succinoglycan-like polysaccharides on the basis of their components, methylation analysis and fragmentation with two specific β-glycanases. One culture of R. meliloti (IFO 13336) produced water-soluble polysaccharide containing glucose, galactose, glucuronic acid and acetic acid in a molar ratio of 5:1:1:2, and an unidentified component. Two cultures of R. meliloti (201, 206) produced water-soluble polysaccharides containing glucose, galactose, mannose and glucuronic acid in a molar ratio of 4:2:3:1 and 4:1:2:1, respectively, and some pyruvic acid. Rhizobium trifolii IFO 13337 and R. japonicum IFO 13338 produced water-soluble polysaccharides containing glucose, galactose, glucuronic acid, pyruvic acid and acetic acid in a molar ratio of 6:1:1:2:1. Two isolates from the stock culture of R. trifolii J60 produced large amounts of the water-insoluble polysaccharide curdlan. This is the first report in Rhizobium of the occurrence of curdlan and of spontaneous mutation in ability to produce succinoglycan-like polysaccharide and curdlan.