RESUMO
A study was conducted on the structure of extracellular, water-soluble polysaccharides from 5 different strains of Rhizobium viz. R. trifolii J60 and R. meliloti strains J7017, 202, 204 and 207. All these polysaccharides were found to contain glucose and galactose in the approximate molar ratio of 7:1. Methylation analysis revealed these polysaccharides to contain (1 → 3), (1 → 6), (1 → 4), (1 → 4, 1 → 6)-linked D-glucose residues, (1 → 3)-linked D-galactose and nonreducing terminal D-glucose attached to pyruvate. These polysaccharides were also found to be acylated by both acetyl and succinyl residue. This structure was found to be similar to that of succinoglycan, a succinic acid-containing water-soluble, extra-cellular polysaccharide elaborated by Alcaligenes faecalis var. myxogenes 10C3. This similarity in structure of polysaccharides from two different species of Rhizobium and also the polysaccharide produced by Alcaligenes has been discussed.