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Abstract
The structure of an extracellular acidic polysaccharide (APS-I) of R. meliloti 201 was studied. Digestion of APS-I with APS-I depolymerase revealed that it consists of three repeating units of oligosaccharides, termed OP1, OP2 and OP3, in a ratio of 55 :25:20 (by weight). 1H-NMR analysis, methylation analysis, Smith degradation and α-D-mannosidase digestion indicated that OP1 was a pentasaccharide with the following structure:
The structures of OP2 and OP3 were not fully elucidated, but each oligosaccharide had some structural similarities with OP1, containing a (1→4)-linked d-glucuronosyl residue, (1→3)(1→4)-linked d-mannosyl residue, (1→3)-linked reducing-terminal d-glucose residue and non-reducing-terminal d-mannosyl and d-glucosyl residues.