Structural studies of the antigenic polysaccharide of Eubacterium saburreum, strain T19.

The antigenic polysaccharide produced by Eubacterium saburreum, strain T19, contains unusual sugars, including D-glycero-D-galacto-heptose (Hep) and D-fucose (D-Fuc). A repeating unit of the polysaccharide is composed of a linear chain of D-glycero-D-galacto-heptopyranosyl tetrasaccharide as its backbone structure, i.e., -[-->6)-beta-Hep p-(1-->3)-beta-Hep p-(1-]2-->, and a D-fucofuranosyl disaccharide as a branched group, i.e., alpha-D-Fuc f-(1-->2)-alpha-D-Fuc f-(1-->, which is linked to O-4 of one (1--6)-linked D-glycero-D-galacto-heptopyranosyl residue. The polysaccharide also contains O-acetyl groups.