New glycopolymers containing both D- and L-rhamnopyranoses from Rathayibacter iranicus VKM Ac-1602T cell wall

The cell wall of Rathayibacter iranicus VKM Ac-1602 T (family Microbacteriaceae, class Actinobacteria) is characterised by the absence of phosphate-containing and by the presence of two rhamnose-containing glycopolymers. The first is a branched rhamnomannan, in which 60% of mannose residues of the main chain are glycosylated by terminal mannose residues: →2)-α-D-Rha p -(1 → 3)-α-[α-D-Man p -(1 → 6)]-D-Man p -(1 → . The second is a branched teichuronic acid, in which all the rhamnose residues of the main chain are glycosylated by glucose residues:→3)-α-[α-D-Glc p -(1 → 2)]-L-Rha p -(1 → 4)-β-D-Glc p A-(1 → 2)-α-D-Man p -(1 → 3)-α-D-Gal p -(1 → 3)-β-D-Glc p -(1 → . Both glycopolymers have the unique structures and described in the cell walls of Gram-positive bacteria for the first time. The obtained data allow for a more complete characterisation of the cell wall of the microorganism under investigation and can serve as a phenotypic characterisation of this bacterium. The glycopolymer structures were established using chemical and nuclear magnetic resonance (NMR) spectroscopy methods. • The structures of two branched cell wall rhamnose-containing polymers are identified. • The neutral rhamnomannan contains D-Rha p , D-Man p in the ratio 2:3. • The acidic contains L-Rha p , D-Glc p A, D-Man p , D-Gal p, D-Glc p in the ratio 1:1:1:1:2.