Structures of the oligosaccharides obtained from the core regions of the lipopolysaccharides of Bradyrhizobium japonicum 61A101c and its symbiotically defective lipopolysaccharide mutant, JS314

Abstract

The only core oligosaccharide released from the lipopolysaccharide (LPS) of Bradyrhizobium japonicum 61A101c by prolonged (5 h) mild hydrolysis with acid, and the major core oligosaccharide obtained from its symbiotic and LPS-defective mutant, JS314, was the trisaccharide alpha-D-Man p-(1----4)-alpha-D-Glc p-(1----4)-2,7-anhydro-alpha-Kdof. The 2,7-anhydro-3-deoxy-alpha-D-manno-2- octulofuranosonic acid moiety was probably formed during the prolonged mild hydrolysis with acid. A disaccharide core component, also released by mild acid hydrolysis of the mutant LPS, had the structure 4-O-Me-alpha-D-Man p-(1----5)-Kdo. The Kdo residue in this disaccharide is present as the normal pyranose form and as an anhydro derivative, possibly 4,8-anhydro-3-deoxy-D-manno-2-octulosonic acid, which may have formed also during prolonged mild hydrolysis with acid. Mild acid hydrolysis of the LPS of the parent strain does not produce this disaccharide, but 4-O-Me-Man is found exclusively in the O-chain fraction released from the parent LPS. Additionally, a small amount of O-chain is found in the mutant LPS. The results imply that the O-chain is attached to the remainder of the LPS through the 4-O-Me-Man-Kdo disaccharide component of the core region.