The structures of the lipopolysaccharide core components from Rhizobium leguminosarum biovar phaseoli CE3 and two of its symbiotic mutants, CE109 and CE309

Abstract

The structures for the core regions of the lipopolysaccharides (LPSs) from R. leguminosarum bv. phaseoli CE3 and two symbiotic mutants were determined by g.l.c.-m.s., proton nuclear magnetic resonance spectroscopy (n.m.r.), fast-atom-bombardment mass spectrometry (f.a.b.-m.s.), and by comparison with known structures from the LPS of R. leguminosarum bv. trifolii ANU843. The core oligosaccharides were separated into two components, P2-2 and P2-3, by gel-filtration chromatography using Bio-Gel P2. The P2-2 oligosaccharide from CE3 is a tetrasaccharide consisting of 3-deoxy-D-manno-2-octulosonic acid (Kdo), mannose, galactose and galacturonic acid. The mannosyl residue is alpha-linked to O-4 of Kdo, and the galactosyl and galactosyluronic residues are alpha-linked to O-4 and O-6, respectively, of the mannosyl residue. The P2-2 oligosaccharide from mutant CE109 is missing the galactosyluronic residue, while that from mutant CE309 is missing both the galactosyl and galactosyluronic residues. The P2-3 oligosaccharide from CE3 LPS is a trisaccharide consisting of two galactosyluronic residues alpha-linked to the O-4 and O-7 of Kdo. Fraction P2-3 from mutant CE309 has the same structure as CE3 P2-3. Fraction P2-3 from mutant CE109 contains galacturonic acid and Kdo, but its structure differs from that of CE3 P2-3.