Partial Structure of Lipopolysaccharides Isolated from Rhizobium leguminosarum bv. trifolii 24 and Its GalA-Negative Exo − Mutant AR20

Abstract

Summary Structural studies of two lipopolysaccharides (LPS) isolated from Rhizobium leguminosarum bv.trifolii strain 24 (giving effective symbiosis with clover) and the exo− mutant AR20 showing non-effective nodulation, were performed using conventional techniques (chemical analysis, gas chromatography (GC), methylation analysis, combined gas chromatography/mass spectrometry (GC-MS)) and NMR.The two LPS preparations contained: L-rhamnose, 6-deoxy-L-talose (dTal), D-mannose, D-galactose, D-glucose, 3-deoxy-2-heptulosaric acid (DHA) and 2-keto-3-deoxyoctonate (KDO) as major sugar components, as well as a 2,3-di-O-methylhexose, a 2,6-dideoxy-2-amino-hexose, D-glucosamine and glucosaminic acid as minor constituents.D-galacturonic acid (GalA), however, was found only in the preparation from the wild-type strain 24.All neutral hexoses and 6-deoxyhexoses have been identified as α-linked anomers. The detailed elucidation of two trisaccharide, derived from the exo− mutant AR20, namely α-L-dTalp(l→2)α-L-Rhap(l→5)DHA and α-D-Galp(l→5)α-D-Manp(l→6)KDO by methylation analysis and NMR techniques will be presented.Furthermore, the overall structure of the LPS of the wild-type strain 24 will be proposed