Structural studies on the core oligosaccharide of Phenylobacterium immobile strain K2 lipopolysaccharide. Chemical synthesis of 3-hydroxy-5c-dodecenoic acid.

The fatty acid composition of the bound lipids of 17 strains from Phenylobacterium immobile was investigated. Ester-linked 3-hydroxy-5c-dodecenoic acid was found to be the major substituent in the lipopolysaccharide. Therefore the occurrence of this unusual acid can be taken as a useful marker for the determination of P. immobile by simple fatty acid analysis. Lipid A backbone was found to consist of 2,3-diamino-2,3-dideoxy-D-glucose, which up to this time has only been detected in group I of purple nonsulfur bacteria and their non-phototrophic relatives. A convenient chemical synthesis for 3-hydroxy-5c-dodecenoic acid is described. The polysaccharide region of P. immobile strain K2 lipopolysaccharide was investigated. The methods used included gel filtration procedures, methylation analysis, periodate oxidation, Smith degradation, oxidation with chromium trioxide and enzymic degradations of the isolated oligosaccharide. We found that strain K2 has a rough-type lipopolysaccharide, devoid of an O-specific side chain. For the core oligosaccharide the following structure is proposed: (Formula: see text) beta-D-Glcp(1-3)-L-alpha-D-Hep rho(1-3)-L-alpha-D-Hep rho(1-3-L-alpha-D-Hep rho(1-4/5)dOclA.