Chemical characterization of pH-dependent structural epitopes of lipopolysaccharides from Rhizobium leguminosarum biovar phaseoli.
Lipopolysaccharide (LPS) was isolated from free-living Rhizobium leguminosarum bv. phaseoli CE3 cells grown at pH 4.8 (antigenically similar to bacteroid LPS) and compared with that from cells grown at pH 7.2 (free-living bacteria). Composition analysis revealed that pH 7.2 LPS differs from pH 4.8 LPS in that 2,3,4-tri-O-methylfucose is replaced by 2,3-di-O-methylfucose. The amount of 2-O-methylrhamnose is greater in the pH 4.8 LPS than in the pH 7.2 LPS. Analysis of the structural components of LPS (O-chain polysaccharide, core oligosaccharides, and the lipid A) revealed that all the composition differences in the various LPSs occur in the O-chain polysaccharide. These structural variations between pH 4.8 and pH 7.2 LPSs provide a chemical basis for the observed lack of cross-reactivity with pH 4.8 LPS of two monoclonal antibodies, JIM28 and JIM29, raised against free-living bacteria grown at pH 7.2. An LPS preparation isolated from bacteroids contained both 2,3,4-tri-O- and 2,3-di-O-methylfucose residues. This result is consistent with the finding that the two monoclonal antibodies react weakly with bacteroid LPS. It is concluded that methylation changes occur on the LPS O-chain of R. leguminosarum bv. phaseoli when the bacteria are grown at low pH and during nodule development.
Complex Carbohydrate Research Center, University of Georgia, Athens 30602.
U R
UR
Bhat
R W
RW
Carlson
D000907:Antibodies, Bacterial / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000276:immunology; D000942:Antigens, Bacterial / Q000737:chemistry*; D002849:Chromatography, Gas; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D000939:Epitopes; D005227:Fatty Acids / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000276:immunology; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D009005:Monosaccharides / Q000032:analysis; D016961:Rhizobium leguminosarum / Q000737:chemistry* / Q000276:immunology
D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D000939:Epitopes; D005227:Fatty Acids; D008070:Lipopolysaccharides; D009005:Monosaccharides