Characterization of structural defects in the lipopolysaccharides of symbiotically impaired Rhizobium leguminosarum biovar viciae VF-39 mutants.

The lipopolysaccharides (LPS) of a wild type strain of Rhizobium leguminosarum biovar viciae (strain VF-39) and two symbiotically defective Tn5 mutants (VF-39-32 and VF-39-86) have been studied. The LPS of the mutants reflected impaired synthesis of the O-antigen. In the LPS of one mutant, the core tetrasaccharide was lacking and in that of the other it was truncated to a disaccharide containing mannose and 3-deoxy-D-manno-oct-2-ulosonic acid (KdO). The latter mutant also synthesized an unusual carbohydrate component containing mannose, galactose, and an unidentified saccharide. The lipid A composition was similar to that found in other strains of R. leguminosarum biovar viciae. The O-antigen of the wild-type bacterium contained 2-O-methylfucose, fucose, 3,6-dideoxy-3-(methylamino)hexose, glucose, 2-amino-2,6-dideoxyhexose, and heptose. This study clearly defines a role for the bacterial LPS in the proper functioning of the Rhizobium legume symbiosis.