Host-Symbiont Interactions

Abstract

The lipopolysaccharides of 3 strains each of R. leguminosarum, R. phaseoli and R. trifolii were purified and partially characterized. The last step in the purification procedure is gel filtration column chromatography using Sepharose 4B with an elution buffer consisting of EDTA and triethylamine. Each of the lipopolysaccharides reported in this paper elutes as a symmetrical peak in the partially included volume of this Sepharose 4B column. The ratio of 2-keto-3-deoxyoctonate acid (a sugar which is characteristic of lipopolysaccharides) to hexose is constant throughout the carbohydrate-containing peaks as they elute from the Sepharose 4B. The compositions and immunodominant structures of the purified lipopolysaccharides vary as much among strains of a single Rhizobium sp. as among the different species of Rhizobium. There is no obvious correlation between the nodulation group to which a Rhizobium belongs and the chemical composition or immunochemistry of the Rhizobium''s lipopolysaccharide. There is extensive cross-lysis by phage of strains of R. trifolii, R. phaseoli and R. leguminosarum. This suggests that the receptors for these cross-lysing phage reside either in nonlipopolysaccharide structures or in common structures within the lipopolysaccharide which are not detected by compositional or immunochemical analysis.