Structural determination of the Nod factors produced by Rhizobium gallicum bv. gallicum R602

Rhizobium gallicum is a fast-growing bacterium found in European, Australian and African soils; it was first isolated in France. It is a microsymbiont which is able to nodulate plants of the genus Phaseolus . Rhizobium gallicum bv. gallicum R602 produces four extracellular signal molecules consisting of a linear backbone of N -acetyl glucosamine, bearing on the nonreducing terminal residue an N -methyl group and different N -acyl substituents. The four acyloligosaccharides terminate with a sulfated N -acetylglucosaminitol. This unit may be also acetylated. These structures were determined using carbohydrate and methylation analysis, mass spectrometric analysis and one-dimensional- and two-dimensional-nuclear magnetic resonance experiments. This work establishes the common structure that a lipochito-oligosaccharide must have so that the Rhizobium that produces and excretes it is able to nodulate plants of Phaseolus vulgaris . The substituents common to all the molecules are an N -methyl group and a C18:1 fatty acid on the nonreducing terminal residue.