Nod Metabolites and Other Compounds Excreted by Rhizobium Sp.

The formation of a nitrogen fixing nodule is the result of a successful communication process between plants and bacteria. In response to root exudates or flavonoids, the Rhizobium species produce lipo-oligosaccharides, or Nod factors, that are responsible of eliciting meristems and nodule-like structures in roots. From the discovery of Nod factors in R. meliloti (Lerouge et al., 1990), different research groups have defined the corresponding chemical structures from Nod metabolites produced by different Rhizobium strains (Bec-Ferte et al., 1993; Carlson et al., 1993; Firmin et al., 1993; Lopez-Lara et al., 1995; Mergaert et al., 1993; Price et al., 1992; Sanjuan et al., 1992; Schultze et al., 1992; Spaink et al., 1991).