Xyloglucanase production by rhizobial species

Xyloglucanase activity was evaluated in wild-type strains from different taxonomic groups of rhizobia that nodulate a specific range of legume hosts (Sinorhizobium meliloti, Rhizobium leguminosarum bv.viceae, R. leguminosarum bv.trifolii, R. tropics, Sinorhizobium NGR, Mesorhizobium ciceri, M. mediterraneum).To detect endo-and exoxyloglucanase activities we used viscometric assay and quantitation of reducing groups released with a bicinchoninate reagent respectively.Endoxyloglucanase enzymes were detected in all the rhizobia tested both in the extracellular culture medium and in the intracellular fractions.Exoxyloglucanase activity was only found in the intracellular fraction of the rhizobia strains.These findings are consistent with the hypothesis of an involvement of rhizobial hydrolytic enzymes in the invasion of legume by Rhizobium.