GLUTAMINE-SYNTHETASE-II CONSTITUTES A NOVEL TAXONOMIC MARKER IN RHIZOBIUM-ETLI AND OTHER RHIZOBIUM SPECIES

Different Rhizobium species may be identified by using polymorphisms i n their glutamine synthetases (GSII) but not by their GSI profiles. We analyzed the GSs of various Rhizobium tropici and Rhizobium etli stra ins (which are capable of nodulating and fixing nitrogen in Phaseolus vulgaris beans), as well as strains of other species included for comp arison. The GS polymorphisms were determined by identifying variations in native enzyme mobility (revealed by GS activity staining) and in t he isoelectric points of the monomers (revealed by immunodetection wit h antibodies against the GS proteins) by using gel electrophoresis. Re striction fragment length polymorphism patterns obtained by hybridizin g an internal fragment of the GSII gene obtained from R. etli with tot al fragmented DNAs from different strains clearly distinguished the di fferent groups. GSII is a novel and useful marker for Rhizobium groups and species, and GSII data support R. tropici and R. etli as bona fid e species.