Effect of Plasmid pIJ1008 from Rhizobium leguminosarum on Symbiotic Function of Rhizobium meliloti.

Plasmid pIJ1008, which carries determinants for uptake hydrogenase (Hup) activity, was transferred from Rhizobium leguminosarum to Rhizobium meliloti without impairing the capacity of the latter species to form root nodules on alfalfa. The plasmid was still present in rhizobia reisolated from the root nodules of 12 different alfalfa cultivars, but only low levels of Hup activity were detected in alfalfa.