General Organization of Rhizobium phaseoli nif Plasmids

In R. phaseoli, as in many other rhizobia, sequences homologous to Klebsiella pneumoniae nif genes are plasmid located. In R. meliloti, R. trifolii, and R. leguminosarum, sym plasmids have been identified whose genes are directly involved in nodulation and N2-fixation. We report on the symbiotic and physical properties of R. phaseoli plasmids that contain nif genes.