A genus of nitrogen-fixing bacteria that live as symbionts in the root nodules of leguminous plants. The most studied species are R. meliloti and R. trifoli. The genes involved in host specificity, nodulation, and nitrogen fixation are carried on large plasmids, and restriction maps have been constructed of those regions carrying symbiotically important genes. See Classification, Bacteria, Proteobacteria; Chronology, 1981, Hombrecher et al.; bacteroids, nif genes, plasmid, restriction map, sym-plasmid.
Subjects: Genetics and Genomics — Chemistry.