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Rhizobia are from the Family Rhizobiaceae, which contains several genera: Azorhizobium , Bradyrhizobium , Mesorhizobium , Rhizobium , and Sinorhizobium . Genetic studies place them among the proteobacteria, in an order called the Rhizobiales which is likely monophyletic. However, that group also includes a number of other bacteria, and the rhizobia appear scattered among them. For example, Sinorhizobium meliloti, which nodulates alfalfa, is more related to the plant pathogen Agrobacterium than to the rhizobia that nodulates soybeanSoybeans ( US) or soya beans ( UK) Glycine max are a high- protein legume (Family Fabaceae) grown as food for both humans and livestock. The word soy comes from Japanese shoyu. Soybeans may be boiled whole (in the green pod) and served with salt, often un. Their symbiotic geneDNA and to a chromosome (right). Introns are regions often found in eukaryote genes which are removed in the splicing process: only the exons encode the protein. This diagram labels a region of only 40 or so bases as a gene. In reality many genes are muchs may be much more closely related, however, and acquired by horizontal transferHorizontal gene transfer is any process in which an organism transfers genetic material (i. DNA) to another cell that is not its offspring. By contrast, vertical transfer occurs when an organism receives genetic material from its ancestor, e. its parent o rather than from a common ancestorA group of organisms is said to have common descent if they have a common ancestor. In biology, the theory of universal common descent proposes that all organisms on Earth are descended from a common ancestor or ancestral gene pool. A theory of universal.

The legume-rhizobium symbiosisClownfish (Amphiprion ocellaris) in their Magnificent Sea Anemone (Heteractis magnifica) home. Symbiosis (pl. symbioses) is an interaction between two organisms living together in more or less intimate association or even the merging of two dissimilar org is a classic example of mutualismIn biology, mutualism is an interaction between two species in which both organisms derive some degree of benefit. Mutualism can involve brief or long-term interactions (pollination versus lichen symbiosis between fungus and alga) and may or may not be ob, but its evolutionary persistence is actually somewhat surprising. Because several unrelated strains infect each individual plant, any one strain could redirect resources from nitrogen fixation to its own reproduction without killing the host plant upon which they all depend. But this form of cheating should be equally tempting for all strains, a classic tragedy of the commons. It turns out that legume plants guide the evolution of rhizobia towards greater mutualism by reducing the oxygen supply to nodules that fix less nitrogen, thereby reducing the frequency of cheaters in the next generation.

Frankia and Azospirillum , are genera of similar bacteria that do not live on legumes.