Rhizobium leguminosarum
Rhizobium leguminosarum is a bacterium which lives in a mutualistic symbiotic relationship with legumes, and has the ability to fix free nitrogen from the air. "R. leguminosarum" has been very thoroughly studied—it has been the subject of more than a thousand publications. Morphology. "Rhizobium leguminosarum" is a Gram-negative, motile, rod-shaped, aerobic bacterium. Common biovars. "Rhizobium leguminosarum" biovar "trifolii", and "R. leguminosarum" biovar "viciae" are the most commonly studied biovars of "R. leguminosarum", with certain studies seemingly treating "R. trifolii" as its own species. Fatty acid synthesis. "Rhizobium leguminosarum"s acyl carrier protein differs from most ACPs  by having a C-terminus extension. This ACP is also used in the synthesis of unusually long ACPs which themselves are then used in the synthesis of the "R. leguminosarum" nod factor. Uses. "R. leguminosarum" is widely used in the inoculation of legume seeds. The sv. trifolii strain U204 is commercially used to inoculate white and red clover in particular, but better strains for this purpose are being developed. Research has been carried out into the role that "R. leguminosarum" could play in promoting growth of canola and lettuce.