R. leguminosarum was split into two biovars viciae and trifolii . Further studies showed that there was greater diversity among R. leguminosarum strains than any other bacterial species. The full taxonomic relationships have not yet been established. Acid production from glucose is common but some produce alkali. Many strains can denitrify.
All strains can grow on many mono and disaccharides.
Phages have been obtained from soil and varying susceptibilities to them have been used to characterise strains. DNA-DNA hybridization studies have also been used to establish strain relationships. Both bacterial preparations from root-nodules as well as pure cultures can be used as antigens. Both agglutination and fluorescent antibody studies have been successfully used. There is a great deal of antigenic heterogeneity among strains of Rhizobium .