Synthesis of Growth Factors by Rhizobium trifolii

Abstract

A STUDY of the growth factor requirements of Rhizobium trifolii has indicated that, under suitable conditions, the organisms are able to synthesize all the organic substances essential for growth from a synthetic carbohydrate - mineral salts medium of known composition. Although various extracts of plants and micro-organisms contain a heat-stable factor stimulative to growth, it is not required for successful continuous transfer of the organism in synthetic media. A base medium, claimed by Allison and Hoover¹ to be incapable of supporting continued growth of the nodule organism in the absence of extracts of Azotobacter or other substances (termed ‘coenzyme R â), was found to be satisfactory after adjusting the oxidation-reduction potential and adding iron. Although the growth was not profuse in comparison with media which contain plant extracts, continuous transfer was possible.