Bradyrhizobium japonicum USDA 110 (National Rhizobium Germplasm Resource Center, USDA/ARS, Beltsville, MD, USA) was used in all studies. This strain was chosen because it grows well (although slowly) on a defined medium (Cole and Elkan 1973). This medium contains only salts, with ammonium chloride as the N source, MES/HEPES buffer, pH 6·75, and arabinose and gluconate as carbon sources.

Use the citation Cole and Elkan 1973.

Thanks so much! I assume this is the article in Antimicrobial Agents and Chemotherapy. Not sure how I overlooked that reference. It's similar to the medium I use now, except mine includes yeast extract. I'll see how other strains grow in the medium you describe.

Dear Jeffry J. Fuhrmann, The yeast mannitol is the most common media for Rhizobia with nutrient salts. I am sure that the bacteria will grow much better on the undefined media than on the defined media. The biggest distinction of Rhizobium from Bradyrhizobium uses the growth rates on mannitol yeast media I believe. In the last analysis rhizobia bradyrhizobium need to stimulate growth promotion and ideally survive well in to soil to prevent need for continue re inoculation. Beside the supplying of nitrogen the BNF can provide an ability to import soil through carbon sequestration which is often limited by soil nitrogen level. Good luck in your studies.