COENZYME R REQUIREMENTS OF RHIZOBIA

Abstract

19 strains of Rhizobium trifolii, Rh. meliloti, Rh. leguminosarum, and Rh. phaseoli were found to require addition of coenzyme R to the culture medium in order to make an appreciable growth. The exps. show that: (a) iron salts did not act as a substitute for the essential growth substance, (b) the reducing substances, cysteine and thioglycollic acid, had very little effect on the growth of rhizobia either in the presence or in the absence of the growth substance, (c) the need for coenzyme R was independent of the N source used, and (d) the total growth over a considerable range of concs. of coenzyme R was nearly proportional to the quantity added. These investigations are in agreement with our previous results and in disagreement with the more recent work of Thome and Walker. The chemical nature of coenzyme R has not been determined but it is an organic compound, synthesized by many organisms.