STUDIES ON THE LEGUME ROOT NODULE BACTERIA: III. GROWTH FACTOR REQUIREMENTS FOR EFFECTIVE, INEFFECTIVE, AND PARASITIC STRAINS

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Abstract
Under the experimental conditions used, amino acids played a very important part in the growth initiation of washed cells of alfalfa – sweet clover rhizobia. There were, however, distinct differences in utilization, both among genetically related mutants, and among other cultures when compared before and after plant passage. None of 15 vitamins, purines, and pyrimidines was able to initiate growth and hence these rhizobia are able to synthesize these compounds when a readily utilizable nitrogen source is present. Because of this fact, the stimulation of these bacteria by yeast extract is probably due, primarily, to the amino acid content. No strain was found able to concentrate free amino acids intracellularly or, when grown in lysine or tyrosine media, to excrete additional amino acids. No differences were found among effective, ineffective, or parasitic rhizobia in biochemical requirements.

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