Abstract
Conclusions
1. Approximately one third of a group of representative Group A streptococci required a factor for growth in a semisynthetic medium reinforced with serum which was present in rabbit, human, pig, dog and sheep sera. This factor was absent from horse, cow, rat and mouse sera. 2. The factor could be replaced by yeast nucleic acid and certain of its derivatives, such as xanthine, guanine and hypoxanthine. It could not be replaced by certain other derivatives such as adenine and uracil. 3. Desoxyribonucleic acid was inactive as the factor, but became active after depolymerization by desoxyribonuclease. 4. The lack of uniformity of Group A streptococci with respect to depandence on this factor shows that nutritional studies performed on a single strain cannot be regarded as representative of the entire group.
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