THE NATURE OF SOME GROWTH STIMULATORY SUBSTANCES FOR LACTOBACILLUS DELBRUECKII

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Abstract
Addition of crude natural materials such as yeast and liver fractions to a defined medium reduces considerably the time required for heavy growth from small inocula of L. delbrueckii. Tests on more purified preparations revealed at least two categories of growth stimulatory factors: degradation products of ribonucleic acid, and peptides resulting from the enzymatic hydrolysis of proteins. Of known compounds tested, uridylic and cytidylic acids were most active in promoting rapid growth while uridine and cytidine were less active. Adenosine and guanosine had slight activity while adenylic and guanylic acids were inactive.