Studies on Cultural Requirements of Bacteria

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Abstract
In continuation of earlier studies in which it was attempted to define the growth requirements of certain pathogenic microorganisms by chemical fraetionation of the complex media ordinarily used for their growth, a strain of diphtheria bacillus has been studied. Starting with the usual peptone-meat infusion broth, the peptone was replaced by tryptophane, plus an amino-acid mixture resulting from an acid hydrolysis of casein. The latter mixture was found to owe its effect to cystine and to an unidentified substance found in the proline fraction made by Dakin''s butyl-alcohol method. Meat infusion may be replaced by Liebig''s meat extract, and from this all basic material, as well as all ether-soluble organic acids, may be removed without greatly altering the amount of growth obtained.