The Cultivation of a Single Strain of Actinomyces israelii in a Simplified and Chemically Defined Medium

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Abstract
SUMMARY: Growth curves were determined for a single strain of Actinomyces israelii grown in systematic modifications of the partially defined medium of Howell & Pine (1956). These determinations resulted in a progressive simplification of the Howell & Pine medium and in the elucidation of a completely defined medium containing 335 μg. total-N/ml. instead of 948 μg. total-N/ml. in the original medium; the yield of organism was increased concomitantly from 55 μg. total-N/ml. of medium to 80 μg. total-N/ml. of medium. This simplified medium contained no ammonium sulphate, purine or pyrimidine bases but twenty amino acids (of which L-cysteine and L-tryptophan were found to be essential) and sixteen growth factors.