Growth-Stimulating Properties of Cystine and Tryptophan

Abstract

It was reported in a previous study ia that the amino-acid tryptophan was apparently necessary to the growth of certain strains of Clostridium botulinum when the organisms were grown on mediums in which the only source of nitrogen was hydrolyzed casein and the preparations made from such hydrolysates. It was found that a medium prepared of hydrolyzed casein alone would not support growth but that when purified tryptophan was added in proportions sufficient to replace the original tryptophan of the casein, which had been destroyed during the course of acid (H2S04) hydrolysis, growth not only took place but was most profuse. It was later found, in a study lb of the growth of the same strains of bacteria on synthetic mediums, that tryptophan per se was not necessary to growth and that the organisms grew well in the complete absence of this amino-acid.