Abstract
The synthetic medium for Shigella dysenteriae which has hitherto been known contains many amino acids and also niacin-amide, although the necessity of which remains obscure (5, 11, 12) . We have been examining the process of the evolution of the bacterial nutrition (or the retroevolution), especially about the nitrogen source. It is the purpose of this paper to report the nutritional nitrogen source for Shigella dysenteriae and also the significance of niacin-amide in its synthetic medium.
The strain used in this experiment is Shigella dysenteriae (Shiga type, Hanabusa) kept in N. I. H. of Japan. In the beginning Shigella dysenteriae was cultivated in the chemically defined medium as similar as possible to that of Dorfman et al (5) . One by of a amino acids were eliminated, until the minimum requirement of nitrogen source was determined as glutamic acid. Further experiments were designed to test the dispensability of niacin-amide along the growth curve in this medium. Since niacin-amide was not found always indispensable in this case, the content of niacin-amide-like substance was examined quantitatively.
