With Sh. flexneri 2a, the standard stocked in our laboratory, as the test bacteria, after examining enzymatic properties of bacteria cultured the medium of which Fe⁺⁺ had been reduced by addition of αα'-dipyridyl and also in the medium containing sufficient Fe⁺⁺, and after examining metabolic properties of the bacteria, the author obtained the following results: 1. Irrespective of whichever carbon source is used, the enzymatic activity involved in the complete oxidation of pyruvate in the process of glucose oxidation is markedly lowered when the bacteria are cultured in the medium with reduced Fe⁺⁺. 2. Oxidation pathway from glucose to pyruvat taken by the bacteria cultured in the medium with reduced iron content does not differ from that taken by the bacteria cultured in the medium containing sufficient Fe⁺⁺. 3, Even in the case of the bacteria cultured in the medium with reduced Fe⁺⁺ there occurs no conversion from cytochrome system of the H-transport system to flavine system.