This study is carried out to determine the mechanism of mutual action between two substrates which act to accelerate bacterial respiration by their mutual action. From the results of some experiments with some strains of B. dysenteriae, such as Sh. dysenteri 3, Sh. flexneri 1. Sh. flexneri 3, two types of mechanism of the action was discovered, they are as follows. (1) In the case of succinate and aspartate, or succinate and glutamate, these combinations of substrates can accelerate the respiration as compared in the case of each substrate alone. The mechanism of this mutual action included aspartate ⇋ glutamate reaction. (2) In the case of couples in which one substrate is glucose, pyruvate, or succinate and another is tartarate, citrate, histidine, tryptophane, tyrosine, or lysine, these couples of substrates can acceletate the respiration too, in spite of the fact that the latter substrates cannot be oxidized when they are added alone to organisms. The mechanism of this mutual action includes the phosphorous metabolism coupling with oxidation, and addition of the substrates such as tartrate, citrate, etc. to glucose, pyruvate, etc. seemed to activate ATP ⇋ ADP reaction.