Using the standard straine of Sh. flexneri 2a and St. aureus, the mechanism of AM inhibition on the c-source oxidation of bacteria are studied and the following results ore obtained. 1. AM inhibition of glucose, lactate or pyruvate oxidation can be restored by addition of Fe(++) or Fe(+++), especialy in th case where Fe(++) or Fe(+++) added to cells before addition of AM. 2. AM does not inhibit so markedly the oxygen uptake of the cells grown on the medium added KCN or NaN(3) and adapted to these inhibitors. From these results, it seems that AM inhibits the enzymatic retions by catching Fe(++) the other metal ions necessary to the enzyme actviities. 3. AM inhibition can not be restored by thionine, and AM does not inhibit catalase and peroxidase reaction.