Respiratory inhibition of Sphaerotilus by potassium ferrate

Potassium ferrate (K₂FeO₄) is a strong oxidant that might replace chlorine in the disinfection of water. K₂FeO₄ strongly inhibited the respiration of the bacterium Sphaerotilus, which frequently causes filamentous bulking in activated sludge. To identify the mechanism by which K₂FeO₄ caused inhibition, the distribution of iron sorbed by the bacterium was investigated by a modification of the method of Romano and Peloquin. Iron that penetrated into the cells inhibited the endogenous respiration of Sphaerotilus. The inhibition of the dehydrogenase activity of the bacterium by the ferrate was then studied. This enzyme activity was strongly inhibited by K₂FeO₄, but was restored by the addition of 2-mercaptoethanol. Lineweaver-Burk plots showed that K₂FeO₄ was a non-competitive inhibitor of the respiration of Sphaerotilus.