EFFECT OF PH ON SULFITE OXIDATION BY THIOBACILLUS THIOOXIDANS CELLS WITH SULFUROUS ACID OR SULFUR-DIOXIDE AS A POSSIBLE SUBSTRATE

The oxidation of sulfite by Thiobacillus thiooxidans was studied at va rious pH values with changing concentrations of potassium sulfite. The optimal pH for sulfite oxidation by cells was a function of sulfite c oncentrations, rising with increasing substrate concentrations, while that by the cell extracts was unaffected. The sulfite oxidation by cel ls was inhibited at high sulfite concentrations, particularly at low p H values. The results from kinetic studies show that the fully protona ted form of sulfite, sulfurous acid or sulfur dioxide, is the form whi ch penetrates the cells for the oxidation.