Mechanism of Growth Inhibition by Tungsten in Acidithiobacinusferrooxidans

served among the 300 strains tested, the mechanism of inhibition by Na2W04 was studied with Aeidithiobacillus flei:rooxidans strain AP19-3. When resting cells of AP19-3 were incubated in O.1 M fi-alanine-SOZbuffer (pH 3.0) with O.1 mM Na2W04 for 1 h, the amount of tungsten bound to the cel)s was 12"glmg protein. The optimum pH for tungsten binding to the resting cells was 2 -3. Approximately 2 times more tungsten bound te the cells at pH 3.0 than at pH 6.0. The tungsten bindillg was specifically inhibited by sodium molybdenum. Howeyer, copper, nickel, cadmium, zinc, manganese, cobalt, and yanadate did not disturb tungsten binding to the resting cells. The iron-oxidizing activity of AP19-3 was inhibited 24, 62, and 77% by 1, 5, and 10 mM of Na2W04, respectiyely. Among the components of iron oxidation enzyme system, iron:cytochrome c oxidere-