Kazutami Imai

ON THE MECHANISM OF BACTERIAL LEACHING

Manganese dioxide is not soluble in sulfuric acid, but it is solubilized in the growing culture of Thiobacillus thiooxidans. The leaching mechanism is postulated that manganese dioxide is firstly reduced with hydrogen sulfide or sulfite which is formed as an intermediate during the oxidation of sulfur to sulfuric acid by the bacterium, and then solubilized with sulfuric acid. Intact cells or cell-free extracts of T. ferrooxidans are able to oxidize chalcocite in the absence of iron. It suggests the existence of direct oxidizing mechanism, and the mechanism has been investigated. The rate of covellite-leaching in the growing culture of T. ferrooxidans is enhanced by a pre-treatment (shaking in water for 10 days at 30°C) of the covellite. The phenomenon is also observed in the leaching experiments using cells of the bacterium suspended in iron-free 9K medium.

Physiological Studies on Thiobacilli:Part II. The Metabolism of Colloidal Sulfur by the Cell-free Enzyme System of Thiobacillus thiooxidans

Elemental sulfur was metabolized in the colloidal state by cell-free extracts of T. thiooxidans. The activity was found in the soluble fraction (in the supernatant of centrifugation at 130,000 × g for 1 hr). The reaction products were sulfide and thiosulfate. p-Chloromercuribenzoate, acetate monoiodide and potassium cyanide inhibited the reaction.

Physiological Studies on Thiobacilli: Part IV. Purification and Certain Properties of Cytochrome c from Thiobacillus thiooxidansPart V Extraction of NADPH-Cytochrome c Oxidoreductase from Thiobacillus thiooxidans

The electrophoretically pure preparation of cytochrome c from Thiobacillus thiooxidans was obtained. The absorption spectrum exhibited maxima at 415, 521 and 550 mμ in reduced form. The various properties of the cytochrome were very close to these of mammalian cytochrome c, i. e., absorption spectrum, electrophoretic pattern, isoelectric point and E0′.Electrophoretically homogenous preparation of NADPH-cytochrome c oxidoreductase was isolated from the soluble fraction of Thiobacillus thiooxidans. The purification of the enzyme was carried out using the fractionation with ammonium sulfate, the treatment with Amberlite IRC-50 and the disk electrophoresis.