The Exclusion of D 2 O from the Hydration Sphere of FeSO 4 · 7H 2 O Oxidized by Thiobacillus ferrooxidans

Microbial leaching of metals from sulfide minerals

Microorganisms are important in metal recovery from ores, particularly sulfide ores. Copper, zinc, gold, etc. can be recovered from sulfide ores by microbial leaching. Mineral solubilization is achieved both by 'direct (contact) leaching' by bacteria and by 'indirect leaching' by ferric iron (Fe(3+)) that is regenerated from ferrous iron (Fe(2+)) by bacterial oxidation. Thiobacillus ferrooxidans is the most studied organism in microbial leaching, but other iron- or sulfide/sulfur-oxidizing bacteria as well as archaea are potential microbial agents for metal leaching at high temperature or low pH environment. Oxidation of iron or sulfur can be selectively controlled leading to solubilization of desired metals leaving undesired metals (e.g., Fe) behind. Microbial contribution is obvious even in electrochemistry of galvanic interactions between minerals.

Sulfate-dependent iron oxidation by Thiobacillus ferrooxidans: characterization of a new EPR detectable electron transport component on the reducing side of rusticyanin

Iron(II) oxidation by pH 2.5 HCl-washed cells of Thiobacillus ferrooxidans is known to be sulfate dependent. Sulfate dependence of the autooxidation of a novel component in the electron transport pathway is demonstrated. This component exhibits an electron paramagnetic resonance (EPR) signal in the oxidized state at g = 2.005 distinguishable from the g = 2.08 signal attributed to rusticyanin. The novel component is proposed to be a three-iron-sulfur cluster based upon the g value, lineshape, and temperature dependence. Oxyanion specificity for the EPR signal has the same dependence on sulfate as does iron(II) oxidation. By using azide to inhibit electron transfer to oxygen, sulfate was shown to be involved in electron transfer from the g = 2.005 component to the copper of rusticyanin.