The development of industrial mineral processing using microorganisms has been established now in several countries including South Africa, Brazil and Australia. Iron-and sulfur-oxidizing microorganisms are used to release copper, gold and uranium from minerals. Electrons are pulled off of sulfur metal through oxidation and then put onto iron, producing reducing equivalents in the cell in the process. This is shown in this figure. These reducing equivalents then go on to produce adenosine triphosphate in the cell through the electron transport chain. Most industrial plants for biooxidation of gold-bearing concentrates have been operated at 40 °C with mixed cultures of mesophilic bacteria of the genera "Acidithiobacillus" or "Leptospirillum ferrooxidans". In other studies the iron-reducing archaea "Pyrococcus furiosus" were shown to produce hydrogen gas which can then be used as fuel. Using Bacteria such as Acidithiobacillus ferrooxidans to leach copper from mine tailings has improved recovery rates and reduced operating costs. Moreover, it permits extraction from low grade ores - an important consideration in the face of the depletion of high grade ores.