The development of industrial mineral processing has been established now in several countries including South Africa, Brazil and Australia. Iron-and sulfur-oxidizing microorganisms are used to release occluded copper, gold and uranium from mineral sulfides. 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 subsequent studies the dissimulatory iron-reducing archaea "Pyrococcus furiosus" and "Pyrobaculum islandicum" were shown to reduce gold chloride to insoluble gold.