 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.The acidophilic archaea "Sulfolobus metallicus" and "Metallosphaera sedula" can tolerate up to 4% of copper and have been exploited for mineral biomining.