The influence of several metallic ions on Sulfolobus BC activity was examined. The maximum tolerance to increasing quantities of metal in cultures grown on copper concentrate was determined after a period of progressive adaptation. In addition, the influence of several metal concentrations on the capacity of the microorganisms to oxidize ferrous iron and sulphur was studied individually. In all cases silver, mercury, ruthenium and molybdenum inhibited bacterial growth. The use of adapted microorganisms led to an increase in the oxidation rate of both substrates, which was related to bacterial activity.