Environments in which extremely acidophilic microorganisms are found occur in many places on Earth. Some are formed naturally while others are the result of human activity. Acidic environments formed outside of human intervention are typically areas with volcanic activity. Inorganic sulfur compounds are brought to the surface where they are oxidized to sulfuric acid. Sulfide-containing minerals may also be exposed or brought to the surface as a result of mining activity and when oxidized these minerals give rise to acid and metal pollution known as acid mine drainage. Biological oxidation of...