Facultative-Thermophilic Thiobacillus-Like Bacteria in Metal Leaching

Thiobacillus-like microbes capable of oxidizing ferrous iron at pH 1.6 and a temperature of 55° have been found in thermal springs (Brock et al., 1976: LeRoux et al., 1977), a large-scale copper leaching test system (Brierley and Lockwood, 1977), commercial dump leaching operations at the Chino Mine, Hurley, New Mexico (Brierley, 1978), the Bingham Canyon Mine, Bingham, Utah, the Vlaidov Vrah Mine, Bulgaria (Groudev et al., 1978), and ore deposits in the USSR (Golovacheva and Karavaiko, 1977). These microbes have a chemolithotrophic heterotroph or mixotrophic mode of metabolism. They oxidize ferrous iron, pyrite or other metallic sulfides for energy, but growth occurs only in media supplemented with a reduced carbon compound such as yeast extract or glutathione. These microbes do not appear to fix carbon dioxide (Brierley et al., 1978) and may not reductively assimilate sulfate (Brierley et al., 1979).