Iron Oxidizing Medium (Twin pack)

Principle And Interpretation

Thiobacillus ferrooxidans is recognized as being responsible for the oxidation of iron and inorganic sulfur compounds in areas such a mine tailings and coal deposits where these compounds are abundant (4,7). The main importance of T. ferrooxidans has been in acid mine drainage. T. ferrooxidans is generally assumed to be obligately aerobic, but under anaerobic conditions, T. ferrooxidans can be grown on elemental sulfur using ferric iron as an electron acceptor. These results indicate that T. ferrooxidans can be considered as facultative anaerobe playing an important role in the iron and sulfur cycles in acidic environments. The ability of this organism to grow in oxygen-deficient environments may have important implications in bioleaching processes where anaerobic conditions may often exist (5). Iron Oxidizing Medium (Thiobacillus ferroxidans) is formulated in accordance with APHA (1) and is used for isolation, cultivation and enrichment of T. ferroxidans. Magnesium sulphate, ammonium sulphate, potassium chloride and calcium nitrate are sources of ions that stimulate metabolism. Dipotassium phosphate buffers the medium. The medium has a precipitate, is opalescent and green in colour. T. ferroxidans utilizes ferrous sulphate as energy source. Some oxidation of iron occurs during sterilization. T. ferroxidans can be enumerated by MPN technique (6). Growth of the organism is manifested by a decrease in pH and an increase in concentration of oxidized iron. With the use of uninoculated controls, an increase of deep orange brown colour can be seen in positive enrichment tubes or flasks as compared to negative ones.