Diversity of Acidophilic Bacteria and Archaea and their Roles in Bioremediation of Acid Mine Drainage

Aims: To show the potential of acidophilic bacteria and archaea in bioremediation of acid mine drainage.
The Mining industry generates wealth, but its long term adverse effects, which include acid mine drainage (AMD), cannot be overlooked. Acid mine drainage occurs as a result of biological and chemical oxidation of sulphide containing minerals with consequent production of acidic metal rich effluents. AMD is a serious environmental pollution problem in both active and abandoned mines worldwide, resulting in continual contamination of surface and groundwater resources with heavy metals. Acidophilic bacteria and archaea have been known to contribute to the accentuation of this problem by speeding up the reaction time for biological oxidation of sulphide containing mineral waste rock. The dominant metal present in AMD is iron with high sulphate content; the iron may be present in either ferrous or ferric form or both depending on the water pH. Reduction of these two important constituents by generating alkalinity through chemical or biological means has been reported to have a significant effect in AMD impacted water. The metabolic activities of the acidophilic bacteria and archaea through ferric iron and sulphate reduction, a natural attenuation process, also help in remediating this pollution problem by generating alkalinity that immobilizes metals thereby reversing the reactions responsible for the genesis of AMD. This article reviews the various groups of the acidophilic prokaryotic microorganisms and their metabolic activities that help in remediating the problem of AMD in gold mines.