Presence of sulfide minerals in flotation tailings poses an environmental threat due to enhanced acid formation and heavy metal ion dissolution. 'Acidithiobacillus', group of microorganisms, play a significant role in acid generation from sulfide-bearing tailings through microbial oxidation of associated pyrite and other sulfide minerals. Removal of sulfide minerals from abandoned tailing dams holds the key for environmental protection. In this paper, the role of some Acidithiobacillus group of bacteria such as Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans in the removal of pyrite, chalcopyrite and sulfur from tailing substrates such as quartz is discussed. Surface chemistry of the above microorganisms is illustrated with respect to interaction with pyrite, chalcopytite, sulfur and quartz. Dispersion and flocculation behavior of the above minerals before and after interaction with the above microorganisms was studied. Surface hydrophobicity and hydrophilicity of the above minerals were also assessed with respect to selective flocculation. Separation of sulfides from quartz through selective flocculation/dispersion was achieved through prior biotreatment. (C) 2003 Elsevier B.V. All rights reserved.