Reactive Oxygen Species Influence Biofilm Formation of Acidophilic Mineral-Oxidizing Bacteria on Pyrite

摘要

Reactive oxygen species (ROS), such as hydrogen peroxide (H_2O_2), superoxide ((O_2)~-) and hydroxyl radicals (OH) are known to be formed on the surface of metal sulfides in aqueous solution under oxic and anoxic conditions. Consequently bacteria which have not been adapted to their presence are metabolically inhibited [1], presumably due to the presence of these ROS. Pyritegrown cells of Acidithiobacillus ferrooxidansT, in contrast to iron(II)-grown cells, were able to oxidize iron(II)-ions or pyrite after 24 h starvation and contact with 1 mM externally added H_2O_2. In this study, similar results were obtained with Acidiferrobacter sp. SPIII/3. However, Acidithiobacillus ferrivorans SS3 showed the highest tolerance towards contact with H_2O_2, while Leptospirillum ferrooxidans DSM 2391 was most sensitive. Similar results were obtained after exposure to defined doses of gamma radiation, which cleaves water molecules and generates ROS. In this study members of the three aforementioned genera of mineral-oxidizing bacteria were compared regarding their ability to survive, colonize pyrite and to oxidize iron(II)-ions after exposure to different concentrations of H_2O_2. Pyrite colonization was studied after exposure to endogenous ROS formed on pyrite or after external addition of H_2O_2 using confocal laser scanning microscopy (CLSM).