SULFUR CHEMISTRY, BIOFILM, AND THE (IN)DIRECT ATTACK MECHANISM - A CRITICAL-EVALUATION OF BACTERIAL LEACHING

It has been shown(a) that bacterial leaching of metal sulfides apparen tly requires the attachment of leach bacteria to metal sulfides, (b) t hat exopolymer-bound iron compounds are responsible for or at least co nsiderably increase the rate of the biological attack over the chemica l rate, (c) that the primary attacking agent in leaching environments is the ferric iron hexahydrate ion, (c) that thiosulfate is the first intermediate sulfur compound, giving rise to a variety of other compou nds including polythionate-containing periplasmic granula, and (d) tha t we have no idea about the actual concentrations of protons, ferrous/ ferric and/or other cations, and sulfur compounds in the reaction spac e between the bacterium and the sulfide surface.