W. Sand et al., SULFUR CHEMISTRY, BIOFILM, AND THE (IN)DIRECT ATTACK MECHANISM - A CRITICAL-EVALUATION OF BACTERIAL LEACHING, Applied microbiology and biotechnology, 43(6), 1995, pp. 961-966
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.