Metal reduction by sulfate-reducing bacteria: physiological diversity and metal specificity

The reduction of Tc(VII), Cr(VI) Se(IV) and Te(IV) by representatives of three genera of sulphate-reducing bacteria was studied with respect to the specificity of electron donor and acceptor. Tc(VII) and Cr(VI) were reduced by different mechanisms involving a hydrogenase. Cr(VI) reduction was achieved using a new isolate with lactate as the electron donor or by using H-2 in the presence of bicarbonate ion. Te(IV) and Se(IV) were reduced to base metals. The removal of Se(TV) was enhanced under sulphidogenic conditions, with metal sulphide identified by energy dispersive X-ray microanalysis. The order of preference of the electron accepters was Te(IV) > S(VI) > Se(IV), which is in sharp contrast to that predicted by the redox potentials alone. (C) 2001 Elsevier Science B.V. All rights reserved.