Metal reduction by sulphate-reducing bacteria: physiological diversity andmetal specificity

The reduction of Tc(VII), Cr(VI) Se(IV) and Te(IV) by representatives of th ree genera of sulphate-reducing bacteria was studied with respect to the sp ecificity of electron donor and acceptor. Tc(VII) and Cr(VI) were reduced b y different mechanisms involving a hydrogenase. Cr(VI) reduction was achiev ed using a new isolate with lactate as the electron donor or by using H-2 i n the presence of bicarbonate ion. Te(IV) and Se(IV) were reduced to base m etals. The removal of Se(TV) was enhanced under sulphidogenic conditions, w ith 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.