Metal Reduction at Low pH by a Desulfosporosinus species: Implications for the Biological Treatment of Acidic Mine Drainage

Abstract

We isolated an acid-tolerant sulfate-reducing bacterium, GBSRB4.2, from coal mine-derived acidic mine drainage (AMD)-derived sediments. Sequence analysis of partial 16S rRNA gene of GBSRB4.2 revealed that it was affiliated with the genus Desulfosporosinus. GBSRB4.2 reduced sulfate, Fe(III) (hydr)oxide, Mn(IV) oxide, and U(VI) in acidic solutions (pH 4.2). Sulfate, Fe(III), and Mn(IV) but not U(VI) bioreduction led to an increase in the pH of acidic solutions and concurrent hydrolysis and precipitation of dissolved Al³⁺. Reduction of Fe(III), Mn(IV), and U(VI) in sulfate-free solutions revealed that these metals are enzymatically reduced by GBSRB4.2. GBSRB4.2 reduced U(VI) in groundwater from a radionuclide-contaminated aquifer more rapidly at pH 4.4 than at pH 7.1, possibly due to the formation of poorly bioreducible Ca-U(VI)-CO₃ complexes in the pH 7.1 groundwater.

Keywords:

• metal reduction
• acidic mine drainage
• Desulfosporosinus
• sulfate-reducing bacteria

We thank Pam Milavec and Jon Smoyer from the Pennsylvania Department of Environmental Protection for directing us to the Gum Boot system. We thank David Watson from the Oak Ridge National Laboratory for providing groundwater samples. This work was supported by the Pennsylvania Department of Environmental Protection, Bureau of Abandoned Mine Reclamation, the Pennsylvania Water Resources Research Center at the Pennsylvania State University, the Environmental Remediation Science Program (ERSP), Office of Biological and Environmental Research (OBER), Office of Energy Research, US Department of Energy (DOE) grant no. DE-FG02-04ER63914, and the National Science Foundation and US DOE OBER under grant no. CHE-0431328.

Notes

^a Values calculated from Dean (1985).