T11 PM Developments in Bioremediation of Acid Mine Drainage Wastes
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 343-344

(COL-1118-698064) Metal toxicity and bacterial sulfate reduction: what do we really know?

Colberg, P¹, Jin, S², ¹ University of Wyoming, Laramie, WY, USA² Western Research Institute, Laramie, WY, USA

ABSTRACT- Natural deposits of heavy metals typically occur as sulfide minerals that are insoluble under low redox conditions. Since reduction of sulfate to sulfide at surface temperatures and pressures occurs only via microbial processes, the mobility of heavy metals in anoxic environments is, in effect, controlled by microbial activity. The resultant sulfides are known to precipitate heavy metals, immobilizing them as sulfide minerals or as trace constituents of other metal sulfides. Because bacterial sulfate reduction in known to play a major role in the fate of organic contaminants, many of which coexist with metals, understanding interactions between heavy metals and sulfate-reducing bacteria (SRB) is imperative to advancing applications of SRB to ameliorating both metal and organic contamination problems in a variety of environmental settings. Only a small number of studies have focused on metal tolerance by SRB. We have investigated the tolerance of sulfate-reducing sediment enrichments to a range of metal concentrations. Our results demonstrate that SRB can efficiently detoxify metals; but more importantly, our work suggests that the apparent tolerance of SRB to metals is not likely based solely on their ability to release sulfides that bind metals. Clearly, more research is warranted to identify the precise mechanisms involved in metal tolerance in SRB and to elucidate differences in community composition and structure from a wider field of anaerobic settings. This presentation will both summarize and assess the findings of studies from a broad spectrum of applications that have focused on SRB and metal toxicity.

Key words: metal toxicity, bacterial sulfate reduction