Probing the microscopic life found in the submerged recesses of an abandoned Wisconsin lead and zinc mine, scientists have found compelling evidence that microorganisms play a key role in the formation of mineral deposits.
The finding not only sheds light on biology's role in the formation of some metal ores, but could help jump-start new remediation efforts for contaminated mining sites.
Writing in the Friday, Dec. 1, edition of the journal Science, researchers led by Jillian Banfield, a University of Wisconsin-Madison professor of geology and geophysics, describe the discovery and characterization of natural biofilms that seem to concentrate zinc sulfide.
The biofilms, found deep in an abandoned mine, are heavily populated with bacteria, some of which help convert sulfate or sulfuric acid, a pervasive contaminant associated with the mining of metal ores, and zinc from ground water into zinc sulfide.
"These results show how microbes control metal concentrations in ground water and wetland-based remediation systems and suggest biological routes for formation of some low-temperature zinc sulfide deposits," the researchers write in the latest Science, the nation's leading scientific journal.
The biofilms were first discovered by recreational scuba divers exploring the dark, flooded tunnels of an old mine in southwestern Wisconsin, the historic lead mining region near the Mississippi River. Team members trained the divers in the use of sterile collection systems to retrieve samples of the biofilm for laboratory analysis.
In the paper, the Wisconsin team described a process by which tiny zinc sulfide crystals rapidly accumulate within natural biofilms populated by species of sulfate-reducing bacteria. The reduction of sulfate to sulfide, according to Matthias Labrenz, the lead author of the Science paper, is linked to the oxidation of organic matter: as the microbes metabolize organic material, they release sulfide ions into the solution aro
Contact: Jillian Banfield
University of Wisconsin-Madison