Bioremediation

L. ochracea colonies in water, site LL1. 60 cc syringe shows scale. Photo credit: USGS Image Gallery

The Environmental Geochemistry and Geomicrobiology (EGG) lab, led by Andrea Foster, has been investigating Iron-oxidizing, iron-reducing, and arsenic-reducing microbial communities at the Lava Cap Mine Superfund site (Nevada City, CA) to understand the interplay between processes that attenuate and mobilize arsenic (As) in surface waters. Sheaths formed by bacteria of the genus Leptothrix physically support a community of ferrous iron-oxidizing bacteria suspended in the water column. This community induces the precipitation of ferric (hydr)oxide which has a high sorptive capacity for As (1000 to > 10,000 mg/kg As, dry-weight). The Environmental Protection Agency is funding this work to determine if the natural arsenic-sorbing capacity of these bacteria can be used to supplement planned arsenic-removal treatment strategies at the site, which must be conducted in perpetuity. Collaborators: A. L. Foster, G. Ona-Nguema (U. of Paris), K. Tufano (Stanford U.), and G. E. Brown, Jr (Stanford U).

For more information contact Andrea L. Foster, Western Mineral Resources Menlo Park Office.

Image Gallery

Putative Leptothrix ochracea collected from site LL1 at Lava Cap Mine, Nevada Cty, CA. Phase-contrast light microscope image showing predominantly empty sheaths characteristic of L. ochracea superimposed on the corresponding epifluorescent image. Using a passive DNA stain, a few filaments of cells can be seen within the sheaths. The overall brown color of the sheath is due to iron (hydr)oxides. Photo credit: USGS