Microbe Metabolism Aids Metal Cleanup

At a former vanadium- and uranium-processing site in Colorado, geomicrobiologists have uncovered a community of anaerobic bacteria that make a living through diverse metabolisms, some of which have never been seen before in bacteria (Science, 10.1126/science.1224041). The discovery could aid bioremediation of contaminated sites to remove toxic heavy metals. To stimulate bacterial growth at the contaminated site, Jillian F. Banfield of the University of California, Berkeley, and colleagues added acetate to the aquifer. They then took water samples from the aquifer and sequenced the total DNA of the microbial community, which included 87 microbes. Through this metagenomic survey they found metal-reducing bacteria that commonly bloom upon addition of acetate. They also found 49 bacteria that ferment organic carbon to produce hydrogen and organic compounds, including acetate. The fermenting organisms could be harnessed to help sustain the beneficial metal-reducing bacteria at contaminated sites, Banfield says. Several of the 49 bacteria use metabolic pathways that involve sulfur reduction and couple fermentation with carbon dioxide fixation, which were previously found only in archaeal microorganisms.