Cosmiverse.com
December 01, 2000
A new method of cleaning up contaminated water to be used as drinking water is described in the December 1st issue of Science. Tiny bacteria that help convert dissolved zinc actually remove impurities from water, converting the impurities into zinc sulfide crystals called sphalerite. According to the interdisciplinary U.S. and Australian research team, the bacteria, known for its ability to naturally form sulfides, are helping scientists understand how zinc ore deposits were formed in intricate natural systems throughout time.
The bacteria were removed from a flooded tunnel by scuba divers in Tennyson, Wisconsin. When scientists studied the samples, they found that in this specific family of bacteria, known as Desulfobacteriaceae, microscopic beads of sphalerite are created within a sort of protective "biofilm" that binds a microbial community together. The beads, or "aggregates", measure up to 10 nanometers each in diameter, and cluster from the bacteria. Each aggregate can hold up to a billion zinc sulfide particles and can even hold trace amounts of selenium and arsenic.
According to Matthias Labrenz of the University of Wisconsin-Madison, while some species of sulfate-reducing bacteria do better in environments lacking oxygen, other species thrive at low levels of aeration, it is these species in which scientists can use sulfide precipitation to biologically remove elements from contaminated water. These bacteria may have played a part in prehistoric geochemical cycles before the Earth had a substantial amount of oxygen in the atmosphere. Zinc sulfide ore deposits found from this geological period support this theory.
The scientists X-rayed the bacteria and found that the aggregates in the biofilm are made up of pure zinc sulfide. Geochemical modeling confirmed that the concentration of zinc was as low as one part per million in the groundwater where the bacteria caused sphalerite precipitation at low temperatures.
Source: AAAS Press Release
Related Links: American Association for the Advancement of Science (AAAS)
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