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Manganese oxides preci-pitated around a spore (cell) of the marine Mn(II)-oxidizing bacterium, Bacillus sp., strain SG-1.

Science Highlight


31 August 2005

  The Mighty Manganese Oxides

summary written by Heather Rock Woods, SLAC Communication Office

John R. Bargar, Samuel M. Webb (SSRL) and Bradley M. Tebo (Oregon Health and Sciences University)


Manganese oxides form in the oceanic water column as a result of the bacterially catalyzed oxidation of a relatively abundant form of dissolved manganese. As they settle through the water column, manganese oxides participate in myriad chemical reactions important to sea life and to maintaining the trace-metal composition of sea water. These reactions profoundly impact the geochemical cycling of carbon, nitrogen, sulfur, nutrients and containments.

Before, scientists did not know the identities of the bacteria-derived manganese oxides. A collaborative group of scientists from SSRL and the Oregon Health and Science University have used two synchrotron-based techniques to determine the identities of manganese oxides formed in sea water by a marine bacterium. The conclusion from both sets of measurements is that the manganese oxide produced in sea water is a poorly crystalline layered manganese oxide called birnessite. Identifying marine manganese oxides will substantially enhance scientists' ability to model and understand their roles in maintaining the chemistry of the oceans. This information will also directly contribute to a greater understanding of the properties of bacteriogenic manganese oxides, which are of great interest for their potential technological applications.