Evidence for rapid microscale bacterial redox cycling of iron in circumneutral environments |
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Authors: | Sobolev Dmitri Roden Eric E |
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Institution: | (1) Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487-0206, USA |
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Abstract: | The potential for microscale bacterial Fe redox cycling was investigated in microcosms containing ferrihydrite-coated sand
and a coculture of a lithotrophic Fe(II)-oxidizing bacterium (strain TW2) and a dissimilatory Fe(III)-reducing bacterium (Shewanella alga strain BrY). The Fe(II)-oxidizing organism was isolated from freshwater wetland surface sediments which are characterized
by steep gradients of dissolved O2 and high concentrations of dissolved and solid-phase Fe(II) within mm of the sediment–water interface, and which support
comparable numbers (105–106 mL−1) of culturable Fe(II)-oxidizing and Fe(III)-reducing reducing. The coculture systems showed minimal Fe(III) oxide accumulation
at the sand-water interface, despite intensive O2 input from the atmosphere and measurable dissolved O2 to a depth of 2 mm below the sand–water interface. In contrast, a distinct layer of oxide precipitates formed in systems
containing Fe(III)-reducing bacteria alone. Examination of materials from the cocultures by fluorescence in situ hybridization
indicated close physical juxtapositioning of Fe(II)-oxidizing and Fe(III)-reducing bacteria in the upper few mm of sand. Our
results indicate that Fe(II)-oxidizing bacteria have the potential to enhance the coupling of Fe(II) oxidation and Fe(III)
reduction at redox interfaces, thereby promoting rapid microscale cycling of Fe.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | bacteria cycling Fe iron oxidation redox reduction |
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