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Dissolution and reduction of magnetite by bacteria
1Center for Great Lakes Studies, University of Wisconsin, Milwaukee 53204, USA.
Environmental Science & Technology
|October 1, 1995
Summary
The bacterium Shewanella putrefaciens rapidly reduces magnetite (Fe3O4), a key iron oxide in sediments. This biological process, coupled to metabolism, impacts sediment magnetism and diagenesis.
Area of Science:
- Geomicrobiology
- Environmental Science
- Geochemistry
Background:
- Magnetite (Fe3O4), an iron oxide, is crucial for geomagnetism and sediment diagenesis.
- Understanding magnetite stability is vital for interpreting sedimentary magnetic records, including ocean floor spreading.
- While chemical reduction by sulfide is known, biological reduction was previously considered unlikely.
Purpose of the Study:
- To investigate the potential for biological reduction of magnetite by bacteria.
- To determine the conditions and mechanisms of magnetite reduction by Shewanella putrefaciens.
- To assess the significance of bacterial magnetite reduction in natural environments.
Main Methods:
- Utilized marine and freshwater strains of Shewanella putrefaciens.
- Quantified magnetite dissolution and reduction to soluble Fe(II).
- Investigated optimal conditions (pH, temperature) and requirements (viable cells, cell contact, electron donors).
Main Results:
- Shewanella putrefaciens rapidly reduced millimolar amounts of magnetite to soluble Fe(II) within days.
- Optimal reduction occurred at pH 5-6 and 22-37°C, suggesting an enzymatic process.
- Magnetite reduction was dependent on viable cells, cell contact, and coupled to electron transport, growth, and carbon metabolism.
Conclusions:
- Marine and freshwater Shewanella putrefaciens can biologically reduce magnetite.
- Bacterial magnetite reduction rates are comparable to sulfide reduction rates.
- This microbial remobilization of magnetite may significantly influence sediment magnetism and diagenesis.