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Microbial selenate sorption and reduction in nutrient limited systems
Paul A Kenward1, David A Fowle, Nathan Yee
1Great Lakes Institute for Environmental Research Centre, University of Windsor Canada, Department of Earth and Environmental Sciences, Rutgers, The State University of New Jersey, Newark, New Jersey 07102, USA. pK1@ku.edu
Environmental Science & Technology
|July 13, 2006
Summary
Selenate sorption onto Shewanella putrefaciens 200R is influenced by pH and ionic strength, forming outer-sphere complexes. The bacteria can also reduce selenite to elemental selenium, indicating a combined sorption and reduction process.
Area of Science:
- Environmental Microbiology
- Geochemistry
- Biogeochemistry
Background:
- Microbial interactions with selenium compounds are crucial for understanding selenium cycling in various environments.
- Shewanella putrefaciens 200R is a known bacterium with potential roles in metal and metalloid transformations.
- Selenate is a mobile and potentially toxic form of selenium in aquatic and soil systems.
Purpose of the Study:
- To investigate the mechanisms of selenate sorption onto Shewanella putrefaciens 200R.
- To determine the influence of environmental factors (pH, ionic strength, concentration) on selenate sorption.
- To explore the potential for microbial reduction of selenate by S. putrefaciens.
Main Methods:
- Batch sorption experiments were conducted to assess selenate uptake.
- X-ray adsorption spectroscopy (XAS), including XANES, was used to characterize the chemical state of selenium.
- Sorption was studied across a range of pH, ionic strength, and selenate concentrations.
Main Results:
- Selenate sorption was maximized at low pH (3) and low ionic strength (0.001 M NaCl).
- Results suggest the formation of outer-sphere complexes between selenate and bacterial cell walls.
- XANES analysis revealed the reduction of Se(VI) to elemental selenium (Se(0)) by S. putrefaciens.
Conclusions:
- Selenate sorption onto S. putrefaciens involves both outer-sphere complexation and microbial reduction to Se(0).
- The sorption process creates a complex and not fully reversible selenium reservoir.
- S. putrefaciens can immobilize selenate through a combination of surface binding and biotransformation.
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