Effects of Electron Donor and Sulfate on Iron Reduction and Microbial Community Development

Effects of Electron Donor and Sulfate on Iron Reduction and Microbial Community Development
권만재Dion A. AntonopoulosMaxim I. BoyanovJennifer BrulcKenneth KemnerEdward J. O'Loughlin
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In situ bioremediation is one option for reducing levels of contaminants. Introducing suitable substrates into the subsurface can stimulate the growth of iron and/or sulfate reducing microorganisms which often reduce contaminants either directly or by the production of reactive Fe(II) and sulfur species. We investigated 1) the effects of electron donors on the enrichment of specific communities and 2) the effects of sulfate reduction on FeIII (hydr)oxide reduction and microbial community development. Aquifer sediment was incubated with several electron donors (i.e., acetate, lactate, or glucose) and acceptors (i.e., ferrihydrite, goethite, or lepidocrocite) in the presence or absence of sulfate. Terminal Restriction Fragment Length Polymorphism (T-RFLP) was used to monitor changes in the microbial communities. Mineral transformations were monitored using x-ray absorption fine-structure (XAFS) analysis. In the absence of sulfate, FeIII reduction was slow and limited. However, in the presence of sulfate, the extent of FeIII reduction increased more than 10 times. The sulfate reduction occurred concurrently with FeIII reduction suggesting abiotic FeIII reduction by sulfide. XAFS analysis confirmed the presence of iron sulfide as the major secondary mineral phases in these incubations. All electron donors promoted FeIII reduction, but with different rates and extents: glucose>lactate>acetate. T-RFLP yielded unique community profiles depending upon the availability of specific electron donors, FeIII (hydr)oxides, and sulfate. This study suggests that the availability of specific electron donors, iron minerals, and sulfate strongly influences mineral transformation as well as microbial community structure.
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