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Microbial lithotrophic oxidation of structural Fe(II) in biotite
Evgenya Shelobolina1, Huifang Xu, Hiromi Konishi
1Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin, USA. shelobolina@wisc.edu
Applied and Environmental Microbiology
|June 12, 2012
Summary
Microbes can directly weather biotite by oxidizing structural iron (Fe(II)), initiating mineral breakdown. This microbial iron oxidation releases essential elements and alters mineral structure, impacting geological processes.
Area of Science:
- Geochemistry
- Microbiology
- Mineralogy
Background:
- Microorganisms influence mineral weathering through organic acid production and nutrient uptake.
- Biotite, a common mica in granitic rocks, contains structural Fe(II) that is susceptible to oxidation.
Purpose of the Study:
- To investigate the ability of a specific lithotrophic Fe(II)-oxidizing, nitrate-reducing bacterium to grow by oxidizing structural Fe(II) in biotite.
- To characterize the mineralogical and chemical changes in biotite resulting from microbial oxidation.
Main Methods:
- Utilized a microbial enrichment culture known for lithotrophic Fe(II) oxidation.
- Analyzed biotite samples using Mössbauer spectroscopy to confirm structural Fe(II) oxidation.
- Quantified microbial growth yield based on Fe(II) oxidation.
Main Results:
- The enrichment culture successfully grew by oxidizing structural Fe(II) in biotite, evidenced by decreased extractable Fe(II) and nitrate reduction.
- Mössbauer spectroscopy confirmed the oxidation of structural Fe(II) within the biotite lattice.
- Microbial oxidation led to biotite alterations including decreased b dimension and release of Fe and K, mimicking natural weathering.
Conclusions:
- Microbial oxidation of structural Fe(II) is a significant initial step in biotite weathering.
- This process occurs in environments like granitic aquifers and the plant rhizosphere.
- Direct enzymatic oxidation is favored over indirect mechanisms due to the absence of soluble iron.
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