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Decoupling microbial iron reduction from anoxic microsite formation in oxic sediments: a microscale investigation
Giulia Ceriotti1, Alice Bosco-Santos1, Sergey M Borisov2
1Faculty of Geoscience and Environment, Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland.
Frontiers in Microbiology
|February 12, 2025
Summary
Microbial iron reduction, an ancient anaerobic process, was found to occur even in oxygen-rich environments. This challenges previous assumptions and suggests iron reduction may be more widespread in subsurface soils and vadose zones.
Area of Science:
- Microbiology
- Geochemistry
- Environmental Science
Background:
- Iron (Fe) reduction is a critical microbial process, historically confined to anoxic environments.
- Evidence suggests Fe reduction occurs in oxic subsurface zones, attributed to undetected anoxic microsites.
- Understanding microscale oxygen dynamics is key to explaining Fe reduction in partially saturated systems.
Purpose of the Study:
- To investigate the regulation of microbial Fe reduction by microscale oxygen concentrations.
- To explore the occurrence of Fe reduction under fully oxic conditions.
Main Methods:
- Cultivation of a facultative Fe-reducing bacterium in a microfluidic device.
- Integration of transparent planar oxygen sensors for real-time monitoring.
- Mathematical modeling of oxygen dynamics around biomass-rich layers.
Main Results:
- Microbial Fe reduction was observed under fully oxic conditions, contrary to expectations.
- Anoxic microsites were not required for Fe reduction in this study.
- Biomass spatial organization, not water saturation, primarily controls anoxic microsite formation.
Conclusions:
- Microbially mediated Fe reduction may be more prevalent in oxic subsurface environments than previously thought.
- Biomass spatial organization is a critical factor in predicting anoxic microsite formation and Fe(III) reduction.
- This study offers a new perspective on the factors governing Fe reduction in subsurface environments.
Keywords:
Shewanella oneidensisanoxic micrositesdiffusioniron cycleiron reductionmicrofluidicsoxygenplanar sensorsMore Related Videos
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