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Fall 2017 Seminar Series


Dr. Eric Roden presents “Extracellular electron transfer (EET) in the critical zone"

401 Steidle Building

Dr. Eric Roden, Albert and Alice Weeks Professor of Geoscience, University of Wisconsin-Madison, presents "Extracellular electron transfer (EET) in the critical zone:  biological redox transformation of insoluble Fe-bearing minerals in soil and sedimentary environments” in 401 Steidle Building 


Iron (Fe) bearing oxide, sulfide, and silicate minerals are important components of natural soils, sediments, and aquifers – i.e. the subsurface realm of the critical zone. Such phases engage in redox reactions with inorganic and organic compounds that impact a wide variety of geological and environmental process, such as sediment diagenesis, chemical weathering, and the mobility and fate of organic and inorganic contaminants. Because Fe-bearing minerals are typically highly insoluble in circumneutral pH, near-surface environments, their redox transformation takes place by way of chemical reactions at the mineral-water interface. In the case of microbially-mediated pathways, these redox reactions rely on processes external to the cell surface, which are referred to collectively as “extracellular electron transfer” (EET). Reductive EET pathways have been studied extensively in the context of microorganisms that couple heterotrophic metabolism to dissimilatory reduction of Fe(III) oxides and other oxidized metal species. Less is known about oxidative EET metabolism, particularly in relation to weathering of insoluble Fe(II)-bearing sulfide and silicate phases. This presentation will focus on oxidative EET pathways in a subsurface redox transition zone at the Hanford 300 Area research site in eastern Washington state, and at the bedrock-saprolite interface at the Luquillo Mountains CZO site in Puerto Rico. A combination of in situ geochemistry, microbiological experimentation, and genomic sequencing sheds light on previously unrecognized pathways whereby microorganisms may accelerate oxidative weathering of insoluble Fe(II)-bearing mineral phases.

For our off-campus collaborators, you may join the meeting via Zoom meetings:

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