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Sulfur-Mediated Electron Shuttling During Bacterial Iron Reduction

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Science  01 May 2014:
1252066
DOI: 10.1126/science.1252066

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Abstract

Microbial reduction of ferric iron [Fe(III)] is an important biogeochemical process in anoxic aquifers. Depending on groundwater pH, dissimilatory metal-reducing bacteria can also respire alternative electron acceptors to survive, including elemental sulfur (S0). To understand the interplay of Fe/S cycling under alkaline conditions, we combined thermodynamic geochemical modeling with bioreactor experiments using Shewanella oneidensis MR-1. Under these conditions, S. oneidensis can enzymatically reduce S0 but not goethite (α-FeOOH). The HS produced subsequently reduces goethite abiotically. Due to the prevalence of alkaline conditions in many aquifers, Fe(III) reduction may thus proceed via S0–mediated electron-shuttling pathways.

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