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Phylogenetic and physiological diversity of dissimilatory ferric iron reducers in sediments of the polluted Scheldt estuary, Northwest Europe

Authors

  • Bin Lin,

    1. Department of Molecular Cell Physiology, Faculty of Earth and Life Sciences, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands.
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    • Present addresses: Environment Energy/Health, Agriculture and Agri-Food Canada, Ottawa, ON, Canada K1A OC6;

  • Christelle Hyacinthe,

    1. Department of Earth Sciences – Geochemistry, Faculty of Geosciences, Utrecht University, Budapestlaan 4, Utrecht, the Netherlands.
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  • Steeve Bonneville,

    1. Department of Earth Sciences – Geochemistry, Faculty of Geosciences, Utrecht University, Budapestlaan 4, Utrecht, the Netherlands.
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    • School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.

  • Martin Braster,

    1. Department of Molecular Cell Physiology, Faculty of Earth and Life Sciences, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands.
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  • Philippe Van Cappellen,

    1. Department of Earth Sciences – Geochemistry, Faculty of Geosciences, Utrecht University, Budapestlaan 4, Utrecht, the Netherlands.
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  • Wilfred F. M. Röling

    Corresponding author
    1. Department of Molecular Cell Physiology, Faculty of Earth and Life Sciences, Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands.
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*E-mail Wilfred.roling@falw.vu.nl; Tel. (+31) 20 5987192; Fax (+31) 20 5987229.

Summary

The potential for dissimilatory ferric iron [Fe(III)] reduction in intertidal sediments of the polluted Scheldt estuary, Northwest Europe, was assessed by combining field-based geochemical measurements with laboratory experiments on the associated microbiology. Microbial communities at a freshwater and brackish location were characterized by culture-independent 16S rRNA gene analysis, as well as enrichments, strain isolation and physiological screening. Dilution-to-extinction batch enrichments using a variety of Fe(III) sources were performed. The dilution factor of the inoculum in the enrichments had a more determining effect on the Fe(III)-reducing microbial community structure than the Fe(III) source. Well-known Fe(III) reducers, including members of the family Geobacteraceae and the genus Shewanella, constituted only a small fraction (≤ 1%) of the in situ microbial community. Instead, facultative anaerobic Ralstonia and strictly anaerobic, spore-forming Clostridium species dominated Fe(III) reduction. These species were able to utilize a variety of electron acceptors. This flexibility may help the organisms to survive in the dynamic estuarine environment. The high diversity and abundance of culturable Fe(III) reducers (4.6 × 105 and 2.4 × 104 cells g−1 sediment at the freshwater and brackish site respectively), plus the high concentrations of chemically reducible solid-phase Fe(III) at the sites, implied a high potential for dissimilatory Fe(III) reduction in the estuarine sediments. Pore water chemical data further supported in situ dissimilatory Fe(III) reduction.

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