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Deep biosphere-related bacteria within the subsurface of tidal flat sediments

Authors

  • Reinhard Wilms,

    1. Institut für Chemie und Biologie des Meeres, Universität Oldenburg, Carl-von-Ossietzky Straße, 9-11, D-26129 Oldenburg, Germany.
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  • Beate Köpke,

    1. Institut für Chemie und Biologie des Meeres, Universität Oldenburg, Carl-von-Ossietzky Straße, 9-11, D-26129 Oldenburg, Germany.
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  • Henrik Sass,

    1. Institut für Chemie und Biologie des Meeres, Universität Oldenburg, Carl-von-Ossietzky Straße, 9-11, D-26129 Oldenburg, Germany.
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    • Present address: School of Earth, Ocean and Planetary Sciences, Cardiff Uni, Main Building, Park Place, Cardiff CF10 3YE, Wales, UK;

  • Tae Soo Chang,

    1. Institut für Chemie und Biologie des Meeres, Universität Oldenburg, Carl-von-Ossietzky Straße, 9-11, D-26129 Oldenburg, Germany.
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    • Senckenberg Institute, Division of Marine Science, Südstrand 40, D-26382 Wilhelmshaven, Germany.

  • Heribert Cypionka,

    1. Institut für Chemie und Biologie des Meeres, Universität Oldenburg, Carl-von-Ossietzky Straße, 9-11, D-26129 Oldenburg, Germany.
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  • Bert Engelen

    Corresponding author
    1. Institut für Chemie und Biologie des Meeres, Universität Oldenburg, Carl-von-Ossietzky Straße, 9-11, D-26129 Oldenburg, Germany.
      *E-mail engelen@icbm.de; Tel. (+49) 441 798 5376; Fax (+49) 441 798 3583.
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*E-mail engelen@icbm.de; Tel. (+49) 441 798 5376; Fax (+49) 441 798 3583.

Summary

Biogeochemical and microbiological processes in the upper sediment layers of tidal flats were analysed in many investigations, while deeper zones remained largely unexplored. Therefore, denaturant gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments along the depth profile of up to 5.5 m-long sediment cores was performed in comparison with lithological and geochemical parameters. The investigation revealed that different compartments of the sediment columns were characterized by specific microbial communities. These compartments were analysed by sequencing of 113 DGGE bands. The upper layers down to 160–200 cm were dominated by gamma- and delta-Proteobacteria representing more than 60% of the total number of phylotypes. Underneath, a striking shift in community composition was observed, as the Proteobacteria were replaced by Chloroflexi with more than 60% of all sequences. As sulfate was still available as an electron acceptor in these layers, the abundance of Chloroflexi might be promoted by the electron donor or the quality of the carbon source. The dominance of this group, previously known as green non-sulfur bacteria, indicates the presence of a typical deep-biosphere microbial community in relatively young subsurface sediments. Thus, tidal flats might offer a convenient possibility to study and understand certain aspects of the deep biosphere in general.

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