Iron-Oxide Minerals Affect Extracellular Electron-Transfer Paths of <i>Geobacter</i> spp.

  • Kato Souichiro
    Hashimoto Light Energy Conversion Project, ERATO, JST
  • Hashimoto Kazuhito
    Hashimoto Light Energy Conversion Project, ERATO, JST Research Center for Advanced Science and Technology, The University of Tokyo Department of Applied Chemistry, The University of Tokyo
  • Watanabe Kazuya
    School of Life Sciences, Tokyo University of Pharmacy and Life Sciences Department of Applied Chemistry, The University of Tokyo Hashimoto Light Energy Conversion Project, ERATO, JST

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Other Title
  • Iron-Oxide Minerals Affect Extracellular Electron-Transfer Paths of Geobacter spp
  • Iron-oxide minerals affect extracellular electron-transfer paths of <italic>Geobacter</italic> spp

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Abstract

Some bacteria utilize (semi)conductive iron-oxide minerals as conduits for extracellular electron transfer (EET) to distant, insoluble electron acceptors. A previous study demonstrated that microbe/mineral conductive networks are constructed in soil ecosystems, in which Geobacter spp. share dominant populations. In order to examine how (semi)conductive iron-oxide minerals affect EET paths of Geobacter spp., the present study grew five representative Geobacter strains on electrodes as the sole electron acceptors in the absence or presence of (semi)conductive iron oxides. It was found that iron-oxide minerals enhanced current generation by three Geobacter strains, while no effect was observed in another strain. Geobacter sulfurreducens was the only strain that generated substantial amounts of currents both in the presence and absence of the iron oxides. Microscopic, electrochemical and transcriptomic analyses of G. sulfurreducens disclosed that this strain constructed two distinct types of EET path; in the absence of iron-oxide minerals, bacterial biofilms rich in extracellular polymeric substances were constructed, while composite networks made of mineral particles and microbial cells (without polymeric substances) were developed in the presence of iron oxides. It was also found that uncharacterized c-type cytochromes were up-regulated in the presence of iron oxides that were different from those found in conductive biofilms. These results suggest the possibility that natural (semi)conductive minerals confer energetic and ecological advantages on Geobacter, facilitating their growth and survival in the natural environment.<br>

Journal

  • Microbes and Environments

    Microbes and Environments 28 (1), 141-148, 2013

    Japanese Society of Microbial Ecology / Japanese Society of Soil Microbiology / Taiwan Society of Microbial Ecology / Japanese Society of Plant Microbe Interactions / Japanese Society for Extremophiles

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