Long-distance electron transfer by cable bacteria in aquifer sediments

Publication: Research - peer-reviewJournal article

DOI

  • Hubert Müller
    Hubert MüllerInstitute of Groundwater Ecology, Helmholtz Zentrum MünchenGermany
  • Julian Bosch
    Julian BoschInstitute of Groundwater Ecology, Helmholtz Zentrum MünchenGermany
  • Christian Griebler
    Christian GrieblerInstitute of Groundwater Ecology, Helmholtz Zentrum MünchenGermany
  • Lars Riis Damgaard
  • Lars Peter Nielsen
  • Tillmann Lueders
    Tillmann LuedersInstitute of Groundwater Ecology, Helmholtz Zentrum MünchenGermany
  • Rainer Meckenstock
    Rainer MeckenstockInstitute of Groundwater Ecology, Helmholtz Zentrum MünchenGermany
The biodegradation of organic pollutants in aquifers is often restricted to the fringes of contaminant plumes where steep countergradients of electron donors and acceptors are separated by limited dispersive mixing. However, long-distance electron transfer (LDET) by filamentous ‘cable bacteria’ has recently been discovered in marine sediments to couple spatially separated redox half reactions over centimeter scales. Here we provide primary evidence that such sulfur-oxidizing cable bacteria can also be found at oxic–anoxic interfaces in aquifer sediments, where they provide a means for the direct recycling of sulfate by electron transfer over 1–2-cm distance. Sediments were taken from a hydrocarbon-contaminated aquifer, amended with iron sulfide and saturated with water, leaving the sediment surface exposed to air. Steep geochemical gradients developed in the upper 3 cm, showing a spatial separation of oxygen and sulfide by 9 mm together with a pH profile characteristic for sulfur oxidation by LDET. Bacterial filaments, which were highly abundant in the suboxic zone, were identified by sequencing of 16S rRNA genes and fluorescence in situ hybridization (FISH) as cable bacteria belonging to the Desulfobulbaceae. The detection of similar Desulfobulbaceae at the oxic–anoxic interface of fresh sediment cores taken at a contaminated aquifer suggests that LDET may indeed be active at the capillary fringe in situ.
Original languageEnglish
JournalThe I S M E Journal
Volume10
Pages (from-to)2010-2019
Number of pages10
ISSN1751-7362
DOIs
StatePublished - 8 Apr 2016

    Keywords

  • Cable bacteria, Groundwater contamination

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