The distribution of active iron-cycling bacteria in marine and freshwater sediments is decoupled from geochemical gradients

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DOI

  • Julia M. Otte, Univ Tubingen, Eberhard Karls University of Tubingen, Ctr Appl Geosci, Geomicrobiol
  • ,
  • Johannes Harter, Univ Tubingen, Eberhard Karls University of Tubingen, Ctr Appl Geosci, Geomicrobiol
  • ,
  • Katja Laufer
  • Nia Blackwell, Univ Tubingen, Eberhard Karls University of Tubingen, Microbial Ecol, Ctr Appl Geosci
  • ,
  • Daniel Straub, Univ Tubingen, Eberhard Karls University of Tubingen, Microbial Ecol, Ctr Appl Geosci
  • ,
  • Andreas Kappler
  • Sara Kleindienst, Univ Tubingen, Eberhard Karls University of Tubingen, Microbial Ecol, Ctr Appl Geosci

Microaerophilic, phototrophic and nitrate-reducing Fe(II)-oxidizers co-exist in coastal marine and littoral freshwater sediments. However, the in situ abundance, distribution and diversity of metabolically active Fe(II)-oxidizers remained largely unexplored. Here, we characterized the microbial community composition at the oxic-anoxic interface of littoral freshwater (Lake Constance, Germany) and coastal marine sediments (Kalo Vig and Norsminde Fjord, Denmark) using DNA-/RNA-based next-generation 16S rRNA (gene) amplicon sequencing. All three physiological groups of neutrophilic Fe(II)-oxidizing bacteria were found to be active in marine and freshwater sediments, revealing up to 0.2% anoxygenic photoferrotrophs (e.g., Rhodopseudomonas, Rhodobacter, Chlorobium), 0.1% microaerophilic Fe(II)-oxidizers (e.g., Mariprofundus, Hyphomonas, Gallionella) and 0.3% nitrate-reducing Fe(II)-oxidizers (e.g., Thiobacillus, Pseudomonas, Denitromonas, Hoeflea). Active Fe(III)-reducing bacteria (e.g., Shewanella, Geobacter) were most abundant (up to 2.8%) in marine sediments and co-occurred with cable bacteria (up to 4.5%). Geochemical profiles of Fe(III), Fe(II), O-2, light, nitrate and total organic carbon revealed a redox stratification of the sediments and explained 75%-85% of the vertical distribution of microbial taxa, while active Fe-cycling bacteria were found to be decoupled from geochemical gradients. We suggest that metabolic flexibility, microniches in the sediments, or interrelationships with cable bacteria might explain the distribution patterns of active Fe-cycling bacteria.

Original languageEnglish
JournalEnvironmental Microbiology
Volume20
Issue7
Pages (from-to)2483-2499
Number of pages17
ISSN1462-2912
DOIs
Publication statusPublished - Jul 2018

    Research areas

  • SULFATE-REDUCING BACTERIA, PALUSTRIS STRAIN TIE-1, FERROUS-IRON, CABLE BACTERIA, COMMUNITY STRUCTURE, NITRATE REDUCTION, FE(II) OXIDATION, ORGANIC-MATTER, SEQUENCE DATA, GALLIONELLA-FERRUGINEA

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