Publications

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Publications in peer reviewed journals

3 Publications found
  • Depth distribution and assembly of sulfate-reducing microbial communities in marine sediments of Aarhus Bay

    Jochum LM, Chena X, Lever MA, Loy A, Jørgensen BB, Schramm A, Kjeldsen KU
    2017 - Appl Environ Microbiol, In press

    Abstract: 

    Most sulfate-reducing microorganisms (SRM) present in subsurface marine sediments belong to uncultured groups only distantly related to known SRM and it remains unclear how changing geochemical zones and sediment depth influence their community structure. We mapped the community composition and abundance of SRM by amplicon-sequencing and quantifying dsrB, which encodes dissimilatory sulfite reductase subunit beta, in sediment samples covering different vertical geochemical zones ranging from the surface sediment to the deep sulfate-depleted subsurface at four locations in Aarhus Bay, Denmark. SRM were present in all geochemical zones including sulfate-depleted methanogenic sediment. The biggest shift in SRM community composition and abundance occurring across the transition from bioturbated surface sediments into non-bioturbated sediments below, where redox fluctuations and input of fresh organic matter due to macrofaunal activity are absent. SRM abundance correlated with sulfate reduction rates determined for the same sediments. Sulfate availability showed weaker correlation with SRM abundances and no significant correlation with the composition of the SRM community. The overall SRM species diversity decreased with depth, yet we identified a subset of highly abundant community members that persists across all vertical geochemical zones of all stations. We conclude that subsurface SRM communities assemble by persistence of members of the surface community and that the transition from the bioturbated surface sediment to the unmixed sediment below is a main site of assembly of the subsurface SRM community.

  • Evidence for H2 consumption by uncultured Desulfobacterales in coastal sediments.

    Dyksma S, Pjevac P, Ovanesov K, Greuter L
    2017 - Environ. Microbiol., In press

    Abstract: 

    Molecular hydrogen (H2 ) is the key intermediate in the anaerobic degradation of organic matter. Its removal by H2 -oxidizing microorganisms is essential to keep anaerobic degradation energetically favorable. Sulfate-reducing microorganisms (SRM) are known as the main H2 scavengers in anoxic marine sediments. Although the community of marine SRM has been extensively studied, those consuming H2 in situ are completely unknown. We combined metagenomics, PCR-based clone libraries, single-amplified genomes (SAGs) and metatranscriptomics to identify potentially H2 -consuming SRM in anoxic coastal sediments. The vast majority of SRM-related H2 ase sequences were assigned to group 1b and 1c [NiFe]-H2 ases of the deltaproteobacterial order Desulfobacterales. Surprisingly, the same sequence types were similarly highly expressed in spring and summer, suggesting that these are stable and integral members of the H2 -consuming community. Notably, one sequence cluster from the SRM group 1 consistently accounted for around half of all [NiFe]-H2 ase transcripts. Using SAGs, we could link this cluster with the 16S rRNA genes of the uncultured Sva0081-group of the family Desulfobacteraceae. Sequencing of 16S rRNA gene amplicons and H2 ase gene libraries suggested consistently high in situ abundance of the Sva0081 group also in other marine sediments. Together with other Desulfobacterales these likely are important H2 -scavengers in marine sediments. This article is protected by copyright. All rights reserved.

  • The life sulfuric: Microbial ecology of sulfur cycling in marine sediments.

    Wasmund K, Mussmann M, Loy A
    2017 - Environ Microbiol Rep, 9: 323-344

    Abstract: 

    Almost the entire seafloor is covered with sediments that can be more than 10,000 m thick and represent a vast microbial ecosystem that is a major component of Earth's element and energy cycles. Notably, a significant proportion of microbial life in marine sediments can exploit energy conserved during transformations of sulfur compounds among different redox states. Sulfur cycling, which is primarily driven by sulfate reduction, is tightly interwoven with other important element cycles (carbon, nitrogen, iron, manganese) and therefore has profound implications for both cellular- and ecosystem-level processes. Sulfur-transforming microorganisms have evolved diverse genetic, metabolic, and in some cases, peculiar phenotypic features to fill an array of ecological niches in marine sediments. Here, we review recent and selected findings on the microbial guilds that are involved in the transformation of different sulfur compounds in marine sediments and emphasize how these are interlinked and have a major influence on ecology and biogeochemistry in the seafloor. Extraordinary discoveries have increased our knowledge on microbial sulfur cycling, mainly in sulfate-rich surface sediments, yet many questions remain regarding how sulfur redox processes may sustain the deep-subsurface biosphere and the impact of organic sulfur compounds on the marine sulfur cycle. This article is protected by copyright. All rights reserved.

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