Distinct dissolved organic matter sources induce rapid transcriptional responses in coexisting populations of Prochlorococcus, Pelagibacter and the OM60 clade

Authors

  • Adrian K. Sharma,

    1. Departments of Civil and Environmental Engineering and Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
    2. Center for Microbial Oceanography: Research and Education (C-MORE), Honolulu, HI, USA
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    • These authors contributed equally to this work.
  • Jamie W. Becker,

    1. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
    2. Center for Microbial Oceanography: Research and Education (C-MORE), Honolulu, HI, USA
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    • These authors contributed equally to this work.
  • Elizabeth A. Ottesen,

    1. Departments of Civil and Environmental Engineering and Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
    2. Department of Microbiology, University of Georgia, Athens, GA, USA
    3. Center for Microbial Oceanography: Research and Education (C-MORE), Honolulu, HI, USA
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  • Jessica A. Bryant,

    1. Departments of Civil and Environmental Engineering and Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
    2. Center for Microbial Oceanography: Research and Education (C-MORE), Honolulu, HI, USA
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  • Solange Duhamel,

    1. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
    2. Lamont Doherty Earth Observatory, Columbia University, Palisades, NY, USA
    3. Center for Microbial Oceanography: Research and Education (C-MORE), Honolulu, HI, USA
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  • David M. Karl,

    1. Department of Oceanography, School of Ocean and Earth Science and Technology (SOEST), University of Hawaii, Honolulu, HI, USA
    2. Center for Microbial Oceanography: Research and Education (C-MORE), Honolulu, HI, USA
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  • Otto X. Cordero,

    1. Departments of Civil and Environmental Engineering and Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
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  • Daniel J. Repeta,

    1. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
    2. Center for Microbial Oceanography: Research and Education (C-MORE), Honolulu, HI, USA
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  • Edward F. DeLong

    Corresponding author
    1. Departments of Civil and Environmental Engineering and Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
    2. Center for Microbial Oceanography: Research and Education (C-MORE), Honolulu, HI, USA
    • For correspondence. E-mail delong@mit.edu; Tel. (+1) 617 253 5271; Fax (+1) 617 253 2679.

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Summary

A considerable fraction of the Earth's organic carbon exists in dissolved form in seawater. To investigate the roles of planktonic marine microbes in the biogeochemical cycling of this dissolved organic matter (DOM), we performed controlled seawater incubation experiments and followed the responses of an oligotrophic surface water microbial assemblage to perturbations with DOM derived from an axenic culture of Prochlorococcus, or high-molecular weight DOM concentrated from nearby surface waters. The rapid transcriptional responses of both Prochlorococcus and Pelagibacter populations suggested the utilization of organic nitrogen compounds common to both DOM treatments. Along with these responses, both populations demonstrated decreases in gene transcripts associated with nitrogen stress, including those involved in ammonium acquisition. In contrast, responses from low abundance organisms of the NOR5/OM60 gammaproteobacteria were observed later in the experiment, and included elevated levels of gene transcripts associated with polysaccharide uptake and oxidation. In total, these results suggest that numerically dominant oligotrophic microbes rapidly acquire nitrogen from commonly available organic sources, and also point to an important role for carbohydrates found within the DOM pool for sustaining the less abundant microorganisms in these oligotrophic systems.

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