Microbial diversity and biogeochemistry of the Guaymas Basin deep-sea hydrothermal plume

Authors

  • Gregory J. Dick,

    1. Marine Biology Research Division and
    2. Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0202, USA.
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    • Present address: Department of Geological Sciences, University of Michigan, 1100 N. University Avenue, Ann Arbor, MI 48109-1005, USA;

  • Bradley M. Tebo

    Corresponding author
    1. Marine Biology Research Division and
    2. Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0202, USA.
      E-mail tebo@ebs.ogi.edu; Tel. (+1) 503 748 1992; Fax (+1) 503 748 1464.
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    • Division of Environmental and Biomolecular Systems, Oregon Health & Sciences University, 20000 NW Walker Rd., Beaverton, OR 97006, USA.


E-mail tebo@ebs.ogi.edu; Tel. (+1) 503 748 1992; Fax (+1) 503 748 1464.

Summary

Hydrothermal plumes are hot spots of microbial biogeochemistry in the deep ocean, yet little is known about the diversity or ecology of microorganisms inhabiting plumes. Recent biogeochemical evidence shows that Mn(II) oxidation in the Guaymas Basin (GB) hydrothermal plume is microbially mediated and suggests that the plume microbial community is distinct from deep-sea communities. Here we use a molecular approach to compare microbial diversity in the GB plume and in background deep seawater communities, and cultivation to identify Mn(II)-oxidizing bacteria from plumes and sediments. Despite dramatic differences in Mn(II) oxidation rates between plumes and background seawater, microbial diversity and membership were remarkably similar. All bacterial clone libraries were dominated by Gammaproteobacteria and archaeal clone libraries were dominated by Crenarchaeota. Two lineages, both phylogenetically related to methanotrophs and/or methylotrophs, were consistently over-represented in the plume. Eight Mn(II)-oxidizing bacteria were isolated, but none of these or previously identified Mn(II) oxidizers were abundant in clone libraries. Taken together with Mn(II) oxidation rates measured in laboratory cultures and in the field, these results suggest that Mn(II) oxidation in the GB hydrothermal plume is mediated by genome-level dynamics (gene content and/or expression) of microorganisms that are indigenous and abundant in the deep sea but have yet to be unidentified as Mn(II) oxidizers.

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