Microbial life in ridge flank crustal fluids

Authors

  • Julie A. Huber,

    Corresponding author
    1. University of Washington, School of Oceanography, Center for Astrobiology and Early Evolution, Box 357940 Seattle, WA 98195, USA.
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    • Present address: Josephine Bay Paul Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA.

  • H. Paul Johnson,

    1. University of Washington, School of Oceanography, Box 357940, Seattle, WA 98195, USA.
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  • David A. Butterfield,

    1. Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, NOAA/PMEL, 7600 Sand Point Way NE, Seattle, WA 98115, USA.
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  • John A. Baross

    1. University of Washington, School of Oceanography, Center for Astrobiology and Early Evolution, Box 357940 Seattle, WA 98195, USA.
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*E-mail jhuber@mbl.edu; Tel. (+1) 508 548 3705, x6616; Fax (+1) 508 457 4727.

Summary

To determine the microbial community diversity within old oceanic crust, a novel sampling strategy was used to collect crustal fluids at Baby Bare Seamount, a 3.5 Ma old outcrop located in the north-east Pacific Ocean on the eastern flank of the Juan de Fuca Ridge. Stainless steel probes were driven directly into the igneous ocean crust to obtain samples of ridge flank crustal fluids. Genetic signatures and enrichment cultures of microorganisms demonstrate that these crustal fluids host a microbial community composed of species indigenous to the subseafloor, including anaerobic thermophiles, and species from other deep-sea habitats, such as seawater and sediments. Evidence using molecular techniques indicates the presence of a relatively small but active microbial population, dominated by bacteria. The microbial community diversity found in the crustal fluids may indicate habitat variability in old oceanic crust, with inputs of nutrients from seawater, sediment pore-water fluids and possibly hydrothermal sources. This report further supports the presence of an indigenous microbial community in ridge flank crustal fluids and advances our understanding of the potential physiological and phylogenetic diversity of this community.

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