Mineralogy Drives Bacterial Biogeography of Hydrothermally Inactive Seafloor Sulfide Deposits

Abstract

Mid-ocean ridge hydrothermal venting creates sulfide deposits containing gradients in mineralogy, fluid chemistry, and temperature. Even when hydrothermal circulation ceases, sulfides are known to host microbial communities. The relationship between mineralogy and microbial community composition in low-temperature, rock-hosted systems has not been resolved at any spatial scale, local or global. To examine the hypothesis that geochemistry of seafloor deposits is a dominant parameter driving environmental pressure for bacterial communities at low-temperature, the shared community membership, richness, and structure was measured using 16S rRNA gene sequences. The focus of the study was on hydrothermally inactive seafloor deposits from multiple locations within one deposit (e.g., single extinct chimney), within one vent field (intra-vent field), and among globally distributed vent fields from three ocean basins (inter-vent field). Distinct mineral substrates, such as hydrothermally inactive sulfides versus basalts, host different communities at low temperature in spite of close geographic proximity and contact with the same hydrothermally influenced deep-sea water. Furthermore, bacterial communities inhabiting hydrothermally inactive sulfide deposits from geographically distant locations cluster together in community cladograms to the exclusion of other deep-sea substrates and settings. From this study, we conclude that at low temperature, mineralogy was a more important variable determining microbial community composition than geographic factors. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the supplemental file.

Keywords:

• basalts
• East Pacific Rise
• microbial ecology
• mid-ocean ridge
• sulfides

Acknowledgments

We thank PD Schloss and JA Huber for discussions regarding community comparisons and data treatment; JA Huber and WJ Brazelton for unpublished data; M. Manno and L. Sauer of the University of Minnesota Characterization Facility for assistance with X-ray diffraction; DR Rogers for sample collection. For financial support we thank the NASA Astrobiology Institute (NNA04CC04A); the National Research Council Associate and NASA Postdoctoral Programs (BMT); RIDGE 2000 (OCE-0241791; KJE and WB); CFANS University of Minnesota (BMT); Woods Hole Oceanographic Institution's Summer Student Fellow program (JJM); the DFG-Research Center/Excellence Cluster The Ocean in the Earth System (WB), and the Danish National Research Foundation and the Max Planck Society (BNO). Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program.