Stratified prokaryote network in the oxic–anoxic transition of a deep-sea halocline

The chemical composition of the Bannock basin has been studied in some detail. We recently showed that unusual microbial populations, including a new division of Archaea (MSBL1), inhabit the NaCl-rich hypersaline brine. High salinities tend to reduce biodiversity, but when brines come into contact with fresher water the natural haloclines formed frequently contain gradients of other chemicals, including permutations of electron donors and acceptors, that may enhance microbial diversity, activity and biogeochemical cycling. Here we report a 2.5-m-thick chemocline with a steep NaCl gradient at 3.3 km within the water column betweeen Bannock anoxic hypersaline brine and overlying sea water. The chemocline supports some of the most biomass-rich and active microbial communities in the deep sea, dominated by Bacteria rather than Archaea, and including four major new divisions of Bacteria. Significantly higher metabolic activities were measured in the chemocline than in the overlying sea water and underlying brine; functional analyses indicate that a range of biological processes is likely to occur in the chemocline. Many prokaryotic taxa, including the phylogenetically new groups, were confined to defined salinities, and collectively formed a diverse, sharply stratified, deep-sea ecosystem with sufficient biomass to potentially contribute to organic geological deposits.

[1]  Claude E. Shannon,et al.  The Mathematical Theory of Communication , 1950 .

[2]  D. Wiesenburg,et al.  Microbial Biomass and Activity Distribution in an Anoxic, Hypersaline Basin , 1979, Applied and environmental microbiology.

[3]  A. Roychoudhury,et al.  Biogeochemical Cycles of Manganese and Iron at the Oxic-Anoxic Transition of a Stratified Marine Basin (Orca Basin, Gulf of Mexico) , 1998 .

[4]  K. Timmis,et al.  Microbial enzymes mined from the Urania deep-sea hypersaline anoxic basin. , 2005, Chemistry & biology.

[5]  H. Cypionka,et al.  Ongoing Modification of Mediterranean Pleistocene Sapropels Mediated by Prokaryotes , 2002, Science.

[6]  G. Luther,et al.  Sulphur speciation in anoxic hypersaline sediments from the eastern Mediterranean Sea , 1997 .

[7]  K. Timmis,et al.  The Enigma of Prokaryotic Life in Deep Hypersaline Anoxic Basins , 2005, Science.

[8]  Robert Huber,et al.  Prokaryotic phylogenetic diversity and corresponding geochemical data of the brine-seawater interface of the Shaban Deep, Red Sea. , 2002, Environmental microbiology.

[9]  G. Luther,et al.  Reduced sulfur in the hypersaline anoxic basins of the Mediterranean sea , 1990 .

[10]  D. Canfield,et al.  Aerobic sulfate reduction in microbial mats. , 1991, Science.

[11]  Gerald R. Dickens,et al.  Distributions of Microbial Activities in Deep Subseafloor Sediments , 2004, Science.

[12]  G. Luther,et al.  The interface between oxic seawater and the anoxic Bannock brine; its sharpness and the consequences for the redox-related cycling of Mn and Ba , 1990 .

[13]  E. Delong,et al.  Archaeal dominance in the mesopelagic zone of the Pacific Ocean , 2001, Nature.

[14]  J. Overmann,et al.  Functional Exoenzymes as Indicators of Metabolically Active Bacteria in 124,000-Year-Old Sapropel Layers of the Eastern Mediterranean Sea , 2000, Applied and Environmental Microbiology.

[15]  Frede Thingstad,et al.  Prokaryotic genetic diversity throughout the salinity gradient of a coastal solar saltern. , 2002, Environmental microbiology.

[16]  Wolfgang Eder,et al.  Novel 16S rRNA gene sequences retrieved from highly saline brine sediments of Kebrit Deep, Red Sea , 1999, Archives of Microbiology.

[17]  C. E. SHANNON,et al.  A mathematical theory of communication , 1948, MOCO.

[18]  T. Herbert,et al.  Gypsum precipitation from cold brines in an anoxic basin in the eastern Mediterranean , 1985, Nature.

[19]  C. Sorlini,et al.  Comparison of Different Primer Sets for Use in Automated Ribosomal Intergenic Spacer Analysis of Complex Bacterial Communities , 2004, Applied and Environmental Microbiology.

[20]  Peter G. Brewer,et al.  Methane-consuming archaebacteria in marine sediments , 1999, Nature.

[21]  K. Schleifer,et al.  ARB: a software environment for sequence data. , 2004, Nucleic acids research.

[22]  T. Pearson,et al.  Comparative measurement of the redox potential of marine sediments as a rapid means of assessing the effect of organic pollution , 1979 .

[23]  F. Azam,et al.  Protein content and protein synthesis rates of planktonic marine bacteria , 1989 .

[24]  D. Hydes,et al.  Composition of anoxic hypersaline brines in the Tyro and Bannock Basins, eastern Mediterranean , 1990 .

[25]  Andrew J. Weightman,et al.  Deep sub-seafloor prokaryotes stimulated at interfaces over geological time , 2005, Nature.

[26]  Wolfgang Eder,et al.  Microbial Diversity of the Brine-Seawater Interface of the Kebrit Deep, Red Sea, Studied via 16S rRNA Gene Sequences and Cultivation Methods , 2001, Applied and Environmental Microbiology.

[27]  G. Lange,et al.  The distribution of DOC and POC in the water column and brines of the Tyro and Bannock Basins , 1990 .

[28]  K. Horikoshi,et al.  Rapid Detection and Quantification of Members of the Archaeal Community by Quantitative PCR Using Fluorogenic Probes , 2000, Applied and Environmental Microbiology.

[29]  D. Stahl,et al.  Unexpected Population Distribution in a Microbial Mat Community: Sulfate-Reducing Bacteria Localized to the Highly Oxic Chemocline in Contrast to a Eukaryotic Preference for Anoxia , 1999, Applied and Environmental Microbiology.

[30]  J. Willison,et al.  Molecular sequence analysis of prokaryotic diversity in the anoxic sediments underlying cyanobacterial mats of two hypersaline ponds in Mediterranean salterns. , 2003, FEMS microbiology ecology.