Letter

Nature 440, 203-207 (9 March 2006) | doi:10.1038/nature04418; Received 18 October 2005; Accepted 9 November 2005

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

Daniele Daffonchio1, Sara Borin1, Tullio Brusa1, Lorenzo Brusetti1, Paul W. J. J. van der Wielen2, Henk Bolhuis2, Michail M. Yakimov3, Giuseppe D'Auria3, Laura Giuliano3, Danielle Marty4, Christian Tamburini4, Terry J. McGenity5, John E. Hallsworth5, Andrea M. Sass5, Kenneth N. Timmis5,6, Anastasios Tselepides7, Gert J. de Lange8, Andreas Hübner8, John Thomson9, Soterios P. Varnavas10, Francesco Gasparoni11, Hans W. Gerber12, Elisa Malinverno13 and Cesare Corselli13 and Biodeep Scientific Party

The chemical composition of the Bannock basin has been studied in some detail1, 2. We recently showed that unusual microbial populations, including a new division of Archaea (MSBL1)3, inhabit the NaCl-rich hypersaline brine. High salinities tend to reduce biodiversity4, 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 cycling5, 6. 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 brine7 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. CoNISMa, Ulr Università degli Studi di Milano, DiSTAM, 20133 Milan, Italy
  2. Department of Microbial Ecology, CEES, University of Groningen, 9751 NN Haren, The Netherlands
  3. Istituto per l'Ambiente Marino Costiero, CNR, 98122 Messina, Italy
  4. LMGEM, UMR 6117 CNRS Université de la Mediterranée, 13288 Marseille, France
  5. Department of Biological Sciences, University of Essex, Colchester, Essex CO4 3SQ, UK
  6. Division of Microbiology, GBF, 38122 Braunschweig, Germany
  7. Institute of Marine Biology of Crete, 71003 Heraklion, Greece
  8. Faculty of Geosciences, Geochemistry, Utrecht University, 3584 CD Utrecht, The Netherlands
  9. Southampton Oceanography Centre, Southampton SO14 3EE, UK
  10. Department of Geology, University of Patras, 26100 Patras, Greece
  11. Tecnomare S.p.A., ENI Group, 30124 Venice, Italy
  12. Technische Fachhochschule Berlin, University of Applied Science, 13353 Berlin, Germany
  13. CoNISMa, Ulr Università degli Studi di Milano Bicocca, DGSG, 20126 Milan, Italy
  14. LMGEM, UMR 6117 CNRS Université de la Mediterranée, 13288 Marseille, France
  15. Department of Biological Sciences, University of Essex, Colchester, Essex CO4 3SQ, UK
  16. Division of Microbiology, GBF, 38122 Braunschweig, Germany
  17. Institute of Marine Biology of Crete, 71003 Heraklion, Greece
  18. Tecnomare SpA, ENI group, 30124 Venice, Italy
  19. Technische Fachhochschule Berlin, University of Applied Science, 13353 Berlin, Germany

Correspondence to: Daniele Daffonchio1 Correspondence and requests for materials should be addressed to D.D. (Email: daniele.daffonchio@unimi.it). The newly determined 16S rRNA sequences have been submitted to the DDBJ/NCBI/GenBank database under accession numbers AM157647–AM157656, AY547745–AY547866 and DQ289238–DQ289401.

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