A Deep Sea Brine Interface Teeming With New Life

Newly Discovered Bacteria Form a Complex Ecosystem


In the latest issue of the prestigious science journal, Nature, a European team reports the discovery of diverse new microbial communities in an unusual deepsea environment. Several so-called brine “lakes”, distinct salt-saturated water bodies underneath the water column of the Mediterranean Sea, formed thousands of years ago by dissolution of rock salt exposed by geological events. These “lakes under the sea” are 3-4 km below sea surface and represent extreme environments for living organisms: they are characterized by high pressure (400x atmospheric pressure) and salinity (10x saltier than seawater), and lack oxygen. Because of their high densities, brine lakes do not mix with the overlying water and thus have been isolated from the rest of the biosphere for a very long time. Professor Timmis of the German Research Centre for Biotechnology (GBF) in Braunschweig, a member of the team that explored the brine lakes, explains: “Despite the fact that such environments exist on our planet, we know so little about them that their exploration is as exciting as interplanetary missions. The big question was: do they contain new forms of life?” In order to answer this question, several expeditions to sample the basins have taken place in the framework of the BIODEEP Project funded by the European Commission.

Impressive Variety
In their Nature paper, the BIODEEP team reports the discovery of flourishing diverse communities containing novel microbes in the brine lake:water column transition zone of the Bannock Basin located off the coast of North Africa. The diversity and high populations of microbes in an environment hostile to life surprised the researchers. Apparently, the high density of the brine traps dead organisms and their products drifting down through the water column to create a transition zone high in organic material that can support a rich community of salt-and pressure-tolerant microbes specialized to live without oxygen. Moreover, the steep salinity and oxygen gradients across the interface create a sequence of discrete and distinct environments, some just centimetres thick, and each with different concentrations of compounds like sugars, sulfates, nitrates and manganese (compounds used in place of oxygen to extract energy from food), that provide diverse habitats for distinct communities: a stratification of habitats and communities. Many new microbes, including 4 new Divisions of Bacteria unrelated to any known organisms, were discovered, and 84 could be isolated in culture for further study.

“Our current investigations indicate that phylogenetic diversity reflects functional diversity, that is: new organisms have new activities and make new bioproducts with potential for medical and chemical applications”, says Timmis. “The discrete stratified habitats of the brine lake interfaces constitute exceptional conditions in which novel organisms have evolved. Systematic exploration of these and other extreme environments, and characterization of the biological properties of the new organisms found, will undoubtedly lead to important discoveries about life processes and interesting new biotechnological applications.”

Additional Information for the Media
More detailed information can be found in the original article: D. Daffonchio, S. Borin, T. Brusa, L. Brusetti, P. van der Wielen, H. Bolhuis, M. Yakimov, G. D’Auria, L. Giuliano, D. Marty, C. Tamburini, T. McGenity, J. Hallsworth, A. Sass, K. Timmis, A. Tselepides, G. de Lange, A. Hübner, J. Thomson, S. Varnavas, F. Gasparoni, H. Gerber, E. Malinverno, C. Corselli & Biodeep Scientific Party: Stratified Prokaryote Network in the Oxic-Anoxic Transition of a Deep-Sea Halocline. Nature, 9 March 2006, Vol 440, No. 7081, pp 203-207.