October 9th, 2007; Dr. Stephan Schouten
October 9th, 2007
Dr. Stephan Schouten
NIOZ
Abstract
Tetraether membrane lipids: from microbial ecology to ancient sea water temperatures
Membrane lipids of Archaea are distinctly different from that of Bacteria and Eukarya, i.e. they are predominantly composed of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs). This structural difference from diacyl membrane lipids of Eukaryotes and Bacteria was thought to contribute to the thermal stability of membranes of (hyper)thermophilic Archaea. Indeed, Archaea were originally thought to predominate mainly in extreme environments but it has become clear that archaea genetically related to extremophilic archaea are ubiquitous and abundant in many ”normal” environments, i.e. soils, oceans and lakes. At NIOZ we discovered that non-extremophilic Archaea also have GDGTs as their membrane lipids but with some subtle minor structural differences which are likely evolutionary adaptations to low temperature environments. Furthermore, we discovered structurally related GDGTs in soils which stereochemistry suggest that they were made by Bacteria rather than Archaea suggesting that this domain of life is also capable of making membrane-spanning GDGTs.
Upon cell death lipids accumulate in sediments on the bottom of the ocean and can be preserved in rocks, even after hundreds of millions of years. As such they leave an imprint of microbial life as it was in ancient oceans. Research on enrichment cultures of Archaea has shown that they adapt their membrane composition to environmental temperatures. Hence, the analysis of ancient membrane compositions raises the exciting possibility of estimating the temperatures at which these archaea lived. We developed this “paleothermometer” and have applied it to several periods of ancient climatic changes, including high CO2 levels, with sometimes surprising results.
Curriculum vitae
Education
2002-present: Senior Research Scientist at the Department of Marine Biogeochemistry & Toxicology at the Royal Netherlands Institute for Sea Research.
1999 – 2002 : Research Scientist at the Department of Marine Biogeochemistry & Toxicology at the Royal Netherlands Institute for Sea Research.
1998 – 1999 : Visiting Research fellow at the Centre on Polymer Interfaces and Macromolecular Assemblies, University of California at Davis (USA) and Stanford University (USA).
1994 – 1997 : Postdoctoral researcher at the Department of Marine Biogeochemistry & Toxicology at the Netherlands Institute for Sea Research.
1990 – 1994 : PhD-study at the Organic Geochemistry Unit at Delft University of Technology and the Marine Biogeochemistry Division of the Netherlands Institute for Sea Research.
1984 – 1990 : MSc study of chemical technology at Delft University of Technology.
Awards
2005: VICI-award for promising young senior scientists from NWO.
1999: Pieter Schenck Award for best young scientist in organic geochemistry awarded by the European Association of Organic Geochemists.
1997: CPIMA Young Investigator fellowship.
1995: Best Student Paper Award from the organic geochemistry division of the Geochemical Society of America (Geochim.Cosmochim. Acta 59, 953-958)
Schouten 2000
Schouten 2002
Schouten 2004
