Stratified water columns support multiple layers of biological activity fueled by oxygenic photosynthesis, anoxygenic photosynthesis, chemolithotrophy and heterotrophy. Our on-going work in the Cariaco and Black Sea shows that biomarker distributions reflect this microbial stratification. Collaborations with the Drs. Jaap Sinninghe Damsté , Stefan Schouten and Ellen Hopmans at the Royal Netherlands Institute for Sea Research (NIOZ) using LC-atmospheric pressure ionization-MS (LC-API-MS) allow us to measure glyceryl dialkyl glyceryl tetraethers (GDGTs), the core membrane lipids unique to archaea, in a variety of samples from our laboratory. Further taxonomic specificity of prokaryotes is achieved analyzing polar "head" groups and apolar "tail" groups which can be obtained using soft ionization MS with positive and negative ion detection. We are collaborating with Dr. Kai-Uwe Hinrichs at the University of Bremen, Germany, in analysis of intact ester (bacterial) and ether-based (archaeal) phospho- and glycolipids in Black Sea-2003 samples by high performance liquid chromatography/electrospray ionization ion trap multistage mass spectrometry (HPLC/ESI-IT-MS n ). |
Isotopic analyses, in collaboration with Dr. Katherine Freeman of Pennsylvania State University, provide a critical connection between biological sources with novel lipid biomarker signatures. Because isotopic gradients can be significant in chemocline systems, evaluation of dissolved inorganic carbon (DIC) can be a very useful way to constrain autotrophic signatures. Sharp chemical and isotopic gradients also exist for methane, and likewise this isotopic signal can be exploited to provide a framework for understanding signatures of methane-consuming organisms via either aerobic or anaerobic metabolisms. Secondary substrates, such as acetate, are recycled efficiently by microbial communities, but will provide an insight to isotopic signatures of heterotrophic communities, and further aiding our efforts to link phylogeny, lipids and metabolic characteristics. Finally, we are working towards linking biomarker distributions and their microbial sources by determining microbial community composition using molecular approaches at the Max Planck Institute for Marine Microbiology in Bremen and with Dr. Gordon Taylor at Stony Brook University.
Selected References :
L. L. King, T. K. Pease and S. G. Wakeham. (1998) Archaea in Black Sea water column particulate matter and sediments: evidence from ether lipid derivatives. Org. Geochem. 28: 677-688.
S. G. Wakeham, C. M. Lewis, E. C. Hopmans, S. Schouten and J. S. Sinninghe Damsté. (2003) Archaea mediate anaerobic oxidation of methane in deep euxinic waters of the Black Sea. Geochim. Cosmochim. Acta 67: 1359-1374.
S. G. Wakeham, E. C. Hopmans, S. Schouten and J. S. Sinninghe Damsté. (2004) Archaeal lipids and anaerobic oxidation of methane in euxinic water columns: a comparative study of the Black Sea and Cariaco Basin. Chem. Geol. 205: 427-442.
X. Lin, S. G. Wakeham, I. F. Putnam, Y. M. Astor, M. I. Scranton, A. Y. Chistoserdov and G. T. Taylor. Vertical distributions of prokaryotic assemblages in the anoxic Cariaco Basin and Black Sea compared using fluorescent in situ hybridization (FISH) techniques. In press. Appl. Environ. Microb.
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