Fourier-Transformations-Ionenzyklotronresonanz-Massenspektrometer
Final Report Abstract
The 15 Tesla FT-ICR-MS is the highest resolving mass spectrometer that is commercially available. It is located at and operated by the Research Group for Marine Geochemistry at the Institute for Chemistry and Biology of the Marine Environment (ICBM) at the Carl von Ossietzky University Oldenburg. We are currently the only marine research institute worldwide that operates such ultrahigh-resolution mass spectrometer. This technology provides us with a unique tool for non-targeted metabolite analysis by which a comprehensive overview of a metabolome is obtained on a molecular formula level. Our research focus for the application of this mass spectrometry technique is the geo-metabolome of the ocean, or dissolved organic matter (DOM). DOM in natural aquatic systems plays a vital role for life on Earth. It links organic matter production and decay in the water column because algal products can only be taken up by microbial consumers as small dissolved molecules. Most of DOM is turned over by microorganisms within hours and days after production. A small fraction of DOM, however, resists microbial degradation. This refractory fraction of DOM has persisted in the ocean for thousands of years, and has accumulated to the largest pool of organic carbon in the ocean, containing more than a thousand times more carbon than all living organisms in the oceans combined. DOM provides an important feedback mechanism in the climate system, because minor changes in the DOM pool could considerably impact atmospheric carbon dioxide concentrations and the radiation balance on Earth. Our research that involves FT-ICR-MS covers four main themes. (1) Reasons behind the millennium-scale stability of DOM. (2) Molecular interactions between microorganisms. (3) Application of novel concepts in biogeochemical systems. (4) Method development. DOM is an extraordinarily diverse molecular mixture. At some point, each individual molecule in DOM has its specific function and reactivity in the cycling of energy and elements, and in the chemical interaction among aquatic organisms. We seek to understand DOM dynamics and interactions with microorganisms on a molecular and potentially mechanistic level. Geo-metabolomics considers the entity of DOM as a population of compounds. Conventional targeted metabolite analyses have very limited analytical windows, and only a small fraction of existing metabolites has been described on a molecular level. After extensive method development and improvement, we have, in several projects, collaboratively collected large sets of DOM molecular data and genome sequencing data, for freshwater and marine environments, and experimental settings. The molecular data on DOM, obtained from FT-ICR-MS, rival in detail the molecular metagenome data obtained via the various sequencing techniques on natural aquatic microbial communities. In selected cases, additional targeted molecular analyses with the FT-ICR-MS provide information on the molecular structures behind the identified molecular formulae. Insights from field studies are complemented by controlled laboratory experiments where fully-sequenced organisms are grown as pure strains or mixed cultures under various growth conditions. One of our principal observations is that far more compounds are being excreted by microorganisms than what is known to be encoded in the genome. My research group in Oldenburg has become a central place for colleagues from around the world that share a common interest in the new field of geo-metabolomics. Discerning linkages between the several thousand taxonomic units and DOM molecules is a major challenge and a common objective of the various projects. We have approached this goal from different angles, and established a global network of renowned experts in aquatic biogeochemistry, marine and freshwater microbiology, microbial ecology, and mathematical modeling.
Publications
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(2012) Biogeochemically diverse organic matter in glaciers in European Alps. Nature Geoscience 5, 710-714
Singer GA, Fasching C, Wilhelm L, Niggemann J, Steier P, Dittmar T and Battin TJ
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(2012) Molecular fractionation of dissolved organic matter with metal salts. Environmental Science and Technology 46, 4419-4426
Riedel T, Biester H and Dittmar T
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(2013) Global charcoal mobilization from soils via dissolution and riverine transport to the oceans. Science 340, 345-347
Jaffé R, Ding Y, Niggemann J, Vähätalo AV, Campbell J and Dittmar T
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(2013) Iron traps terrestrially derived dissolved organic matter at redox interfaces. Proceedings of the National Academy of Sciences PNAS 110, 10101-10105
Riedel T, Zak D, Biester H and Dittmar T
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(2013) Molecular composition of dissolved organic matter from a wetland plant (Juncus effusus) after photochemical and microbial decomposition (1.25 yr): Common features with deep sea dissolved organic matter. Organic Geochemistry 60, 6271
Rossel PE, Vähätalo AV, Witt M and Dittmar T
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(2014) A method detection limit for the analysis of natural organic matter via Fourier transform ion cyclotron resonance mass spectrometry. Analytical Chemistry 86, 8376-8382
Riedel T and Dittmar T
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(2014) Biogeochemistry of dissolved organic matter in an anoxic intertidal creek bank. Geochimica et Cosmochimica Acta 140, 418-434
Seidel M., Beck M, Riedel T, Waska H, Suryaputra IGNA, Schnetger B, Niggemann J, Simon M and Dittmar T
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(2014) Chemodiversity of dissolved organic matter in lakes driven by climate and hydrology. Nature Communications 5, 3804,1-8
Kellermann AM, Dittmar T, Kothawala DN and Tranvik LJ
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(2014) Exo-metabolome of Pseudovibrio sp. FO-BEG1 analyzed by ultra-high resolution mass spectrometry and the effect of phosphate limitation. PLOS One 9 (5) e96038
Romano S, Dittmar T, Bondarev V, Weber RJM, Viant MR and Schulz-Vogt HN
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(2014) Molecular evidence for rapid dissolved organic matter turnover in Arctic fjords. Marine Chemistry 160, 1-10
Osterholz H, Dittmar T, Niggemann J
