Jan Schröder

PhD project:

Archaeal biomarkers in marine sediments: improved protocols for analysis andapplications to current problems in biogeochemistry of the deep biosphere

Marine sediments are inhabited by microorganisms that are degrading organic matter, thus affecting the chemical composition of ocean and atmosphere over geological timescales. Investigating microbial communities and processes within the sediments is necessary to understand the biogeochemical element cycles on earth. There is evidence that beneath those microbes Archaea, a third domain besides Eukarya and Bacteria, is abundant and ubiquitously distributed in deep subseafloor sediments and play a key role in mediating degradation processes in this deep biosphere.

One promising approach to study role and distribution of Archaea is to analyze their cell components. Therefore intact polar lipids (IPL) - the building blocks of microbial membranes - have been successfully applied as biomarkers in a variety of environmental samples. Due to their taxonomic specificity and property to select for live biomass, IPLs offer a detailed view of abundance and composition of microbial communities. However the existing protocols for IPL analysis face analytical frontiers. Most environmental samples comprise a very complex mixture of organic compounds and pose a challenge to separation and identification. Typical problems are low IPL concentrations combined with a high background of sample matrix. These issues can be overcome by efficient extract clean-up and sample pre-concentration followed by improved HPLC-MS methods.

In a first step I work on optimization of analysis of those lipids by improving the already existing methods and clean-up protocols and using state-of-the-art instrumentation like HPLC-qTOF-MS. Afterwards, I will apply those advanced methods to environmental samples (e.g., samples taken during the DARC-SEAS cruise Meteor 48-1 in the eastern Mediterranean, Marmara and Black Seas in February 2011) seeking a more detailed lipid signature of Archaea. This advanced knowledge of archaeal biomarkers can contribute to a better understanding of the deep biosphere itself and its role in the global system.

Research Area: C "Marine Ecology and Biogeochemistry"