Molecular characterization of microbial populations in methane-rich marine habitats

The anaerobic oxidation of methane (AOM) with sulfate is a globally important microbial process, catalyzed by syntrophic consortia of marine anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB). The main objective of this thesis was to gain further insights into AOM habitats and communities by using biogeochemical and molecular techniques.One chapter of this thesis provides first insights into the abundance and distribution of ANME and SRB at cold seep sites from the coastal margin off New Zealand, far away from all known ANME habitats. Another part describes new insights into the abundance and distribution of ANME and SRB in microbial reefs from the Black Sea shelf, the most intensively studied ANME habitats. Chloroflexi related cells were identified as additional key reef bacteria accounting for up to 28% of all cells. Another chapter deals with the identification and quantification of Verrucomicrobia in a humic lake. Further, this thesis gives insights into the quantification of ANME by real time PCR and ANME-3 genomic analysis after cell sorting by flow cytometry.