Microbial processes in marine habitats are subjected to extreme environmental conditions such as high pressure. One both interesting and essential process in anoxic marine sediments is the anaerobic oxidation of methane (AOM) which is microbially catalysed by a so far unknown mechanism according to the following stoichiometry

Approximately 95% of the methane that is produced in the sediment is effectively removed by AOM before it reaches the water column. Hence, AOM is an important factor regulating the greenhouse gas whose impact is more than 30 times stronger compared to carbon dioxide.
To learn more about this fascinating process it is part of my project to investigate AOM ex-situ in high-pressure biotechnical systems. To effectively simulate in-situ environmental conditions for AOM in the lab particular high-pressure flow-through systems for continuous cultivation needs to be developed. Building shall be started in the beginning of 2005. Using these systems I will investigate how environmental factors influence methane turnover and growth of methanotrophic organisms which were isolated from a large variety of marine sites. We will continuously sample the systems to apply methods of molecular biology, microbiology and biogeochemistry to further elucidate the process of AOM.

Syntrophy in natural and engineered systems in the presence of inorganic surfaces

Syntrophy is known to be crucial for many anaerobic microbial processes in both natural and engineered environments [Schink 1997]. For instance, interspecies hydrogen transfer is one well known mechanism which is often essential for syntrophical degradation of short-chain volatile fatty acids under anaerobic conditions.
However, the study of syntrophic processes is normally difficult since these processes often occur in heterogeneous associations of organisms often in further association with inorganic surfaces.
So it remains unknown if sulfate-dependent anaerobic oxidation of methane is catalysed by a single organism or rather syntrophically by a consortium of a methanogen working in reverse and a sulfate-reducing bacterium with some type of electron transfer between the two organisms. So far there was no success in identifying an electron shuttling compound in AOM. Currently molecular in situ studies suggest that AOM in ocean sediments is mediated to a significant extent by structured consortia of archaea belonging to the order Methanosarcinales (ANME-2 group), and SRB of the Desulfosarcina/Desulfococcus branch of the d-proteobacteria (Boetius et al. 2000, Orphan et al. 2001). A second archaeal group (ANME-1), distantly related to Methanosarcinales, has also been shown to mediate AOM (Orphan et al. 2001, Michaelis et al. 2002).
My interests in investigating syntrophic and putative syntrophic associations concern processes in both marine and terrestrial habitats. I strongly focus on reactions in the presence of inorganic surfaces such as from heavy metal sulfide precipitates following some indications that these compounds might influence syntrophic associations significantly.