As a microbial ecologist I analyse the composition, diversity, and function of microbial communities with the objective to elucidate ecological relations between microorganisms and their role in biogeochemical cycles. Of particular interest in my previous and current research projects are nitrifying and methane-oxidising microbes. Studying these organisms in their natural habitats, in controlled microcosm experiments as well as in culture I focus on their physiological capabilities and responses to changing environmental conditions, i.e. their ecophysiology. Through these lines of research I want to determine explanations for abundance and activity patterns, (micro)diversity, niches specialization, and quantify ecological importance of these guilds for biochemical cycles in various environments.