The research focus is on understanding and changing close dependencies between microbiological entities. This involves the interaction of microbes in symbiotic relationships, but the main focus is on endosymbiotic organelles (i.e. chloroplasts and mitochondria) and their embedding within eukaryotic cells. The photosynthetic green microalga Chlamydomonas reinhardtii is our most important model system. Our current research focuses on the mechanism and evolution of protein import into chloroplasts. Analogously, we are investigating whether protein import can be generated in the model bacterium Escherichia coli. Protein import in bacteria is expected to provide a new way to establish dependencies between interacting microbial species. Methodologically, fluorescence microscopy, biochemical and molecular approaches, physiological measurements and experimental evolution are being used.