Research focuses on bacterial evolution and its functional implications, including those in different microbiomes. The mechanisms of bacterial adaptation and diversification are studied by comparative genomics, population genomics, and phenotypic analyses, employing selected model organisms with relevance in the environment, in human medicine, and veterinary medicine. In addition, microbial functions in complex microbiomes are resolved through the identification of keystone species and their specific activities, employing culture-independent sequencing, multivariate statistical, and modeling approaches. This also extends to subfossil molecular remains of past microbial communities. As a third research topic, we elucidate the molecular mechanisms of mutualistic bacterial interactions (bacterial heterologous multicellularity) and their evolutionary origins.