Stefan Bertilsson is a Professor of Biology at the Department of Ecology and Genetics at Uppsala University and the Director of the Microbial Single Cell Genomics Facility at Science for Life Laboratory. He obtained his PhD from the interdisciplinary Department of Water and Environmental Studies at LInköping University focusing on the impact of photochemical processes on aquatic bacteria and carbon cycling in lakes and oceans. After a 3 year postdoc at the Massachusetts Institute of Technology, working on single cell methods and molecular tools for microbial community analyses, he moved to the Limnology Department at Uppsala University in 2002. He and his research group in aquatic microbial ecology study linkages between microbial diversity, metabolic function and biogeochemical cycling of carbon, nitrogen, mercury and other reactive elements. Metagenome and rRNA sequencing, isotope tracer methods and single cell genome analyses are key methods and are applied to microbial communities in a wide range of ecosystems ranging from the deep biosphere, to lakes and the Southern Ocean.