He received his Ph.D. in Water and Environmental Studies from Linköping University, Sweden. After a 2.5 year postdoctoral research assistantship in environmental microbiology in Ralph M Parsons' laboratory at Massachusetts Institute of Technology, he returned to Uppsala University in 2002. He now leads a group working with freshwater and marine microbial ecology. His research is focused on microbial population and community dynamics and the role of aquatic bacteria and archaea in the cycling of carbon and associated elements.