1 Department of Gastroenterology and Hepatology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
2 Department of Microbiology and Immunology, Rega Institute for Medical Research, Leuven, Belgium.
3 Center for Microbiology, VIB-KU Leuven, Leuven, Belgium.
4 Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
5 Department of Gastroenterology and Hepatology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands r.k.weersma@umcg.nl.