1. Department of Microbiology, Institute for Water and Wetland Research Radboud University Heyendaalseweg 135 Nijmegen 6525 AJ The Netherlands
2. Netherlands Earth System Science Center Utrecht University, Heidelberglaan 2 Utrecht 3584 CS The Netherlands
3. Soehngen Institute of Anaerobic Microbiology Radboud University, Heyendaalseweg 135 Nijmegen 6525 AJ The Netherlands