Cornelia U Welte1. 1. Radboud University, Institute for Water and Wetland Research, Department of Microbiology, Heyendaalseweg 135, 6525AJ Nijmegen, Netherlands. Soehngen Institute of Anaerobic Microbiology, Heyendaalseweg 135, 6525AJ Nijmegen, Netherlands. c.welte@science.ru.nl.