1. Department of Microbiology, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands
2. Department of Molecular Cell Biology, Electron Microscopy Group, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
3. Department of Microbiology and Parasitology (JAF)/Centre for Microscopy and Microanalysis (RIW), University of Queensland, Brisbane, QLD 4072, Australia