1. Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
2. Department of Membrane Enzymology, Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
3. Laboratoire des Symbioses Tropicales et Méditerranéennes, Campus International de Baillarguet, TA 10/J, 34398 Montpellier cedex 5, France
4. FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands