1. Institute of Microbiology; Leibniz Universität Hannover; Herrenhäuser Str. 2 Hannover 30419 Germany
2. Institute of Biochemistry and Biotechnology; Martin-Luther University Halle-Wittenberg; Kurt-Mothes-Straße 3 Halle (Saale) 06120 Germany
3. Max Planck Institute for Biophysical Chemistry; Am Fassberg 11 Göttingen 37077 Germany