1. Humboldt-University Berlin, Institute of Biology, Chausseestr. 117, 10115 Berlin, Germany
2. Max Planck Institute for Infection Biology, Charitéplatz 1, 10117 Berlin, Germany
3. University of Freiburg, Faculty of Biology, Schänzlestr. 1, 79104 Freiburg, Germany
4. Justus-Liebig University Giessen, Institute of Microbiology and Molecular Biology, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany