1. Albrecht-von-Haller Institute for Plant Sciences, Department for Molecular Biology of Plant-Microbe Interaction; Georg-August-University Göttingen; Julia-Lermontowa-Weg 3 37077 Göttingen Germany
2. Institute of Applied Microbiology, Department of Microbial Genetics; RWTH Aachen University; Worringerweg 1 52074 Aachen Germany