1. Kekulé Institute of Organic Chemistry and Biochemistry, University of Bonn, D-53121 Bonn, Germany
2. Institute for Pharmaceutical Microbiology, University Clinic Bonn, University of Bonn, D-53115 Bonn, Germany
3. German Center for Infection Research (DZIF), Partner Site Bonn-Cologne, Germany
4. Pharmaceutical Institute, Dept. of Pharmaceutical Biology, University of Tübingen, D-72076 Tübingen, Germany