1. Laboratory of Microbial Interactions, Department of Immunology, Parasitology and Ultrastructure, Flanders Interuniversity Institute of Biotechnology and Vrije Universiteit Brussel, Paardenstraat 65, B-1640 Sint Genesius Rode, Belgium1
2. University of Colorado Health Sciences Center, Microbiology, Box B-175, 4200 E Ninth Avenue, Denver, CO 80202, USA2
3. Laboratoire de Microbiologie et de Génétique, Université Louis Pasteur, UPRES-A 7010, F-67000 Strasbourg, France3
4. Institut für Organische Chemie der Universität zu Köln, Greinstrasse 4,D-50939 Köln, Germany4