1. Universität Osnabrück, Fachbereich Biologie/Chemie, Abteilung Mikrobiologie, Barbarastrasse 11, D-49069 Osnabrück, Germany
2. School of Medical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom
3. Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, PO Box 951569, Los Angeles, CA 90095
4. Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada N1G 2W1