1. Department of Biosystems Science and Engineering, ETH Zurich, Mattenstrasse 26, CH-4058 Basel, Switzerland.
2. Département Génie Biologique, Institut Universitaire de Technologie, F-69622 Villeurbanne Cedex, France.
3. Faculty of Science, University of Basel, Mattenstrasse 26, CH-4058 Basel, Switzerland.