1. Institute for Microbiology and Biotechnology, University of Bonn, Meckenheimer Allee 168, 53115 Bonn, Germany
2. Theoretical Biology, University of Bonn, Kirschallee 1, 53115 Bonn, Germany
3. Centre for Systems Biology, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK