1. Department of Genetics, University of Wisconsin-Madison, Madison, WI, USA
2. Department of Bacteriology and J. F. Crow Institute for the Study of Evolution, University of Wisconsin-Madison, Madison, WI, USA
3. Applied Bioinformatics, Department of Computer Science, Quantitative Biology Center and Center for Bioinformatics, University of Tübingen, Tübingen, Germany
4. Biomolecular Interactions, Max Planck Institute for Developmental Biology, Tübingen, Germany
5. Bioinformatics Group, Wageningen University, Wageningen, The Netherlands