1. Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA, Division of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
2. Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
3. Computational and Systems Biology Initiative, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
4. Whitehead Institute For Biomedical Research, Cambridge, Massachusetts 02139, USA
5. Institute of Medical Microbiology and Hospital Epidemiology, Hannover Medical School, Hannover, Germany
6. Division of Comparative Medicine, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA, jgfox@ mit.edu