1. Department of Molecular Genetics, University of Toronto, Toronto, Canada.
2. Department of Earth Sciences, University of Toronto, Toronto, Canada.
3. NASA Goddard Space Flight Center, Greenbelt, Maryland, USA.
4. Department of Physics, Catholic University of America, Washington, DC, USA.
5. Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA.
6. Department of Microbiology and Plant Pathology, University of California, Riverside, California, USA.
7. Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.
8. Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island, USA.
9. Department of Molecular Genetics and Microbiology, Medicine, and Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, USA.