1. Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
2. Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
3. Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
4. Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
5. Center for Bioinformatics and Computational Biology, University of Maryland, College Park, Maryland, USA