1. Department of Biology, Washington University in St. Louis, St. Louis, Missouri, USA
2. Department of Molecular Microbiology and Microbial Pathogenesis, Washington University School of Medicine, St. Louis, Missouri, USA
3. Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
4. Division of Infectious Diseases, John T. Milliken Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA