1. Department of Microbiology, University of Colorado Denver, School of Medicine, Aurora, Colorado, USA
2. Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado, USA
3. Department of Microbiology and Immunology, Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, New York, USA
4. Department of Microbiology, University of Minnesota, Minneapolis, Minnesota, USA