About the Authors
Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, United States of America
Department of Microbiology, University of Chicago, Cummings Life Science Center, Chicago, Illinois, United States of America
The authors have declared that no competing interests exist.
Conceived and designed the experiments: IF NS HAS. Performed the experiments: IF NS. Analyzed the data: IF NS. Contributed reagents/materials/analysis tools: HAS. Wrote the paper: IF HAS.