About the Authors
Section of Molecular Genetics and Microbiology and Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America
Department of Microbiology, Morill Science Center, University of Massachusetts at Amherst, Amherst, Massachusetts, United States of America
The authors have declared that no competing interests exist.
Conceived and designed the experiments: SJ SJS RMH. Performed the experiments: SJ. Analyzed the data: SJ SJS RMH. Contributed reagents/materials/analysis tools: SJ SJS. Wrote the paper: RMH.