1. Department of Microbiology, University of Iowa, Iowa City, Iowa, USA;
2. University of Chicago, Department of Biochemistry and Molecular Biology, Chicago, Illinois, USA;
3. U.S. Department of State, Bureau of Economic and Business Affairs, Office of Agriculture, Biotechnology, and Textile Trade Affairs, Washington, DC, USA;
4. Harvard Medical School, Department of Microbiology and Immunobiology, Boston, Massachusetts, USA