1. Toxinology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrict, Frederick, Maryland 21702‐5011, USA.
2. Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrict, Frederick, Maryland 21702‐5011, USA.
3. Molecular Control and Genetics Section, Laboratory of Chromosome Biology, ABL‐Basic Research Program, NCI‐Frederick Cancer Research and Development Center, Frederick, Maryland 21702‐1201, USA.