1. Mycobacteriology Research Laboratory, William S. Middleton Memorial Veterans Hospital, Madison, WI 53705, USA
2. Chemical Biology & Therapeutics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
3. Department of Chemistry, University of Wisconsin, Madison, WI 53706, USA
4. Department of Bacteriology, University of Wisconsin, Madison, WI 53706, USA