1. State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Department of Microbiology, College of Life SciencesNankai University Tianjin 300071 China
2. Department of Molecular Genetics and Microbiology, College of MedicineUniversity of Florida Gainesville FL 32610 USA
3. The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, College of Life SciencesNankai University Tianjin 300071 China