1. Division of Bioenvironmental Science, Frontier Science Research Center, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan
2. Division of Microbiology, Department of Infectious Disease, Faculty of Medicine, University of Miyazaki, 5200 Kiyotake, Miyazaki 889-1692, Japan
3. Division of Cell and Molecular Biology, Imperial College London, London SW7 2AZ, UK