1. Symbiotic Function Research Unit, Asian Natural Environmental Science Center, The University of Tokyo, Midori‐cho 1‐1‐8, Nishitokyo‐shi, Tokyo 188‐0002, Japan,
2. Laboratory of Molecular Microbial Ecology and Genomics, College of Life Science and Biotechnology, Shanghai Jiaotong University, Shanghai 200240, China,
3. Department of Biology, Faculty of Science, Toho University, Miyama 2‐2‐1, Funabashi, Chiba 274‐8510, Japan