1. Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523, USA
2. Department of Microbiology, The Ohio State University, Columbus, OH 43210, USA
3. Faculty of Biosciences, Norwegian University of Life Sciences, Aas 1432, Norway
4. Department of Microbiology, Radboud University, Nijmegen 6525, Netherlands
5. Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA