1. 2Laboratory of Microbiology, Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium
2. 1Centre for Rhizobium Studies, Murdoch University, Western Australia, Australia
3. 3Faculty of Agriculture and Life Sciences, Lincoln University, Lincoln, New Zealand
4. 4The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK