1. Molecular Biotechnology, Institute of Biology, Leiden University; Sylviusweg 72 Leiden 2333BE The Netherlands
2. Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology; Karl-von-Frisch-Strasse 10 Marburg 35043 Germany
3. InBioS, Centre for Protein Engineering; University of Liège; Liège B-4000 Belgium
4. Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW); Droevendaalsesteeg 10 Wageningen 6708 PB The Netherlands