1. Department of Microbiology, Faculty of Agriculture and Forestry; University of Helsinki; PO Box 56 FI-00014 Finland
2. Molecular and Integrative Biosciences Research Programme, Faculty of Biological and Environmental Sciences; University of Helsinki; PO Box 56 FI-00014 Finland
3. Institute of Biotechnology; University of Helsinki; PO Box 65 FI-00014 Finland