1. Institute of Life Sciences, Université catholique de Louvain, Croix du Sud, 1, bte L7.04.01, B-1348 Louvain-la-Neuve, Belgium
2. Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, box 2460, B-3001 Leuven, Belgium
3. Department of Bioscience Engineering, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium
4. Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland, P.O. Box 66, FIN-00014 Helsinki, Finland