1. Department of Biotechnology, University of Turku, Tykistökatu 6A, FIN-20520 Turku, Finland; Department of Biology, Åbo Akademi University, Artillerigatan 6, FIN-20520 Åbo, Finland; and EELA, National Veterinary and Food Research Institute, Hämeentie 57, FIN-00580 Helsinki, Finland