1. Department of Microbiology, University of Bergen, Jahnebakken 5, P.O. Box 7800, N-5020 Bergen, Norway, Center of Marine Biotechnology, University of Maryland Biotechnology Institute, East Pratt Street, Baltimore, Maryland 21202, School of Science and Technology, Stavanger University College, P.O. Box 8002, N-4068 Stavanger, Norway, and Centre of Molecular Biology and Neuroscience and Institute of Medical Microbiology, University of Oslo, National Hospital, N-0027 Oslo, Norway