1. Laboratoire de Génétique des Prokaryotes, Université Libre de Bruxelles, IBMM, B-6041-Gosselies, Belgium1
2. Laboratory for Microbial Ecology and Technology, University of Gent, B-9000 Gent, Belgium2
3. Laboratory of Microbiology, Radioactive Waste & Clean-up Division, Center of Studies for Nuclear Energy, SCK/CEN, B-2400 Mol, Belgium4
4. Environmental Technology, Flemish Institute for Technological Research, VITO, B-2400 Mol, Belgium3