1. Environmental Microbiology Laboratory (EML), Ecole Polytechnique Federale de Lausanne (EPFL), EPFL-ENAC-IIE-EML, Station 6, CH-1015 Lausanne, Switzerland
2. Department of Chemistry, University of Oslo, P.O. Box 1033, NO-0315 Oslo, Norway
3. Environmental Biogeochemistry and Ecotoxicology, Department F.-A. Forel for Environmental and Aquatic Sciences, School of Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, Uni Carl Vogt, Bvd Carl-Vogt 66, CH-1211 Geneva 4, Switzerland