Herman P. van Leeuwen is an electrochemist who obtained his degree in chemistry at the State University of Utrecht, The Netherlands, in 1969. His thesis was in the field of pulse methods in electrode kinetics, and his Ph.D. degree was awarded cum laude (best 5% in The Netherlands) in 1972. He then joined the Colloid Chemistry and Electrochemistry group of Professor J. Lyklema at Wageningen University, where he became a senior lecturer in 1986. His teaching includes analytical/ inorganic chemistry, electrochemistry and environmental physical chemistry. He was appointed Extraordinary Professor at the University of Geneva in 2000. His current major research interests are twofold: (1) ion dynamics and electrokinetics of colloids, and (2) dynamic speciation and bioavailability of metals in environmental systems. He has published some 140 research papers, reviews and book chapters in these fields. He was chairman of the IUPAC Commission on Fundamental Environmental Chemistry from 1995 to 1999, and Chairman of the Electrochemistry Section of the Royal Dutch Chemical Society from 1993 to 2001. Together with J. Buffle, he edits the IUPAC Book Series on Analytical and Physical Chemistry of Environmental Systems, launched in 1992.

Wolfgang Köster studied biology at the Universities of Bielefeld and Tu¨bingen, Germany. Placing emphasis on biochemistry, plant physiology, genetics and microbiology he was influenced by the work of Professor V. Braun, Professor E. Sander and Professor H. Zähner. In 1986, he earned his Ph.D. from the University of Tübingen. With a grant from the German Science Foundation (DFG), in 1988 he became a post-doctoral fellow in the laboratory of Professor R. J. Kadner at the School of Medicine, University of Virginia, USA. He was then promoted to a position equivalent to Assistant Professor and the 'Habilitation' in Microbiology at the University of Tübingen. Between 1998 and 1999 he held the position of 'Visiting Scientist' (Cantarini Fellowship of the Institut Pasteur and Fellowship of the Centre National de la Recherche Scientific (CNRS), France) in the laboratory of Professor M. Hofnung, Institut Pasteur, Paris, France. In 1999, he joined as a Senior Scientist (leading the group Drinking Water Microbiology) the Swiss Federal Institute for Environmental Science and Technology (EAWAG). He gained teaching experience from the Universities of Tübingen and Hohenheim and ETH Zürich by conducting lectures, seminars and practical courses at undergraduate and graduate levels in the areas of microbiology, genetics, biochemistry, molecular biology and environmental science. His major areas of work and interest comprise: (1) survival strategies and molecular detection methods for bacteria in drinking water and environmental habitats, (2) membrane-associated transport phenomena in microbes, with focus on metal transport in bacteria, and (3) bioavailability and ecotoxicity of metals and hydrophobic organic compounds in green algae.