1. Department of Environmental Microbiology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland;
2. School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, Oregon;
3. Department of Environmental Social Sciences, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland;
4. Department of Biological Sciences, University of Zimbabwe, Harare, Zimbabwe