1. Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, 8092 Zürich, Switzerland.
2. Division of Microbial Ecology, Department of Microbiology and Ecosystem Science, Research Network “Chemistry Meets Biology”, University of Vienna, Vienna 1090, Austria.
3. Large-Instrument Facility for Advanced Isotope Research, University of Vienna, Vienna 1090, Austria.
4. Environmental Biochemistry Group; Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), 8600 Dübendorf, Switzerland.