1. UFZ—Helmholtz Centre for Environmental Research, Department
of Isotope Biogeochemistry, Permoserstraße 15, 04318 Leipzig, Germany
2. University of Freiburg, Faculty of Biology, Schaenzlestraße 1, 79104 Freiburg, Germany
3. MPI—Max Planck Institute for Marine Microbiology, Department of Microbiology, Celsiusstrasse 1, 28359 Bremen, Germany