Maria Schindler, Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany, Susanne Liebner, GFZ German Research Centre for Geosciences, Section Geomicrobiology, Potsdam, Germany, Christian Knoblauch, University of Hamburg, Hamburg, Germany, Jens Strauss, Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research, Potsdam, Germany, Boris K Biskaborn, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany and Jens Kallmeyer, GFZ Potsdam, Geomicrobiology, Potsdam, Germany