TY - JOUR A1 - Rasesh, Pokharel A1 - Gerrits, Ruben A1 - Schuessler, Jan A. A1 - Floor, Geerke H. A1 - Gorbushina, Anna A1 - von Blanckenburg, Friedhelm T1 - Mg isotope fractionation during uptake by a rock-inhabiting, model microcolonial fungus Knufia petricola at acidic and neutral pH N2 - The model rock-inhabiting microcolonial fungus Knufia petricola fractionates stable Mg isotopes in a time and pH-dependent manner. During growth, the increase of 26Mg/24Mg in the fungal cells relative to the growth media amounted to 0.65 ± 0.14‰at pH 6 and 1.11 ± 0.35‰at pH 3. We suggest a constant equilibrium fractionation factor during incorporation of Mg into ribosomes and ATP as a cause of enrichment of 26Mg in the cells. We suggest too that the proton gradient across the cell wall and cytoplasmic Membrane controls Mg2+ transport into the fungal cell. As the strength of this gradient is a function of extracellular solution pH, the pHdependence on Mg isotope fractionation is thus due to differences in fungal cell mass fluxes. Through a mass balance model we show that Mg uptake into the fungal cell is not associated with a unique Mg isotope fractionation factor. This Mg isotope fractionation dependence on pH might also be observed in any organism with cells that follow similar Mg uptake and metabolic pathways and serves to reveal Mg cycling in ecosystems. KW - Isotope fractionation KW - Fungus KW - Magnesium PY - 2017 U6 - https://doi.org/10.1021/acs.est.7b01798 SN - 0013-936X SN - 1520-5851 VL - 51 IS - 17 SP - 9691 EP - 9699 PB - ACS Publications CY - USA AN - OPUS4-43018 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -