Prof. Dr. Shuhei Ono 

Isotopologue fractionation by cultures performing anaerobic oxidation of methane under high pressure

Methane is both an important energy source and a strong greenhouse gas. Understanding the sources of methane and ist emission rates to the environment is essential in securing the transitional energy resource and designing the mitigation strategy for climate change. Methane comes in different isotope configurations called isotopologues. Our laboratory has developed a novel spectroscopy technique to measure doubly isotope-substituted isotopologues (13CH3D and 12CH2D2) to gain new insights into the biogeochemical cycles of methane in the environment. Studies so far have shown that isotopologue ratios of methane from deep marine sediments can tell the temperature of methane generation or consumption and indicates in-situ microbe cycling of methane. However, laboratory cultures of methanogenic and methanotrophic microbes have not reproduced signals observed in natural environments. During my sabbatical at the HWK, I propose to collaborate with Drs. Kai-Uwe Hinrichs and Gunter Wegener in MARUM and MPI in Bremen to investigate the methane isotopologue exchange catalyzed by laboratory cultures performing anaerobic oxidation of methane. High-pressure (50 to 100 bars) culturing will better reproduce the natural geochemical conditions of marine sediments and is expected to promote a high rate of methane activation. The knowledge gained by this project will be used to estimate the geographical distributions of microbes in deep marine sediments.