For the first two billion years of Earth history, microbial life and our planet coevolved under an anoxic atmosphere. Today, microbial communities abound in anoxic environments — like the continental and marine subsurfaces — where they actively cycle carbon and nutrients. These facts demonstrate that sustainable biospheres do not require molecular oxygen to thrive. Indeed, our best hopes for finding life beyond Earth likely lie with planets and moons that may be anoxic as well. Despite the importance of anaerobic microorganisms to planetary evolution and astrobiology, there are major open questions surrounding their influence on Earth’s carbon cycle. My research program focuses on the rates, mechanisms and limitations of anaerobic organic degradation, which is a key component of global carbon dynamics. Central in this process are organic acids (e.g. acetate), small molecule intermediates generated as organic matter is broken down into greenhouse gases. Organic acids are rapidly turned over by microbial metabolisms and abiotic reactions alike. By combining method development, metabolic modeling and experimental geobiology, I harness organic acids as a window into the carbon cycle, informing both our understanding of anoxic microbial ecology and the potential for life elsewhere in the Solar System. In this seminar, I will present new Orbitrap mass spectrometry techniques that I have developed to measure precise isotope ratios of organic acids with unprecedented sensitivity. I will demonstrate how the isotopic signatures of organic acids identify their metabolic origins and quantify their in situ turnover rates. These analyses offer unique insights into the microbial activity of anoxic subsurface ecosystems and valuable applications to astrobiology research.

*Refreshments: 10:30 AM - 11:00 AM (ES&T L1175)