Alexis Gilberta, et al., report that microbial anaerobic oxidation of hydrocarbons is a key process potentially involved in a myriad of geological and biochemical environments yet has remained notoriously difficult to identify and quantify in natural environments. The authors performed position specific carbon isotope analysis of propane from cracking and incubation experiments. Anaerobic bacterial oxidation of propane leads to a pronounced and previously unidentified 13C enrichment in the central position of propane, which contrasts with the isotope signature associated with the thermogenic process. This distinctive signature allows the detection and quantification of anaerobic oxidation of hydrocarbons in diverse natural gas reservoirs and suggests that this process may be more widespread than previously thought. Position-specific isotope analysis can elucidate the fate of natural gas hydrocarbons and provide insight into a major but previously cryptic process controlling the biogeochemical cycling of globally significant greenhouse gases.
The key result in this paper is the demonstration of the carbon isotopic enrichment trend for the central and terminal positions and the distinct differences in slope that can be used to identify the effects of AOH in an in situ real-world setting. Overall, anaerobic oxidation of propane leads to a trend that is reproducible between incubation experiments and natural environments, allowing the identification and quantification of AOH in natural environments. This study provides not only insight into hitherto
cryptic pathways in the hydrocarbon cycle but also an essential input for the development of global mass balance and flux models estimating the global significance of the process in natural environments.
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