Microorganisms that metabolize natural gas such as propane inhabit natural gas fields.However, the amount of natural gas consumed by underground microbial activity and the conditions for storage without consumption were not well understood.

　Propane (C3H8) is a molecule in which three carbons are arranged in a straight line.Of these three, the research team separately measures the stable isotope ratios of the central carbon and the terminal carbon (elements with different mass numbers that exist stably without radiation decay), "intramolecular isotope distribution measurement". We developed a method called, and analyzed propane gas produced from gas fields in North America and Australia.

　As a result, in propane in some gas fields, the isotope ratio of the terminal carbon did not fluctuate much, but the isotope ratio of the central carbon showed a large fluctuation.This feature is inconsistent with the tendency of propane gas to be produced by pyrolysis.On the other hand, when a special microorganism that decomposes propane was cultivated in an oxygen-free environment and the isotope molecule of the remaining propane was measured, it was consistent with the tendency of this gas field.This is because anaerobic microorganisms consumed propane underground, and in some gas fields, more than half of the propane was eaten by the microorganisms.

　In the future, using the developed measurement method, it will be possible to predict the range of underground microbial activity, predict the amount of natural gas released into the atmosphere, which is also a greenhouse gas, and detect abiotic natural gas. ..It is said that it also has a spillover effect on research on the origin of life, in which organic matter that composes living things is created from inanimate objects.

Paper information:[Proceedings of the American Academy of Sciences] Intramolecular isotopic evidence for bacterial oxidation of propane in subsurface natural gas reservoirs