Deep microbes' key contribution to Earth's carbon cycle

This new finding, from the Tokyo Institute of Technology, highlights the importance of microorganisms in the geochemistry of natural gas and petroleum.

Hydrocarbons play key roles in atmospheric and biogeochemistry, the energy economy, and climate change. Most hydrocarbons form in anaerobic environments through high temperature or microbial decomposition of organic matter. Subsurface microorganisms can also 'eat' hydrocarbons, preventing them from reaching the atmosphere. Using a new technique, scientists show that biological hydrocarbon degradation gives a unique biological signature. These findings could help detect subsurface biology and understand the carbon cycle and its impact on climate.

The researchers fed propane to microorganisms in the lab to measure the specific 12C/13C signature produced these organisms, and measured the non-biological changes that occurred when propane is broken down at high temperatures, a process known as "cracking." They then used these baseline measurements to interpret natural gas samples from the US, Canada and Australia, allowing them to detect the presence of microorganisms using propane as "food" in natural gas reservoirs, and to quantify the amount of hydrocarbons eaten by microorganisms.

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When the researchers began analyzing samples from the bacterial simulation experiments, they matched perfectly what we observed in the field, suggesting the presence of propane degrading bacteria in the natural gas reservoirs.

Thus, this study revealed the presence of microorganisms that would have been difficult to detect using conventional methods, and opens a new window to understanding global hydrocarbon cycling.

Journal reference:

Intramolecular isotopic evidence for bacterial oxidation of propane in subsurface natural gas reservoirs. Proceedings of the National Academy of Sciences, 2019; 116 (14): 6653 DOI: 10.1073/pnas.1817784116

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology