Deep Microbes Shed Light On Carbon Cycle

Scientists have discovered a way to track the activity of microbes that degrade hydrocarbons, which could lead to a better understanding of the Earth’s carbon cycle.

AsianScientist (Apr. 17, 2019) – In a study published in the Proceedings of the National Academy of Sciences, an international team of scientists has developed a technique to identify hydrocarbon degradation by biological systems. Their findings could help in detecting subsurface biology and understanding the carbon cycle.

Hydrocarbons play key roles in atmospheric- and biogeo-chemistry, the energy economy and climate change. Most hydrocarbons form in oxygen-poor, or anaerobic, environments through high temperature or microbial decomposition of organic matter. Microorganisms can also ‘eat’ hydrocarbons underground, preventing those hydrocarbons from reaching the atmosphere.

To detect and measure the activities of these microorganisms, researchers led by Professors Alexis Gilbert, Naohiro Yoshida and Yuichiro Ueno at the Tokyo Institute of Technology, Japan, developed a method involving the measurement of position-specific stable carbon isotope ratios.

Hydrocarbons are mostly long chains of carbon atoms attached to hydrogen atoms, but carbon has two naturally abundant isotopes: carbon-12 (12C) and carbon-13 (13C). Depending on how organisms form environmental hydrocarbons, the ratio of 12C/13C for each specific carbon atom position in a hydrocarbon can be unique.

In this study, the researchers chose to focus on propane, a natural gas hydrocarbon molecule containing three carbon atoms. They fed propane to microorganisms in the lab to measure the specific 12C/13C signature produced by these organisms, and measured the non-biological changes that occurred when propane is broken down at high temperatures, a process known as cracking.

The team 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.

“When I started 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,” Gilbert noted.

This study also has important implications for global climate change as propane and other hydrocarbons are greenhouse gases and pollutants, said the researchers. Gilbert added that in the future, his team’s approach may be useful for detecting life on extraterrestrial bodies such as other planets or moons in our solar system.

The article can be found at: Gilbert et al. (2019) Intramolecular Isotopic Evidence for Bacterial Oxidation of Propane in Subsurface Natural Gas Reservoirs.


Source: Tokyo Institute of Technology; Photo: Shutterstock.
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