Newly-Discovered Microbe Turns Oil into Methane

Methanoliparia, a species of archaea from deep-sea oil seeps of the Gulf of Mexico, splits long-chain hydrocarbons into methane and carbon dioxide, according to a new paper published in the journal mBio.

Methanoliparia is an important methanogenic alkane degrader in subsurface environments, producing methane by alkane disproportionation as a single organism. This image shows Methanoliparia cells attached to a droplet of oil. Scale bar - 10 μm. Image credit: Max Planck Institute for Marine Microbiology.

Methanoliparia is an important methanogenic alkane degrader in subsurface environments, producing methane by alkane disproportionation as a single organism. This image shows Methanoliparia cells attached to a droplet of oil. Scale bar – 10 μm. Image credit: Max Planck Institute for Marine Microbiology.

“Methanoliparia transforms hydrocarbons by a process called alkane disproportionation. It splits the oil into methane and carbon dioxide,” said lead author Dr. Rafael Laso-Pérez, a researcher at the Max-Planck Institute for Marine Microbiology and MARUM, and his colleagues.

“Previously, this transformation was thought to require a complex partnership between two kinds of organisms: archaea and bacteria.”

The scientists collected sediment samples from the Chapopote Knoll, an oil seep (about 10,000 feet, or 3,000 m, depth) in the Gulf of Mexico.

They carried out genomic analyses that revealed that Methanoliparia is equipped with novel enzymes to use the quite unreactive oil without having oxygen at hand.

“This is the first time we get to see a microbe that has the potential to degrade oil to methane all by itself,” Dr. Laso-Pérez said.

“The new organism, Methanoliparia, is kind of a composite being. Some of its relatives are multi-carbon hydrocarbon-degrading archaea, others are the long-known own methanogens that form methane as metabolic product,” added senior author Dr. Gunter Wegener, also from the Max-Planck Institute for Marine Microbiology and MARUM.

With the combined enzymatic tools of both relatives, Methanoliparia activates and degrades the oil but forms methane as final product.

“Microscopy shows that Methanoliparia cells attach to oil droplets. We did not find any hints that it requires bacteria or other archaea as partners,” Dr. Wegener said.

“We scanned DNA-libraries and found that Methanoliparia is frequently detected in oil reservoirs — and only in oil reservoirs — all over the oceans,” Dr. Laso-Pérez said.

“Thus, this organism could be a key agent in the transformation of long-chain hydrocarbons to methane.”

The team now plans to dig deeper into the secret life of this microbe.

“Now we have the genomic evidence and pictures about the wide distribution and surprising potential of Methanoliparia. But we can’t yet grow them in the lab. That will be the next step to take. It will enable us to investigate many more exciting details,” Dr. Wegener said.

“For example, whether it is possible to reverse the process, which would ultimately allow us to transform a greenhouse gas into fuel.”

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Rafael Laso-Pérez et al. 2019. Anaerobic Degradation of Non-Methane Alkanes by “Candidatus Methanoliparia” in Hydrocarbon Seeps of the Gulf of Mexico. mBio 10: e01814-19; doi: 10.1128/mBio.01814-19

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