Newly discovered microbe degrades oil to gas

Crude oil and gas naturally escape from the seabed in many places known as "seeps." There, these hydrocarbons move up from source rocks through fractures and sediments towards the surface, where they leak out of the ground and sustain a diversity of densely populated habitats in the dark ocean. A large part of the hydrocarbons, primarily alkanes, is already degraded before it reaches the sediment surface. Even deep down in the sediment, where no oxygen exists, it provides an important energy source for subsurface microorganisms, amongst them some of the so-called archaea.

These archaea were good for many surprises in recent years. Now a study led by scientists from the Max Planck Institute for Marine Microbiology in Bremen, Germany, and the MARUM, Centre for Marine Environmental Sciences, provides environmental information, genomes and first images of a microbe that has the potential to transform long-chain hydrocarbons to methane. Their results are published in the journal mBio.

Splitting oil into methane and carbon dioxide

This microbe, an archaeon named Methanoliparia, transforms the hydrocarbons by a process called alkane disproportionation: It splits the oil into methane (CH4) and carbon dioxide (CO2). Previously, this transformation was thought to require a complex partnership between two kinds of organisms, archaea and bacteria. Here the team from Max Planck Institute for Marine Microbiology and MARUM presents evidence for a different solution.

During a cruise in the Gulf of Mexico, the scientists collected sediment samples from the Chapopote Knoll, an oil and gas seep, 3000 m deep in the ocean. Back in the lab in Bremen, 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.

With the combined enzymatic tools of both relatives, Methanoliparia activates and degrades the oil but forms methane as final product. Moreover, the visualization of the organisms supports the proposed mechanism: Microscopy shows that Methanoliparia cells attach to oil droplets.

Methanogenic microorganisms have been important for the earth's climate through time as their metabolic product, methane, is an important greenhouse gas that is 25 times more potent than carbon dioxide.

See:

Rafael Laso-Pérez, Cedric Hahn, Daan M. van Vliet, Halina E. Tegetmeyer, Florence Schubotz, Nadine T. Smit, Thomas Pape, Heiko Sahling, Gerhard Bohrmann, Antje Boetius, Katrin Knittel, Gunter Wegener. Anaerobic Degradation of Non-Methane Alkanes by “Candidatus Methanoliparia” in Hydrocarbon Seeps of the Gulf of Mexico. mBio, 2019; 10 (4) DOI: 10.1128/mBio.01814-19

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology