Methane clathrate (white, ice-like material) under a rock from the seafloor of the northern Gulf of Mexico. Deposits such as these demonstrate that methane and other gases cross the seafloor and enter the ocean. Credit: NOAA
Key points:
- A research team discovered a new class of bacterial proteins that contribute to the formation and stability of methane clathrates, which trap methane gas beneath the seafloor.
- These proteins provide an eco-friendly and scalable way to suppress methane clathrate growth in offshore drilling pipelines as effectively as toxic chemicals.
- Understanding methane clathrate stability and formation provides insight into similar biomolecules that might sustain life beyond earth.
Methane clathrates, tiny cages of ice found along the coasts of continents, trap methane gas and prevent its entry into the atmosphere. A new study, published in PNAS Nexus, reveals a previously unknown class of bacterial proteins that contribute to the formation and stability of methane clathrates.
Researchers expected that seafloor clay-like sediment from the coast of Oregon would contain bacterial proteins resembling fish antifreeze proteins. They hypothesized that these proteins would influence methane clathrate growth, and identified their genes using a combination of DNA sequencing and bioinformatics.
The research team prepared various candidate proteins that could potentially bind to methane clathrates and tested their function and binding by forming clathrates in a unique chamber that replicated the high pressure and low temperature of the sea. This setup allowed them to measure how quickly and how much clathrate forms under both bacterial protein and protein-free conditions.
Researchers then performed molecular dynamic simulations to identify the site where the proteins attached to the methane clathrate. Surprisingly, the proteins did not bind to ice, but instead interacted with the clathrate structure to direct its growth. The portion of the protein resembling antifreeze proteins was buried within the structure and played a role in stabilization—rather than participating in clathrate binding as the team originally thought.
“Even though we chose these proteins based on their similarity to antifreeze proteins, they are completely different,” said study author Abigail Johnson of Georgia Tech. “They have a similar function in nature, but do so through a completely different biological system.”
These bacterial proteins can suppress methane accumulation in pipelines as effectively as toxic chemicals typically used in drilling, which can increase the environmental safety of transporting natural gas. Additionally, methane clathrates likely exist on the subsurface of Mars and on moons in the outer solar system. In the future, the research team hopes to determine if microbes exist in these locations and whether they produce similar biomolecules in the clathrate that could sustain life.