From seafloor to space: New bacterial proteins shine light on climate and astrobiology

Gigatons of greenhouse gasoline are trapped below the seafloor, and that is an excellent factor. Across the coasts of the continents, the place slopes sink down into the ocean, tiny cages of ice entice methane gasoline, stopping it from escaping and effervescent up into the environment.

Whereas not often within the information, these ice cage formations, generally known as methane clathrates, have garnered consideration due to their potential to have an effect on local weather change. Throughout offshore drilling, methane ice can get caught in pipes, inflicting them to freeze and burst. The 2010 Deepwater Horizon oil spill is assumed to have been attributable to a buildup of methane clathrates.

However till now, the biological process behind how methane gasoline stays secure below the ocean has been nearly fully unknown. In a breakthrough research, a cross-disciplinary staff of Georgia Tech researchers found a beforehand unknown class of bacterial proteins that play an important function within the formation and stability of methane clathrates.

A staff led by Jennifer Glass, affiliate professor within the College of Earth and Atmospheric Sciences, and Raquel Lieberman, professor and Sepcic-Pfeil Chair within the College of Chemistry and Biochemistry, confirmed that these novel bacterial proteins suppress the expansion of methane clathrates as successfully as industrial chemical substances at the moment utilized in drilling, however are non-toxic, eco-friendly, and scalable. Their research informs the seek for life within the solar system, and will additionally enhance the protection of transporting natural gas.

The analysis, published in the journal PNAS Nexus, underscores the significance of basic science in finding out Earth’s pure organic methods and highlights the advantages of collaboration throughout disciplines.

“We needed to know how these formations have been staying secure below the seafloor, and exactly what mechanisms have been contributing to their stability,” Glass stated. “That is one thing nobody has finished earlier than.”

Sifting by sediment

The hassle began with the staff analyzing a pattern of clay-like sediment that Glass acquired from the seafloor off the coast of Oregon.

Glass hypothesized that the sediment would include proteins that affect the expansion of methane clathrate, and that these proteins would resemble well-known antifreeze proteins in fish, which assist them survive in chilly environments.

However to verify her speculation, Glass and her analysis staff would first should establish protein candidates out of thousands and thousands of potential targets contained within the sediment. They’d then must make the proteins within the lab, although there was no understanding of how these proteins would possibly behave. Additionally, nobody had labored with these proteins earlier than.

Glass approached Lieberman, whose lab research the structure of proteins. Step one was to make use of DNA sequencing paired with bioinformatics to establish the genes of the proteins contained within the sediment. Dustin Huard, a researcher in Lieberman’s lab and first writer of the paper, then ready candidate proteins that would doubtlessly bind to the methane clathrates. Huard used X-ray crystallography to find out the construction of the proteins.

Creating seafloor situations within the lab

Huard handed off the protein candidates to Abigail Johnson, a former Ph.D. pupil in Glass’ lab and co-first writer on the paper, who’s now a postdoctoral researcher on the College of Georgia. To check the proteins, Johnson shaped methane clathrates herself by recreating the high pressure and low temperature of the seafloor within the lab. Johnson labored with Sheng Dai, an affiliate professor within the College of Civil and Environmental Engineering, to construct a singular strain chamber from scratch.

Johnson positioned the proteins within the strain vessel and adjusted the system to imitate the strain and temperature situations required for clathrate formation. By pressurizing the vessel with methane, Johnson compelled methane into the droplet, which prompted a methane clathrate construction to type.

She then measured the quantity of gasoline that was consumed by the clathrate—an indicator of how rapidly and the way a lot clathrate shaped—and did so within the presence of the proteins versus no proteins. Johnson discovered that with the clathrate-binding proteins, much less gasoline was consumed, and the clathrates melted at larger temperatures.

As soon as the staff validated that the proteins have an effect on the formation and stability of methane clathrates, they used Huard’s protein crystal construction to hold out molecular dynamics simulations with the assistance of James (JC) Gumbart, professor within the College of Physics. The simulations allowed the staff to establish the particular website the place the protein binds to the methane clathrate.

A surprisingly novel system

The research unveiled surprising insights into the construction and performance of the proteins. The researchers initially thought the a part of the protein that was much like fish antifreeze proteins would play a task in clathrate binding. Surprisingly, that a part of the protein didn’t play a task, and a completely totally different mechanism directed the interactions.

They discovered that the proteins don’t bind to ice, however reasonably work together with the clathrate construction itself, directing its development. Particularly, the a part of the protein that had comparable traits to antifreeze proteins was buried within the protein construction, and as a substitute performed a task in stabilizing the protein.

The researchers discovered that the proteins carried out higher at modifying methane clathrate than any of the antifreeze proteins that had been examined up to now. Additionally they carried out simply in addition to, if not higher than, the poisonous industrial clathrate inhibitors at the moment utilized in drilling that pose severe environmental threats.

Stopping clathrate formation in pure gasoline pipelines is a billion-dollar business. If these biodegradable proteins could possibly be used to forestall disastrous pure gasoline leaks, it might significantly scale back the danger of environmental injury.

“We have been so fortunate that this truly labored, as a result of although we selected these proteins based mostly on their similarity to antifreeze proteins, they’re fully totally different,” Johnson stated. “They’ve an identical perform in nature, however achieve this by a totally totally different organic system, and I believe that actually excites individuals.”

Methane clathrates probably exist all through the solar system—on the subsurface of Mars, for instance, and on icy moons within the outer solar system, comparable to Europa. The staff’s findings point out that if microbes exist on different planetary our bodies, they may produce comparable biomolecules to retain liquid water in channels within the clathrate that would maintain life.

“We’re nonetheless studying a lot in regards to the primary methods on our planet,” Huard stated. “That is one of many nice issues about Georgia Tech—totally different communities can come collectively to do actually cool, surprising science. I by no means thought I might be engaged on an astrobiology mission, however right here we’re, and we have been very profitable.”