Methane-eating bacteria discovery could help capture gas from the air

Copying the enzymes could let us harvest methane from the atmosphere.

Bacteria that convert methane in the air into useful products could be a vital tool for reducing our greenhouse gas emissions, if we can crack how they do it. A new discovery could kickstart efforts to engineer methane-harvesting bacteria, fight greenhouse emissions, and “mine” the air for useful compounds.

The problem with methane: Methane is an incredibly potent greenhouse gas. Compared with carbon dioxide (CO2), it is around 25 times more effective at trapping the sun’s heat inside Earth’s atmosphere.

Emitted by sources ranging from cattle and coal mines to pipelines and landfills, methane now makes up roughly 20% of all the greenhouse gases we emit – making it a key contributor to the warming climate. 

Methane is around 25 times more effective than CO2 at trapping the sun’s heat inside Earth’s atmosphere.

One potential solution involves capturing the methane we produce, and converting it into other chemicals. The key difficulty here is that the bonds within methane molecules are incredibly strong, making these chemical reactions difficult to control.

Yet nature has shown us that harvesting methane is possible. Each year, specialised bacteria named “methanotrophs” consume roughly 30 million tons of atmospheric methane, and convert it into less harmful compounds. In some cases, these can even be exploited for our benefit. 

The challenge: Already, researchers have begun to explore how methanotrophs could be used to convert atmospheric methane into compounds like methanol – potentially providing a cheap and abundant source of fuel. 

However, these efforts are currently limited by their low yields and inefficiency, preventing them from becoming competitive from an economic perspective. Researchers need to optimise the chemical reactions taking place within the bacteria, to maximise how much methane is being converted. 

That will require detailed knowledge of particular enzymes used by methanotrophs, named pMMO. These large, complex proteins are known to bind to methane at specific sites, and are crucial for catalysing the chemical reactions that convert methane. 

The team identified an as-yet undetected “binding site” on the enzyme.

The problem is that these enzymes are embedded within the delicate outer membranes of the bacteria. 

To study their structures on atomic scales, researchers so far have had to use damaging techniques to remove the enzymes from their hosts. When torn from its natural environment in this way, pMMO’s activity completely stops, making it virtually impossible for researchers to understand how it interacts with methane.

The study: A team led by Amy Rosenzweig at Northwestern University have now made an important step towards overcoming this problem. 

Their solution involves a more careful procedure, where the extracted enzymes are embedded into tiny nanodiscs of lipids – the same fatty molecules that comprise cell membranes. The idea was that the nanodiscs would resemble the enzymes’ native environment closely enough for the enzyme to keep reacting with methane. 

Researchers could engineer artificial enzymes that are better suited to converting atmospheric methane into useful products.

Using a 3D imaging technique named “electron cryotomography,” Rosenzweig’s team could closely study the behaviour of the enzymes, at a level of detail that allowed them to visualise the motions of individual atoms. The researchers discovered that, when embedded in the nanodiscs, the pMMO enzymes behaved completely differently from counterparts that had been removed from cell membranes entirely. 

Crucially, by interacting with the lipids surrounding them, these enzymes retained their ability to interact with methane molecules. For the first time, this allowed the team to identify an as-yet undetected “binding site” on the enzyme, where methane molecules likely undergo the reaction that converts them into methanol. 

Fine-tuned bioengineering: The team’s discovery could have far-reaching implications for our ability to capture methane directly from the atmosphere. Through an improved understanding of pMMO’s natural binding behaviour, researchers in future studies could engineer new, artificial enzymes based on pMMO. When embedded into the cell membranes of methanotrophs, these enzymes could be far better suited to converting atmospheric methane into useful products. 

By fine-tuning chemical reactions in this way, researchers could significantly boost the efficiency and yield of existing biomanufacturing processes, making them economically competitive. In turn, this could provide strong incentives for many industries to harvest the methane they produce at its source, rather than letting it go to waste — and heating up the atmosphere.

Rosenzweig’s team ultimately hope that their methods for observing methane-eating enzymes in their natural habitats will inspire a new wave of efforts to capture methane from the atmosphere directly – potentially helping to close the loop on our greenhouse gas emissions. 

We’d love to hear from you! If you have a comment about this article or if you have a tip for a future Freethink story, please email us at [email protected].

New material traps CO2 — and turns it into baking soda
A new material for direct air capture systems turns trapped carbon into baking soda when introduced to seawater.
“Zombie virus” revived after 48,500 years in permafrost
A newly discovered “zombie virus” was still able to infect hosts more than 48,500 years after it was trapped in Siberian permafrost.
Goodyear announces 90% sustainable tire
Made from a variety of recycled and repurposed materials, the tire may be perfectly suited for electric vehicles.
Startup plants first GMO trees designed for carbon removal
Living Carbon is ready to begin planting thousands of GMO trees engineered to pull 27% more carbon from the air.
This “chameleon” material can heat or cool houses on demand
Thanks to “electrochromism,” a newly developed material can switch between absorbing and reflecting heat from the sun.
Up Next
Subscribe to Freethink for more great stories