The bacteria that can capture carbon

With global greenhouse gas emissions reaching an all-time high last year, many scientists and world leaders are now arguing that new technologies which can capture carbon and store it underground are needed to help the world meet its climate goals.

And some believe that nature could provide a powerful solution. Microbes – the miniscule organisms that are found all around us but are invisible to the naked eye – play a vital role in capturing carbon and affecting the climate. Plus they could also be harnessed to tackle other environmental problems – such as the drastic fall in pollinator populations.

Scientists have recently discovered a microbe, a type of cyanobacteria, off the coast of a volcanic island near Sicily that eats carbon dioxide (CO2) "astonishingly quickly".

The island of Vulcano is surrounded by underwater hydrothermal vents, which are rich sources of CO2. These vents are located in shallow water, which means they are exposed to sunlight (unlike vents in the deep ocean). All this has created the perfect environment for the evolution of microbes that use CO2 as a food source.

The microbes found here in September 2022 are "hyper-efficient at consuming CO2 through photosynthesis", says Braden Tierney, a data scientist focusing on microbiology at Weill Cornell Medical College and Harvard Medical School, and executive director of the Two Frontiers Project, which led the research. The project was funded by US biotechnology company Seed Health, which employs Tierney as a consultant.

Together with a team of researchers from Harvard and Cornell universities in the US and the University of Palermo in Sicily, and with help from the Vulcano community, Tierney isolated a microbe that converted CO2 into biomass faster than other known cyanobacteria. A study outlining the results will be published later this year.

Scientists discovered a type of cyanobacteria that eats CO2 "astonishingly quickly" off the coast of a volcanic island near Sicily (Credit Getty Images)

Cyanobacteria are a type of bacteria that use photosynthesis to obtain energy, capturing carbon in the process, and the new strain is "one of the fastest growing cyanobacteria… ever reported", says Tierney. He describes cyanobacteria as "nature's little alchemists" as they absorb large amounts of CO2 and can convert it into useful resources, such as fuels or biodegradable plastics.

"Early data showed [this new strain] generated 22% more biomass than the other fastest growing strains out there," says Tierney. As it grows denser and heavier, the microbe sinks in the water, which helps it sequester the CO2 it absorbs, he says.

The carbon capture potential of cyanobacteria is already widely studied. What makes this discovery "truly remarkable" is the fact that the cyanobacteria strain can absorb CO2 at such a rapid rate, says Helen Onyeaka, an industrial microbiologist and associate professor at the University of Birmingham in the UK.

"While rapid CO2-consuming microbes have been researched, this particular strain's absorption rate seems unparalleled," she says.

A "living database"

This year, Tierney and his team have also travelled to the Rocky Mountains in Colorado in search of more carbon-gobbling microbes. The region is "a hotbed of activity for carbonated springs" and dissolved CO2 concentrations are up to a thousand times higher than Sicily's volcanic seeps, according to the researchers. Tierney says they isolated microbe strains here with "much higher CO2 levels than what we actually saw in Sicily".

The team is creating a "living database" which will be available to other scientists worldwide, allowing them to pair DNA sequences with the banked bacteria samples and thus continue studying the microbes long after expeditions.

Tierney says the findings from Vulcano "are expanding our view of billions of years of evolution". Because of microbes' ability to adapt to different environmental conditions and planetary changes, he feels "confident that in those evolutionary processes lie the tools we need to address [climate change]".

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Scientists say that tackling climate change will require large-scale carbon capture, which could potentially be achieved via new technology or through protecting and enhancing existing natural ecosystems such as forests, peatlands and soils. Last year the UN's Intergovernmental Panel on Climate Change (IPCC) said that carbon capture is essential because even big cuts to emissions won't be enough to limit global warming. Although some scientists warn that it could provide governments and industry with an unwarranted excuse to avoid the stringent emissions cuts that are needed to tackle climate change.

Tierney says microbial solutions should be harnessed to "work in concert" with other technologies and natural systems to suck CO2 out of the atmosphere.

Using microbes, such as cyanobacteria and microalgae, for deliberate carbon capture "can be very promising", says Kira Schipper, a researcher at the Center for Sustainable Development at Qatar University. They grow much faster than conventional crops, which means they capture more carbon in the same time-frame, she adds.

Another benefit is that biomass produced by microbes "can be grown on non-arable land, and in seawater, thereby not competing with food production", she says. The biomass can be grown in large ponds or bioreactors and used for biofuels, fertilisers, protein supplements and animal feed.

Braden Tierney and his team discovered a microbe that generates 22% more biomass than other fast-growing cyanobacteria strains (Credit: Seed Health / John Kowitz)

Using microbes to capture carbon is more cost-effective than harnessing technologies such as direct air capture, says Onyeaka.

"Microbial processes generally have low operational costs compared to technological interventions for carbon capture, which can often be capital-intensive," she says. They are also "inherently scalable" as microbes "can be deployed in diverse environments, from open ponds to bioreactors", she adds.

But technological constraints make scaling up these kinds of systems difficult, says Schipper. "Best-practices to select top strains, to cultivate them at large scale, including maximising the amount of CO2 that is absorbed, and then to harvest the biomass, are challenging and vary drastically between strains and locations." Some companies have already started implementing systems to capture CO2 using microbes. In the US, LanzaTech uses bacteria to convert CO2 into aviation fuels and chemicals used in products ranging from laundry detergents to perfumes. UK company CyanoCapture is using cyanobacteria to produce biological oils and biomass.

Medicinal microbes

Microbes could also have a multitude of other environmental benefits besides their carbon capture potential. According to a recent Canadian study, for example, they could help revive dying honeybee populations.

Pollinator populations are steadily declining worldwide, and the US saw its highest ever yearly loss rate for honey bee colonies between 2020 and 2021. (Read more: Can we save the bees that feed the world?)

Microbiologist Brendan Daisley from the University of Guelph in Canada set out to combat this "insect apocalypse" by developing probiotics that boost the health of bees.

Just like humans, bees have a microbiome and a healthy balance of microbes in their gut is essential for their overall health. Studies show that pesticides and antibiotics are harming the microbiota of bees, impacting their health.

This is also affecting crop production and food supply, warns Daisley. "It is a cascading effect," he says. According to a 2020 study, a lack of bees is already limiting the supply of certain crops, including apples, blueberries and cherries, in 13 US states.

By targeting hives with probiotics, the scientists aimed "to re-establish microbial balance in honeybees," says Daisley, who is a scientific fellow at Seed Health. Alongside a team of researchers from Western University and Lawson Health Research Institute in Canada, he delivered three probiotic strains to more than 30 large commercial hives in California, using a spray and a pollen patty infusion.

Both methods were shown to be highly effective at warding off bacterial and fungal pathogens.

The probiotics also increased the growth of the targeted hives, says Daisley.

Partnering with Seed Health, the scientists are now developing patents for the strains.

Scientists have shown that probiotics can ward off pathogens in honeybee hives (Credit: Getty Images)

Onyeaka warns, however, that while scientific developments such as trialing these honey bee probiotics and the cyanobacteria discovered in Vulcano are promising, it is important to proceed cautiously.

Introducing microbes to the environment in large quantities could disrupt local ecosystems, while carbon storage may not be permanent, she says. "When the microbes die, there's potential for the carbon to be released back into the environment unless further steps are taken."

"Before scaling up the use of any microbial solutions, it's imperative to understand any potential environmental repercussions. We need to ensure the cure isn't worse than the ailment," she adds.

Still, scientists are hopeful that microbes can help make our planet healthier and more sustainable.

"Compared to other [carbon capture] solutions, microbes are infinitely replicable," says Tierney. "While there is no silver bullet for tackling climate change, it is really exciting to find an organism that is a really high performing engine for carbon capture."

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