Washington University scientists are studying a type of bacteria with an ancient way of powering itself that could help counteract the very modern problem of climate change.
The microbes, known as photoferrotrophs, steal electricity from iron. Like plants, they need sunlight to grow — and in the process, suck up climate-warming carbon dioxide.
Though they’ve thrived in our oceans for more than 2 billion years, these microscopic creatures were thought to be relatively rare.
But new research from Washington University suggests these microbes could be common in aquatic environments. Found in wetlands from Missouri to Massachusetts, the bacteria could be absorbing carbon dioxide on a large scale, scientists say, underscoring the importance of conserving these threatened habitats.
Even within the scientific community, these microbes are often considered an oddity, said Wash U microbiologist Arpita Bose.
“For a long time, people have thought these are exotic organisms, something that isn’t important anymore,” Bose said. It doesn’t help, she added, that the microbes are notoriously difficult to keep alive in the lab.
The testing of these microbes by Bose and her students began by chance in 2015, when she decided to bring home a few glass vials of ocean-dwelling bacteria to her lab in landlocked Missouri.
The samples — a “rainbow” of electric green, pink and orange bacteria — came from a wetland near Woods Hole Oceanographic Institution in Cape Cod, Mass. She passed them off to her students, including Dinesh Gupta and Michael Guzman, who slowly isolated the different species.
“Studying these microbes is challenging,” said Guzman, now a postdoctoral researcher at Lawrence Livermore Laboratory. “They grow without oxygen, so you have to make sure the environment is oxygen-free, and they’re typically slower-growing.”
On a whim, the team decided to test the microbes to see if they were capable of growing with only iron and sunlight. Bose still remembers the day her students burst into her office to share their results: All 15 strains were photoferrotrophs.
“I was kind of shocked,” she said. “Not in our wildest imagination would we have thought these would all be photoferrotrophs. It takes these serendipitous discoveries to put these kinds of organisms in the limelight. You’re like, ‘Wait a minute, this actually could be a game-changer.’”
It’s more than just scientific curiosity that’s pushing Bose and her colleagues to better understand these microbes.
As they grow, aquatic bacteria like photoferrotrophs are vacuuming up carbon dioxide, a key greenhouse gas driving climate change. If these microbes are widespread in shallow, iron-rich waters, they could be absorbing climate-warming gases on a massive scale, Bose explained.
“There are all of these invisible microorganisms that are doing big jobs for us and they’re just not getting noticed,” she said. “I think the microbial contribution to carbon sequestration in wetlands is going to be a very key component that we should discuss as part of our plan for climate change.”
Preserving these ecosystems, and the bacteria that live there, will likely play an important role in combating climate change — and not just in coastal areas.
Days before the pandemic began, Bose and her students collected samples from a protected wetland in West Alton, Missouri, and found similar types of bacteria. “Wherever we’re sampling, we’re finding these organisms,” she said. “That makes me think that this is something that’s important that we really need to understand.”
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