In the oxygen-starved crevices of the world—gut linings, deep-sea vents, wastewater pipes—some bacteria are doing something totally out of the ordinary. Instead of inhaling oxygen like we do, they’re pushing electrons out of their cells, generating electricity in the process. Now, scientists have uncovered the precise mechanism behind this microbial magic trick—and it might just change the future of clean energy.
Researchers at Rice University, working with colleagues at the University of California, San Diego, have discovered how certain bacteria can “breathe” by releasing electrons onto external surfaces. This process, known as extracellular respiration, has puzzled scientists for decades. But in a study published in Cell, the team revealed how common bacteria like Escherichia coli pull off this electric feat.
“This newly discovered mechanism of respiration is a simple and ingenious way to get the job done,” said Biki Bapi Kundu, a Rice doctoral student and first author of the study. “Naphthoquinones act like molecular couriers, carrying electrons out of the cell so the bacteria can break down food and generate energy.”
A Different Kind of Breath
Breathing, at its core, is about moving electrons. In humans and most other organisms, oxygen acts as the final destination for those electrons, helping release energy stored in food. But life evolved long before Earth had much oxygen in its atmosphere. Bacteria had to find another way.
What Kundu and his colleagues showed is that E. coli, a model organism found in our guts and lab flasks around the world, can survive without oxygen by using a small molecule—2-hydroxy-1,4-naphthoquinone (HNQ)—to ferry electrons from inside the cell to the outside. This process is mediated by two enzymes: NfsB and NfsA, part of a class known as nitroreductases. Together, they enable what scientists call mediated extracellular electron transfer, or EET.
The electrons then move onto conductive surfaces—essentially turning the bacteria into living batteries.
“[It] solves a long-standing scientific mystery,” said Caroline Ajo-Franklin, a professor of biosciences at Rice and senior author of the study. “But it also points to a new and potentially widespread survival strategy in nature.”
Batteries With DNA
The team also ran computer simulations, in collaboration with Bernhard Palsson’s lab at UC San Diego, modeling how bacteria would grow in an oxygen-free world laced with electrodes. The simulations held up in real-world experiments: bacteria placed on conductive materials continued to thrive, discharging electrons as they went.
Even more intriguing, the bacteria adapted quickly. After short-term exposure to electrode surfaces, E. coli developed a specific mutation in a gene called OmpC, which encodes a protein in the outer membrane. This mutation helped the bacteria grow even better on the anode.
In other words, not only can these bacteria breathe electricity—they evolve to do it more efficiently.
Petri Dish Powerhouse
This discovery carries weight far beyond academic curiosity. Bacteria that exhale electricity could become vital tools in biotechnology and energy systems.
“Our work lays the foundation for harnessing carbon dioxide through renewable electricity, where bacteria function similarly to plants with sunlight in photosynthesis,” said Ajo-Franklin.
Such bacterial systems could improve wastewater treatment, help stabilize imbalanced industrial fermentations, or even enable bio-electronic sensors in extreme environments, from deep mines to outer space. In anaerobic zones where traditional sensors fail, electricity-breathing microbes could act as real-time signalers of chemical change.
The implications are especially exciting for carbon capture. If engineered properly, these microbes could one day help convert carbon dioxide into useful fuels or compounds—powered by electricity from renewable sources.
Rethinking the Microbial World
For decades, extracellular respiration has been something of a scientific black box. Researchers could see the effects—currents on electrodes, persistent bacterial growth—but not the internal wiring. Now, that mystery is beginning to unravel.
What’s especially striking is the simplicity of the solution. Instead of building complex protein chains like those found in mitochondria, these bacteria rely on small molecules and common enzymes. That simplicity, researchers say, suggests that this form of respiration might be far more widespread in nature than anyone suspected.
And E. coli—long the workhorse of molecular biology—might be just the beginning.
In a world increasingly shaped by the twin crises of energy demand and climate change, it may turn out that some of our most unlikely allies are already here—quietly exhaling electrons in the dark.
