What a Shocker—These Microbes Breathe Electricity

The Flash can generate electricity, but can he breathe it? Surprisingly, there is a creature that can do both, and it is not some fabricated metahuman; it’s a bacterium.

Geobacter, colloquially referred to as “electricigens,” is a genus of bacteria that dwells in oxygen-deprived environments deep beneath the ocean floor. Researchers have uncovered two extraordinary abilities of the bacteria since it was first discovered in 1987: bioremediation, the ability to degrade pollutants into non-toxic material, and electrogenesis, the ability to generate electricity.

Like humans, Geobacter microbes produce waste electrons during respiration, the process in which food is converted to usable energy. Unlike humans, who rely on oxygen to remove leftover electrons, the bacteria produce nanowires and exhale the electrons to distances thousands of times their body length, generating an electric current in the process. These electrons are typically passed into iron oxide, a compound found in minerals in soil. Microbes extract energy from iron oxide minerals to power their activities. Until recently, the nanowires produced were assumed to be pili, appendages commonly found on the surface of bacteria. However, in a 2019 study, researchers discovered that the nanowires are made of cytochromes, proteins that transfer electrons in metabolic pathways. They also found that pili beneath the cell membrane function as an on-off switch that controls the extrusion of the nanowires.

The bacteria’s ability to thrive in hypoxic, or oxygen-deprived environments, may deem it effective in treating bacterial infections. Harmful bacteria like Salmonella are able to outcompete probiotics in the gut since they can continue to produce energy without the presence of oxygen. Though this proposal is still in its infancy, scientists believe that probiotics that are equipped with nanowires like Geobacter may be able to outcompete pathogens like Salmonella, which can then prevent infection.

Since Geobacter obtains electrons from organic matter, scientists also speculate that the bacteria may drive the future of recyclable energy by powering devices using waste as their primary food source. In a recent study, Geobacter bacteria were also found to be resistant to cobalt, a metal used in batteries that is extremely toxic to living organisms. When exposed, the bacteria coat themselves with cobalt nanoparticles through the efflux pump CzcABC, which removes toxic substances to maintain a stable internal environment. This forms a protective shield and prevents the cobalt from permeating the membrane. As a result, Geobacter may soon be used to extract cobalt from discarded batteries for reuse, reducing metal waste sent to landfills and preventing toxic materials within batteries from contaminating the environment.

In addition to recycling waste, Geobacter are able to clean up radioactive waste through bioremediation. Accordingly, many scientists have used Geobacter to clean up uranium waste and even extract it from water. Though this ability was discovered by Dr. Gemma Reguera and her team nearly 20 years ago, it was not until recently that they learned the mechanics of it.

Geobacter also produce protein filaments, or long chains of protein, to zap waste, trapping it in a mineral form and immobilizing it. As a result, the waste cannot spread through the environment or dissolve in water. However, this did not account for the removal of the waste. Reguera found that the bacteria coat themselves in lipopolysaccharides, or molecules of fats and carbohydrates, to soak up the waste like a sponge. Similar to its role in activating the cytochromes, the pili control the production and expression of the lipopolysaccharides. As a result, instead of killing the bacteria, absorbing the toxic uranium provides the bacteria with energy, prompting scientists to investigate what other toxic metals the bacteria can remove from the environment, specifically cadmium.

As time has progressed, Geobacter microbes have only opened doors to more possibilities and applications. Solely by performing their basic metabolic activities, they can become a valuable, sustainable, and efficient source of energy. They are also invulnerable to metals that are typically a death sentence for bacteria, allowing them to prevent and clean up waste while fueling themselves. Due to their numerous abilities, these bacteria may soon form the basis of revolutionizing the production of energy, recycling materials, and freeing the environment of toxins.