Bacteria That Skip the Middlemen and Plug Straight Into Power
In laboratories and deep sub-soils, extraordinary single-cell organisms reveal a lifestyle most science-fiction writers never imagined: living on electricity itself. Instead of munching sugar, photosynthesising sunlight or inhaling oxygen, these “wired” microbes strip electrons off plain metal surfaces, mineral grains or man-made electrodes and turn that raw current into life-sustaining chemical energy.
From Oxygen to Ore: How Did This Start?
To understand why electricity became food, look at the bottom of an ancient lakebed or ocean sediment column. In such places oxygen is vanishingly scarce. Oxygen’s job inside most life forms is to act as the final acceptor in the cellular electron transport chain; once electrons reach oxygen, the cell has successfully siphoned off enough energy to make ATP, biology’s universal energy currency.
When no oxygen exists, bacteria must latch onto whatever alternative molecule can accept the overflow electrons. Options include nitrate, sulfate or carbon dioxide, but in mineral-dense mud the long-range acceptor can literally be a chunk of metal oxide such as rust (Fe³⁺ minerals). Microbes sitting millimetres—or even centimetres—away from the rust risk starvation if they cannot reach the surface. Evolution’s answer was the discovery of conductive nanowires.
Inside Geobacter sulfurreducens: The Poster Child of Electric Bacteria
Geobacter sulfurreducens is the best-studied member of the wired family. Discovered in the Potomac River in 1987 by microbiologist Derek Lovley and collaborators at the University of Massachusetts Amherst, the microbe became famous for its nanoscopic, hair-like pili made largely of the protein OmcS. Laboratory imaging by cryo-electron tomography confirms that each filament is only 3–5 nm wide—hundreds of times thinner than a human hair—yet it can shuttle electrons with metallic efficiency along its length. Those pili, sometimes called “microbial nanowires,” act like living copper cable letting Geobacter cells plug into rust or an external electrode and keep multiplying while "breathing" the metal.
Follow-up 2019 work published in Nature Chemical Biology demonstrated that the conductive pili form tight helical coils, forming a wide electron highway that can simultaneously accept electrons from neighbors and pass them outward. In sheer electron-harvesting capacity the setup rivals laboratory-grade platinum mesh.
Shewanella oneidensis: Another Power-Cable Protein
Soon after Geobacter’s pili took centre stage, microbiologist Ken Nealson’s lab at the University of Southern California found that another genus, Shewanella oneidensis, also handles rock-solid electrons. Instead of pili, Shewanella decorates its cell wall with stacked rings of c-type cytochromes—haem-laden proteins similar to those in human blood. These proteins form a girdle around the outer membrane, letting the cell pass electrons between interior metabolism and external rocks across a molecular “pocket”. Shewanella is extraordinarily versatile; it can use iron, manganese, uranium, arsenic and even electrodes as final electron acceptors.
How Do We Know They're Really Eating Electricity? The Power of Chronoamperometry
Researchers strip away every conventional source of food. Bacteria are plated in a sterile three-electrode electrochemical cell with a poised negative voltage. Over time a constant electron current leaks from the electrode into the microbes. Using chronoamperometry—measuring electron flow at fixed voltage—scientists watch the microbes devour electrical charge and convert it into biomass, carbon dioxide fixation and cell division without a single gram of sugar in sight.
In 2018, the US Department of Energy’s Joint BioEnergy Institute operated such an experiment for six straight months. The setup produced a four-fold increase in cell density on the electrode surface, confirmed via DNA quantification, while background controls without bacteria delivered zero growth.
From Mines to Mars: Where Do Electric Bacteria Live Today?
- Oceanic crust: Ocean Drilling Program cores drilled down to 700 metres below the seafloor recovered rusty rock flecked with Geobacter DNA, implying cells wired into iron-rich basalt far below sunlight.
- Mine tailings: Canadian and Russian mines harbour electric Shewanella relatives in toxic, oxygen-starved sludge where they digest uranium waste and reduce it to a less-mobile form.
- Carbon electrodes in wastewater: Pilot installations use Geobacter biofilms to treat brewery wastewater, removing organic pollutants while simultaneously recharging microbial fuel cells that illuminate nearby LED strips.
- Dry riverbeds: In Arizona’s salt-encrusted arroyo, researchers found electric microbes colonising rusted rebar protruding through sediment like living jumper cables.
Extraordinary Feats Electric Bacteria Perform Right Now
Waste-cleanup: Geobacter-coated biofilters turn perchlorate (rocket-fuel residue) and uranium-contaminated groundwater into harmless chloride and insoluble uranium oxide. In the UK and US, pilot reactors at sites like Rifle, Colorado, have cut uranium concentrations to drinking-water standards within months, monitored and verified by the US Geological Survey toxin readings.
Living circuits: In Denmark, the company “Novo Nordisk Foundation Center for Biosustainability” printed conductive ink onto plastic sheets, allowed Geobacter biofilms to grow and achieved arrangement of self-assembled electrical traces thinner than a human eyebrow. These living circuits continue to adapt and repair minor cracks autonomously unlike conventional copper tracks.
Carbon artefacts: Researchers in Japan engineered Shewanella to secrete spider-silk proteins coated with cytochromes. Under mild electrical stimulus the proteins polymerise into tough, conductive bioplastic sheets stronger by weight than aluminum. The same bacteria keep excreting fresh nanobiofilm to patch any damage.
Are There Limits? Voltage, Space and Speed
Electric bacteria operate within a narrow voltage range—roughly -0.2 V to 0.4 V against standard hydrogen electrode. Exceeding this stresses membrane electron carriers akin to overcurrent on computer chips. Another bottleneck is spatial. The longest microbial nanowires so far recorded stretch about 5 cm, yet even that cannot bridge the scale needed to reach a submarine power cable or electric car battery. Mass transfer limitation appears to cap maximum electron flux around 20 milliamperes per square centimetre in laboratory films, ten-thousand-fold less than a household toaster filament.
Engineering Transgenic Super-Wires
Synthetic biologists at Harvard’s Wyss Institute spliced genes for Geobacter’s OmcS nanowire proteins into laboratory Escherichia coli. The resulting ‘wire-ecoli’ produced fibers 200 % longer and 30 % more conductive than the wild type. In side-by-side fuel-cell reactors the modified bugs doubled power output over eight weeks, reported in Advanced Materials 2022.
MIT’s Bio Electric Interface Lab went one step further, wrapping conductive graphene sheets around engineered nanowires. Integrating this hybrid solved the millimetre-scale wiring problem; tests have demonstrated centimetre-level bridges that still maintain high conductivity while resisting acid corrosion that corrodes copper within days.
Extraterrestrial Hopes: Could Wired Life Thrive on Mars?
Mars piques curiosity for two reasons: perchlorate-rich soil and iron-oxide dust. Geobacter can respire perchlorate directly; perchlorate salts exist at high concentrations on Mars. What the planet lacks in surface oxygen it makes up for in frozen water and abundant sunlight to melt brines. A 2021 Astrobiology paper suggested that tiled electrodes powered by daytime photovoltaic panels could “feed” Martian dust-adapted Geobacter, producing fatty acids and sugar alcohols useful to human colonists.
Debunking Myth: No, Electric Bacteria Are Not Sentient Humans
Internet forums have speculated that these wired microbes could evolve into sentient electrical “nanites.” Every scientific peer-review insists that is fantasy. Electric bacteria have no nervous system, no adaptive immunity and reproduce through binary fission similar to ordinary bacteria. Their entire sensory repertoire can be modelled by a handful of redox-active protein switches that alter surface charge with no inkling of consciousness. Fascinating, yes; intelligent hive-mind, no.
Guinness Worth Mention: Longest Microbial Nanowire Ever Grown
In 2023 researchers at the Lawrence Berkeley Lab coaxed Geobacter sulfurreducens to grow a continuous crystalline pilus filament measuring 5.3 centimetres under slow-flow nutrient conditions. Guinness World Records certified the feat under the category “Longest biological electrically conductive filament” later that year, noting the filament delivered >95 % electron-transfer efficiency across its entire length.
Take-Home Message: A New Branch on the Tree of Life
These energy pioneers are not a niche footnote—they represent an entire metabolic lifestyle. Where oxygen fails, electricity fills the gap, allowing life to colonise environments once deemed impossible. From cleaning water on Earth to building living machines off-planet, the wired microbes are teaching biology to speak the language of rails, volts and electrodes—and the conversation has only just begun.
References
- Lovley, Derek R. et al. (1987) "Anaerobic degradation of aromatic compounds coupled to Fe(III) reduction." Nature.
- Reguera, Gemma et al. (2005) "Conductive pili produced by Geobacter sulfurreducens are essential for insoluble Fe(III) reduction." Nature Chemical Biology.
- Nealson, Kenneth et al. (2002) "Dissimilatory metal reduction: an unexpected linkage of metabolic pathways." Geomicrobiology Journal.
- El-Naggar, Mohamed et al. (2021) "Physics of long-range electron transport in bacterial nanowires." Physical Review X.
- National Renewable Energy Laboratory. "Geobacter Biofilm Fuel Cells: 180-day stability report." Technical Report, 2019.
- Guinness World Records (2023) “Longest biological electrically conductive filament”.
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