Bacteria are one of the most diverse and adaptable organisms on Earth. They can even be found in harsh environments where few other creatures can survive. There are some species of bacteria that eat and breathe electricity. It sounds a bit like science fiction, but it’s another example of how microorganisms can adapt to a wide range of extreme environments, using whatever resources are available for energy and as nutrients, unlike any other life-form on Earth. These extraordinary bacteria use naked electricity; they eat and breathe electrons. Aren’t they fascinating? They often live in muddy sea beds or along the banks of rivers. Finding them is easy; biologists can coax them out of hiding by sticking an electrode in the sediment bed. The bacteria nearest to the electrodes even grow the biological equivalent of electrical wires out of their bodies so that other microbes further away can hook up to the electricity source. It is effectively a living wire. Back in 1987 Derek Lovely and his lab associates at the University of Massachusetts first came across these bacteria on the banks of the Potomac River, Washington DC. [1] These microbes, called Geobacter metallireducens, were getting their electrons from organic compounds and passing them onto iron oxides. In other words, they were eating waste including ethanol, and effectively “breathing” iron instead of oxygen. Of course, this is not breathing as far as we know it. For one thing, bacteria do not have lungs. Instead, the bacteria pass their electrons to metal oxides that lie outside the cell. They do this through special hair-like wires that protrude from the cell’s surface. These tiny wires act in much in the same way that copper wire does when it conducts electricity. They have been dubbed “microbial nanowires”. Geobacter bacteria are able to survive on energy sources entirely unavailable to most lifeforms. In 1988, a year after Lovley’s discovery, microbiologist Kenneth Nealson of the University of Southern California found another one. He was investigating a strange phenomenon in Oneida Lake in New York State. The lake contains manganese, which reacts with the oxygen in the air to form manganese oxide. However, Nealson did not find as much manganese oxide as he was expecting. Some of it was missing. The culprit, as it turns out, was Shewanella oneidensis. This bacterium breathes oxygen when it is available, but in the muddy banks of the lake where oxygen is scarce, it instead passes its electrons directly onto manganese oxide, producing a stream of electricity. It can also do the same thing with other metals like iron. Under the microscope, Shewanella appears to have long thin hair-like extensions on its outer membrane. These filaments were at first thought to conduct electrons along with them like a copper cable, much like Geobacter. However, it turns out that the long filaments are only conductive when dried out in a lab. Instead, Shewanella appears to shuttle electrons out of its cells using transport molecules called flavins and “stepping stone” proteins embedded in the outer membrane called cytochrome.

Furthermore, in August 2018, scientists have made successful isolation of bacteria that can eat and breathe electricity from hot springs in the Yellowstone National Park. [2] They used electrodes that are inserted into the water to capture them. They heat-loving bacteria that breathe electricity can live in extreme environments such as an alkaline hot spring where the temperatures ranged from 43-930C. Such discoveries are of prime significance as these microbes can be a potential solution for cleaning up environmental pollution while generating sustainable energy two major challenges humanity is facing. These bacteria can eat toxic pollutants and pass electrons into metals or other solid surfaces, thus generating a stream of electricity enough to run various low power applications.

[1] Lovley RD et al., Anaerobic production of magnetite by a dissimilatory iron-reducing microorganism. (1987), Nature, 330: 252–254

[2] Abdelrhman Mohamed, et al., In situ enrichment of microbial communities on polarized electrodes deployed in alkaline hot springs. Journal of Power Sources, 2019; 414: