All life on Earth needs energy, but not all life eats food. Researchers at the University of Southern California discovered bacteria that subsist on a far simpler diet: pure electrons, harvested directly from solid metal surfaces.
These "electrotrophs" — including species of Geobacter and Shewanella — can be cultured on iron electrodes and grown by adjusting the voltage. They have specialized protein "wires" called pili that conduct electricity over distances of up to 100 times their body length.
Why This Matters
- They could be used to extract energy from polluted water
- They might form the basis of self-repairing biological batteries
- They could remediate radioactive waste, since some species "eat" uranium
- They challenge biology's definition of food and metabolism
The implications are profound: somewhere on the spectrum between plants (which photosynthesize) and animals (which eat), lies a third metabolic kingdom that simply connects to the grid.
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