It's electrifying: bacteria, it seems, can share energy simply through touch.
In a lab in Massachusetts, researchers have evolved a very unusual colony of symbiotic bacteria. The bacteria, which belong to two different species, cannot live without each other and grow biological wires to share energy in the form of electrons.
"They can just wire themselves up to each other," says Derek Lovley, a microbiologist at the University of Massachusetts at Amherst. "I think it's probably one of the most surprising things I've seen working in microbiology."
Lovley and his team grew two strains of geobacter bacteria that needed each other to grow. Geobacter metallireducens breaks down ethanol to get energy, but can only do so if it has somewhere to dump spare electrons. Geobacter sulfurreducens can't break down ethanol but can accept electrons.
So Lovley and his colleague Zarath Summers put them together, started nine co-cultures, and waited. They expected the two species to team up and completely break down the ethanol, and that G. metallireducens would pass the spare electrons to G. sulfurreducens using hydrogen as a chemical shuttle.
Initially, the marriage went poorly and the bacteria consumed very little ethanol. But after several months, something strange happened. Red clumps formed in the liquid cultures. The bacteria had mutated and were now producing cytochrome, a red protein.
Cytochrome conducts electricity and is known to line fine hairs called "nanowires" that are produced by both bacteria.