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upstart writes in with an IRC submission for nutherguy:

'Electric mud' teems with new, mysterious bacteria:

For Lars Peter Nielsen, it all began with the mysterious disappearance of hydrogen sulfide. The microbiologist had collected black, stinky mud from the bottom of Aarhus Harbor in Denmark, dropped it into big glass beakers, and inserted custom microsensors that detected changes in the mud's chemistry. At the start of the experiment, the muck was saturated with hydrogen sulfide—the source of the sediment's stink and color. But 30 days later, one band of mud had become paler, suggesting some hydrogen sulphide had gone missing. Eventually, the microsensors indicated that all of the compound had disappeared. Given what scientists knew about the biogeochemistry of mud, recalls Nielsen, who works at Aarhus University, "This didn't make sense at all."

The first explanation, he says, was that the sensors were wrong. But the cause turned out to be far stranger: bacteria that join cells end to end to build electrical cables able to carry current up to 5 centimeters [~2 inches] through mud. The adaptation, never seen before in a microbe, allows these so-called cable bacteria to overcome a major challenge facing many organisms that live in mud: a lack of oxygen. Its absence would normally keep bacteria from metabolizing compounds, such as hydrogen sulfide, as food. But the cables, by linking the microbes to sediments richer in oxygen, allow them to carry out the reaction long distance.

When Nielsen first described the discovery in 2009, colleagues were skeptical.

[...] But the more researchers have looked for "electrified" mud, the more they have found it, in both saltwater and fresh. They have also identified a second kind of mud-loving electric microbe: nanowire bacteria, individual cells that grow protein structures capable of moving electrons over shorter distances. These nanowire microbes live seemingly everywhere—including in the human mouth.

[Ed note: The story provides an outstanding example of the scientific method at work: hypothesize, test, examine results, and repeat as needed. Well worth reading.]

Original Submission