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Wired Bacteria Form Nature's Power Grid: 'We Have an Electric Planet'

Electroactive bacteria were unknown to science until a couple of decades ago. But now that scientists know what to look for, they're finding this natural electricity across much of the world, even on the ocean floor. It alters entire ecosystems, and may help control the chemistry of the Earth. "Not to sound too crazy, but we have an electric planet," said John Stolz, a microbiologist at Duquesne University in Pittsburgh.

In the mid-1980s, Dr. Stolz was helping to study a baffling microbe fished out of the Potomac River by his colleague Derek Lovley. The microbe, Geobacter metallireducens, had a bizarre metabolism. "It took me six months to figure out how to grow it in the lab," said Dr. Lovley, now a microbiologist at the University of Massachusetts at Amherst.

[...] In the early 2000s, a Danish microbiologist named Lars Peter Nielsen discovered a very different way to build a microbial wire. He dug up some mud from the Bay of Aarhus and brought it to his lab. Putting probes in the mud, he observed the chemical reactions carried out by its microbes.

[...] Each wire runs vertically up through the mud, measuring up to two inches in length. And each one is made up of thousands of cells stacked on top of each other like a tower of coins. The cells build a protein sleeve around themselves that conducts electricity.

As the bacteria at the bottom break down hydrogen sulfide, they release electrons, which flow upward along the "cable bacteria" to the surface. There, other bacteria — the same kind as on the bottom, but employing a different metabolic reaction — use the electrons to combine oxygen and hydrogen and make water.

Cable bacteria are not unique to Aarhus, it turns out. Dr. Nielsen and other researchers have found them — at least six species [open, DOI: 10.1016/j.syapm.2016.05.006] [DX] so far — in many places around the world, including tidal pools, mud flats, fjords, salt marshes, mangroves and sea grass beds.

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