The world's deep seafloors are dark and airless places, but vast swaths may pulse gently with energy conducted through a type of newly discovered bacteria that forms living electrical cables. The bacteria were first detected in 2010 by researchers perplexed at chemical fluctuations in sediments from the bottom of Aarhus Bay in Denmark. Almost instantaneously linking changing oxygen levels in water with reactions in mud nearly an inch below, the fluctuations occurred too fast to be explained by chemistry. Only an electrical signal made sense -- but no known bacteria could transmit electricity across such comparatively vast distances. Were bacteria the size of humans, the signals would be making a journey 12 miles long. Now the mysterious bacteria have been identified. They belong to a microbial family called Desulfobulbaceae, though they share just 92 percent of their genes with any previously known member of that family. They deserve to be considered a new genus, the study of which could open a new scientific frontier for understanding the interface of biology, geology and chemistry across the undersea world. The bacteria are described Oct. 24 in Nature by researchers led by microbiologists Christian Pfeffer, Nils Risgaard-Petersen and Lars Peter Nielsen of Aarhus University. On the following pages, Wired takes a look at these marvelous microbes. Above: Microbial Wires Seen through an electron microscope, the Desulfobulbaceae -- the researchers haven't yet given them a genus or species name -- appear in blue. They link end-to-end, forming filaments nearly an inch in length. Image: Nils Risgaard-Petersen

Wiring Diagram In the photo above, orange strands of the new Desulfobulbaceae stretch in a laboratory beaker between a reddish, oxygen-rich sediment layer and a dark, sulfurous, oxygen-depleted layer. This is the essential structure of much of the world's seafloor, and one that the new Desulfobulbaceae evolved to exploit: One end feeds on hydrogen sulfide below, pulling out an electron that's sent up the chain and, at the other end, is used to pull in oxygen. (See diagram below.) It's a simple form of breathing. Water is generated as a byproduct. Images: 1) Nils Risgaard-Petersen 2) Nature

Live Wire The new Desulfobulbaceae, seen in cross-section above, has a shape seemingly adapted to conducting electricity. Down each bacterium run deep channels, which are aligned continuously as the bacteria join into one long filament. It's through these channels that electrons likely course. (This is still speculation, albeit informed -- the bacteria clearly transfer electrons, but the exact route hasn't been mapped.) The walls of the channels and a surrounding membrane may have insulating properties, like sheathing around a wire. Image: Karen E. Thomsen

A Single Organism Each filament of the new Desulfobulbaceae doesn't merely represent the end-to-end alignment of many individual microbes, but should be a considered a single multicellular organism, said Nielsen. Image: Mingdong Dong

Electric Ecology In just one teaspoon of mud, the researchers found a full half-mile of Desulfobulbaceae cable, and it's not just a Danish phenomenon. Nielsen said other researchers have sent him samples from seafloors around the world, including Tokyo Bay. It's possible that, at the microbial level, the deep seafloor is humming with current. With so much electricity being transferred, are other organisms tapping the lines? Might the Desulfobulbaceae be a power source for entire as-yet-unappreciated deep-sea microbial ecologies, which in turn shape some of the planet's fundamental biogeochemical processes? That's "an interesting possibility," said Nielsen, but it's still speculation. Less speculatively, the Desulfobulbaceae are definitely breaking down iron sulfides and carbonates in deeper sediment, while generating iron oxide and magnesium calcite at the surface, Nielsen said. The latter are important compounds for life in the oceans above, and ultimately on land. If the new Desulfobulbaceae are as widespread and populous as they seem, they could be an important component of life's deep-time cycles. Image: Nils Risgaard-Petersen