A news species of bacteria that forms itself into living electrical cables spanning several centimetres has been discovered in Danish mud.

The bacteria, a previously unknown member of the Desulfobulbaceae family, were found living in at the bottom of the bay of the Danish port, Aarhus, by Lars Peter Nielsen, a bioscientist at Aarhus University's Centre for Geomicrobiology. The discovery was confirmed by Christian Pfeffer, a student of Nielsen's.

Each individual bacteria cell consists of an insulating sheath surrounding a set of conducting fibres and measures one micrometre (a millionth of a metre) in length but the cells group together into far longer chains -- some several centimetres in length.

"To me, it's obvious that they are multicellular bacteria," says Nielsen. "This was a real surprise. It wasn't among any of our hypotheses. These distances are a couple of centimetres long -- we didn't imagine there would be one organism spanning the whole gap."

The reason for the bacteria to form such long structures appears to be one of energy production. The cells at the base of the chain are buried within the Aarhus bay's mud separating electrons from sulphides in the sediment and passing them to the cells at the top of the chain where they can combine with oxygen in the sea water. This electron transport chain generates energy for the bacteria.

Currently the evidence for the bacteria functioning as a living conductor is indirect. Nielsen was able to stop the cells carrying current out of the mud by short circuiting the system with tungsten wires and by placing filters in the sediment with pores too small to allow the bacteria to pass through but thus far direct measurement has been unsuccessful, possibly due to the cells' insulation.

As reported by Not Rocket Science, Nielsen is now curious to discover why, given their adaptation to low-oxygen conditions, the bacteria are not more prevalent.

"They seem to be the optimal organism in any place where you become short of oxygen," said Nielsen. "Why are they not everywhere? Or are they everywhere?"


  1. Truly Wired in mud.  

    Oct 25th 2012

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