Sea bed wired up with thousands of kilometres of living electrical cables made of bacteria, says new study

Just a teaspoon of mud can contain a kilometre of living electric cables

Scientists believe they are the source of electric currents on the sea bed



Living electric cables made from bacteria have been discovered on the sea bed.

The weird multi-cellular microbes are one centimetre long and a hundred times thinner than a human hair.

Each one functions as an electric cable containing a bundle of insulated wires - similar to the cables that run power to electric lights and appliances.

Scientists believe they are the source of mysterious electric currents on the ocean floor, identified for the first time nearly three years ago.

The will to survive: In just a teaspoonful of mud at the bottom of the ocean there may be a kilometre of living electric cables, according to the latest research

The cable bacteria, from the family Desulfobulbaceae, generate electricity by consuming oxygen from seawater. This is used to power a process that releases energy from sulphur in mud on the sea bed.

Tens of thousands of kilometres of cable bacteria can live under a single square metre of the ocean floor, say the researchers, whose find is reported in the journal Nature.

They appear to consist of single cells and provide energy by linking the oxygen reservoir at the surface of the mud with hydrogen sulphide deep below.

The 'cable' bacteria: Each one contains a bundle of insulated wires - similar to the cables that run power to electric lights and appliances

Lead scientist Dr Nils Risgaard-Petersen, from Aarhus University in Denmark, said: 'The incredible idea that these bacteria should be electric cables really fell into place when, inside the bacteria, we saw wire-like strings enclosed by a membrane.'

The cables can stretch to around a centimetre in length, connecting the deepest bacteria living in low oxygen conditions with those in high oxygen areas.

A cubic centimetre of sediment can contain up to a kilometre of compacted cable with the bacterial colony monopolising sulphide oxidation in the soil, preventing other microbes from using the resource.

Microbial ecologist Dr Risgaard-Petersen, of Aarhus University, Denmark, said: 'On the one hand, it is still very unreal and fantastic. On the other hand, it is also very tangible.'



He added: 'They abounded in sediment zones with electric currents and along their length they contained strings with distinct properties in accordance with a function as electron transporters.'

The finding could lead to the creation of medical devices that mimic the electron transmission, and using the bacteria to clean up contaminated areas.

Dr Risgaard-Petersen added: 'Living, electrical cables add a new dimension to the understanding of interactions in nature and may find use in technology development.'

Tiny: A cubic centimetre of sediment can contain up to a kilometre of compacted cable with the bacterial colony monopolising sulphide oxidation in the soil, preventing other microbes from using the resource

Professor Gemma Reguera, a microbiologist at Michigan State University reviewed the research for the journal.

She said: 'A few years ago, any suggestion microbes could function as power cables to transmit electric currents across centimetre distances would have been met with scepticism.

'The authors provide compelling evidence linking the presence of long filaments of a previously unknown group of bacteria to the electric currents that couple spatially separated geochemical reactions in marine sediments.'

She said the report adds to a growing body of evidence highlighting the crucial role microbial electron transfer has in global geochemical processes and in the functioning of ecosystems.