The cable bacteria found in the Yarra river. Credit:Silvia Hidalgo Monash University biogeochemist Perran Cook said a patch of sediment the size of an adult footprint would host bacteria capable of generating one to two volts, enough for a small LED light. "It is extremely novel," Dr Cook said. "The whole idea of life conducting electricity in this way has only really been discovered in the last decade." Visible to the naked eye, the translucent bacteria grows insulated cables capable of conducting electricity over distances of several centimetres. "If you picked up some of this mud and cracked it open you would see tiny, thin hairs between the bits of mud," Dr Cook said.

The Yarra's "water layers" produced favourable conditions for the bacteria. The fresh water which flows from the catchments to the bay sits atop the salty water which flows upstream from the bay, as far up as Dights Falls. The freshwater layer serves as a lid, meaning that oxygen from the atmosphere can't get through to the lower layer. The low-oxygen levels boost hydrogen sulfide or rotten egg gas - the bacteria's food. "They get their energy from hydrogen sulfide, so the highest numbers (of bacteria) are where oxygen is at its lowest," Dr Cook said. The stretch of river between Scotch College, considered the epicentre, and Hawthorn Rowing Club was a classic area of low-oxygen. With one end buried in the sulphur-rich sediment and the other towards the surface of the mud, the bacteria is able to make a connection between its hydrogen sulfide food source found in the sediment and the oxygen it needs to survive - found on the surface of the mud.