Outer membranes of Geobacter sulfurreducens incorporate electron-conducting protein filaments that transfer electrons generated by the digestion of food inside the cell to iron atoms outside the cell.
Waste-to-energy operations, where organic waste materials are burned to generate steam to produce electricity, are not uncommon in many cities around the world. Lowly, single-celled organisms are teaching us how to improve that process by leaps and bounds. Certain species of bacteria in the Geobacter genus are capable of “eating” organic material, but rather than using oxygen to soak up electrons generated in the process, like most creatures do, these bacteria pass these electrons on to iron atoms – the same type of iron atoms present in rust. More importantly, transferring these electrons from inside the cell, where the consumption of the organic material takes place, to insoluble electron receptors outside the cell requires overcoming the insulating oily cell membrane. Geobacter performs the task by incorporating conducting proteins (c-type cytochromes) within the cell membrane and periplasm to shuttle electrons to the exterior. Conductive filaments called pili extend from the outside of the cell and facilitate the transfer of electrons to the iron atoms.
