Will Bacteria Replace Wires?

Tiny organisms found in soil may be the key to binding electronic devices with organic tissue.

It’s not surprising to hear that future pacemakers may be wireless. We’re living in an increasingly wireless world and even though pacemakers are devices many people rely on for survival, the idea that they’d carry electrical charge without wires probably won’t raise eyebrows. However, the notion that pacemakers may rely on bacteria found in dirt could be shocking.

Scientists have discovered how Geobacter sulfurreducens, bacteria that live in soil and sediment, can conduct electricity. Electricity travels in the bacteria through a seamless biological structure never before seen in nature. Scientists are now looking to co-opt that structure and use it to miniaturize electronics, create powerful-yet-tiny batteries, build pacemakers without wires and develop other medical advances.

Scientists have known that bacteria conducted electricity and believed they thought it did so through common, hair-like appendages called pili. But University of Virginia School of Medicine researcher Edward H. Egelman has found that the bacteria actually transmit electricity through immaculately ordered fibers made of an entirely different protein that surround a core of metal-containing molecules, much like an electric cord contains metal wires that’s 100,000 times smaller than the width of a human hair.

Now that they understand how the bacteria conduct electricity, researchers believe it could be used for bioenergy, cleaning up pollution and creating biological sensors. Moreover, the tiny organic nanowire could connect to tissue and bridge electronics and living cells for devices like pacemakers.

“This could lead to applications where you have miniature devices that are actually connected by these protein filaments,” Egelman said in a UVA release. “We can now imagine the miniaturization of many electronic devices generated by bacteria, which is pretty amazing.”

Geobacter bacteria play important roles in the soil, including facilitating mineral turnover and even cleaning up radioactive waste. They can survive without oxygen and use nanowires to rid themselves of excess electrons in a process that’s been likened to breathing. These nanowires have fascinated scientists, but it is only now that researchers at UVA, Yale and the University of California, Irvine, have learned how G. sulfurreducens uses these organic wires to transmit electricity.

“The technology [to understand nanowires] didn’t exist until about five years ago, when advances in cryo-electron microscopy allowed high resolution,” said Egelman. “We have one of these instruments here at UVA, and, therefore, the ability to actually understand at the atomic level the structure of these filaments.

Egelman said the discovery is just one of the mysteries they’ve solved with this technology, including a virus that can survive in boiling acid, and says there’ll be more to come.

Egelman hopes that further understanding of the natural world, including at the smallest scales, will provide scientists and manufacturers with valuable insights and useful ideas.

“One example that comes to mind is spider silk, which is made from proteins just like these nanowires, but is stronger than steel,” he said. “Over billions of years of evolution, nature has evolved materials that have extraordinary qualities, and we want to take advantage of that.”