Bacteria Power

By Jade Boyd

The U.S. Air Force has long been interested in microscale air vehicles—some as small as insects—to serve as spy drones, but it has been stymied by the lack of a suitable, compact power source. But a diverse team of researchers from Rice and the University of Southern California (USC) thinks it has discovered a power source small enough: bacteria.

Andreas Lüttge.

Rice geochemist Andreas Lüttge will spearhead the team of microbiologists, engineers, and geochemists as they join forces to create bacteria fuel cells that could power palm-size spy drones and other electronic devices. Fueled by a $4.4 million grant from the Department of Defense’s Multidisciplinary University Research Initiative, the Rice–USC research team hopes to prove its concept valid within five years by producing a self-propelled prototype.

The key is understanding how the bacteria Shewanella oneidensis attach to and interact with anode surfaces inside the fuel cell. Anodes are the parts of fuel cells and batteries that gather excess electrons for harvesting. To optimize its design, the team must understand how bacteria transfer electrons to anode surfaces under a variety of conditions.

“There are three primary components in the system: the bacteria, the surface, and the solution that the bacteria are digesting,” says Lüttge. “Any change in one variable will affect the other two, and what we want to do is find out how to tweak each one to optimize the performance of the whole system.”

Lüttge’s participation in the program grew out of a decade-long collaboration with principal investigator Kenneth Nealson, a USC professor who helped pioneer the field of modern geobiology and the investigation of the genetic pathways that some microbes rely on to maintain their respiratory metabolism in oxygen-poor environments. Shewanella oneidensis uses metals instead of oxygen to fully metabolize its food.

“Since this organism is capable of passing electrons directly to solid metal oxides,” Nealson explains, “it is not particularly surprising that it can do the same to the anode of the fuel cell. It seems a reasonable step to apply the same approaches to understanding current production. What is new here is the incorporation of colleagues in chemistry, geology, engineering, and evolutionary biology to optimize the entire system, not just the bacteria.”

The researchers still have a lot to learn about the chemical cues that the Shewanella use—both individually and in colonies—but they are incredibly efficient at converting organic inputs to electricity. “We are confident,” Lüttge says, “that they’ll be great candidates for our fuel cells.”