Electricity-Generating Bacteria Cleans Wastewater

First located in New York’s Oneida Lake nearly 30 years ago, the bacterium Shewanella oneidensis is not only useful for cleaning water that contains mercury, lead, and iron. It can also generate electricity.

Researchers at the University of California, Santa Barbara have chemically modified the bacteria to increase its energy production capabilities, which could lead to another way for wastewater treatment plants to generate some of their own power.

Originally published in the journal Chem, the study shows that “Shewanella oneidensis features proteins in its cell membrane that conduct electrons and are essential for the cells' respiration.” In order to harness the ability of the bacterium's cells to produce energy as part of their metabolism, “the research team had to developed a synthetic molecule called DSFO+, which modifies these cell membranes but, since it contains iron, can still conduct electrons.”

The researchers created the iron-containing molecule DSFO+ with a structure that could mimic critical proteins in two mutant Shewanella bacteria. They worked toward determining whether incorporating DSFO+ would allow electron transfer in a manner similar to the protein's’ function.

When the scientists examined the effect of DSFO+ on the organism, they discovered that they could not only improve its capacity to produce electricity but also use the molecule to replace the function of the naturally occurring proteins in mutant bacteria. “Their enhancement resulted in the ability to change the behavior of microbial systems so that in the future such organisms could be used to treat wastewater through their electricity generation.”

By testing two mutant strains of Shewanella, the research team was able to discover that DSFO+ could not only replace the natural current-conducting proteins, “but do their job more efficiently, boosting the power that the microbe generated.”

"The protein replacement molecule that we constructed modifies the cell membrane so that it facilitates respiration by electron delivery to the membrane surface," Guillermo Bazan, co-author of the study, said. "It's a power-generating trick that gives us an opportunity to look into the behavior of microbial species in a way that didn't exist before."

Aside from being efficient at generating energy, the DSFO+ could also become a link between the electricity produced and the man-made systems that were able to handle the power.

The microbes could eventually be used to not just break down contaminants in wastewater, “but in the process generate enough electricity to recoup some of the cost of that water treatment.”