Humans have been getting microbes to do our bidding for millennia by taking their inherent processes (or engineered new processes) and applying them to making foods, drinks, drugs, biofuels, and other products. In most approaches, we feed them the right ingredients and wait for the good stuff to come out the other side. A study appearing in the latest issue of mBio reveals an electrifying new way to get what we want from bacteria: researchers manipulated bacterial metabolism by pulling excess electrons out of the mix and into an electrode.
Flynn et al. developed their system to coax an ethanol-making transformation out of Shewanella oneidensis. Using genes from Escherichia coli and Zymomonas mobilis, they created a custom plasmid that enabled S. oneidensis to convert glycerol to ethanol, but since the fermentation to ethanol is an unbalanced one, they needed to go one step further. By sticking an electrode into the reaction to draw off two electrons for every glycerol molecule, they were able to make the reaction favorable, thus making two valuable products in one step: ethanol and electricity.
“There’s been intense interest in microbe-electrode interactions for at least a decade now, and a lot of the interest has come from trying to produce electricity from waste organic matter,” says Derek Lovley, Distinguished Professor in the Department of Microbiology at the University of Massachusetts and a member of mBio’s Board of Editors. Lovley says the approach Flynn et al used is novel because instead of using the electrode solely for the purpose of generating electricity, they used it to coax a product out of the bacterium.
“This shows one of the alternatives – that you can use electrodes to manipulate microbial metabolism. It’s a proof of concept study, but it gives the idea that you could use the electrode to influence other complex fermentations,” says Lovley.
The authors assert that using electrode-interfaced bacteria expands the landscape of possibilities for metabolic engineering and synthetic biology strategies for producing biofuels and other materials.
Lovley agrees. “It was a very clever approach, and it helps open our eyes to how we might use microbes and electrodes for other practical applications,” he says.