A study shows how microbes that consume electricity use electrons to repair carbon dioxide

A new research from Washington University in St. Louis explains the cellular processes that allow a sun-loving microbe to "eat" electricity, that is, to transfer electrons to fix the carbon dioxide to fuel its growth.

Led by Arpita Bose, badistant professor of biology of arts and sciences, and Michael Guzman, Ph.D. candidate in her lab, a team from the University of Washington showed how a strain of Rhodopseudomonas palustris absorbs electrons from conductive substances such as metal oxides or rust. The work is described in a March 22 article in the newspaper Nature Communications.

The study builds on Bose's earlier finding that R. palustris TIE-1 can consume electrons from rust inhibitors, such as suspended electrodes, a process called extracellular electron absorption. R. palustris is phototrophic, which means that it uses the energy of light to perform certain metabolic processes. The new research explains the cell wells where this microbe discharges the electrons that it eats electricity.

"This clearly shows for the first time that this activity – the body's ability to eat electricity – is linked to the fixation of carbon dioxide," said Bose, a Packard Fellow who studies the microbial metabolisms and their influence on the biogeochemical cycle.

This mechanical knowledge can help guide efforts to harness the microbe's natural ability to store energy sustainably or other applications of bioenergy, a potential that has attracted attention. of the Ministry of Energy and the Department of Defense.

"R. palustris Strains can be found in wild and exotic locations, such as a rusty bridge at Woods Hole, Mbadachusetts, where TIE-1 was isolated, "said Bose. Really, you can find these organisms everywhere. This suggests that the extracellular absorption of electrons could be very common. "

Guzman added, "The main challenge is that it's an anaerobic bacterium, so you have to grow it in an oxygen-free environment in order to capture the light energy." But the other side of the coin is that these challenges are met with a lot of versatility in this body that many other agencies do not have. "

In their new article, the researchers showed that electrons of electricity enter the membrane proteins that are important for photosynthesis. Surprisingly, when they removed the ability of the microbe to repair carbon dioxide, they found a 90% reduction in its ability to consume electricity.

"He really wants to fix carbon dioxide using this system," said Bose. "If you take away that innate ability, she just will not take electrons."

She said the reaction is similar in some respects to a rechargeable battery.

"The microbe uses electricity to recharge its redox pool, storing electrons and reducing it dramatically," Bose said. "To unload it, the cell reduces carbon dioxide.The energy needed for all this comes from sunlight.The whole process is repeated, allowing the cell to make biomolecules with nothing more than electricity, carbon dioxide and the sun. "

A Washington-based university team overcame a number of technical hurdles to complete this study. Mark Meacham of the McKelvey School of Engineering has contributed to the design and fabrication of microfluidic devices that allow researchers to focus on activities in cells, such as bacteria powered by electricity sources. The team also relied on the support of collaborators, including David Fike from the Department of Earth and Planet Sciences, who helped Bose and Guzman use secondary ion mbad spectrometry to determine how the microbe uses carbon dioxide.

The new research answers fundamental scientific questions and offers many opportunities for future applications of bioenergy.

"For a long time, people knew that microbes could interact with electrode badogues in the environment, that is, with minerals also charged," Guzman said. "But no one really understood how photoautotrophs could do this, like those types of organisms that fix their own carbon and use light to produce energy.This research fills a gap that is poorly understood in the field."

Bose's lab is working on the use of these microbes to make bioplastics and biofuels.

"We hope this ability to combine electricity and light to reduce carbon dioxide can be used to help find sustainable solutions to the energy crisis," Bose said.

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More information:
Nature Communications (2019). DOI: 10.1038 / s41467-019-09377