Enter bacteria. A species known as Shewanella oneidensis, to be precise.
These microorganisms can survive and thrive in both aerobic and anaerobic conditions with or without oxygen. Not only that, but the microbes employ electrons in their metabolism, using energy to make essential precursors for anchoring carbon molecules, a process during which organisms take carbon from carbon dioxide and add it to an organic molecule.
Scientists are working towards artificially engineering a new bacteria that goes a step further by using those precursor molecules to make organic molecules such as biofuels.
A team of scientists at Cornell University in the United States have designed a method that facilitates the uptake of electrons into microbial metabolism for the synthesis of complex energy-dense organic molecules from CO2 and renewable electricity. Even a few microbes can perform the task effectively.
“There are only a very small number of microbes that can really store renewable electricity,” explains Buz Barstow, assistant professor of biological and environmental engineering in the College of Agriculture and Life Sciences who was a key member of the research team.
Optimising corn to get more biofuel out
By examining the genes of the bacteria by help of a technique they call “knockout sudoku,” Barstow and his colleagues inactivated genes one by one to see what functions they each serves.
“We found a lot of genes that we already knew about for getting electrons out of the cell are also involved in getting electrons in,” Barstow said. “Then we also found this totally new set of genes that nobody’s ever seen before that are needed to get electrons into the cell.”
Earlier research has shown that these bacteria can serve as “living electrodes.” Other scientists have stressed the allure of this microbe owing to “its extraordinary prospects for energy production, pollution treatment, and biosynthesis.”
Before life on Earth developed photosynthesis, the first bacteria likely used a pathway similar to that found in Shewanella oneidensis for harnessing electrons from oxidizing iron to pull carbon from carbon dioxide for use in making sugars, Barstow and his colleagues speculate.
The pathway that the microbes employ for converting CO2 into sugars and biofuels is highly efficient, they explain. It could easily be scaled up and would be inexpensive to operate.
“When we build a microbe that can eat electrons, which we are doing now, it will incorporate those genes,” said Barstow, who wants to start adding the genes extracted from Shewanella to Escherichia coli, a bacteria commonly used in laboratory experiments.
Engineered bacteria powered by electrons could pave the way for using renewable energy for making biofuels, food and chemicals. They could also be employed for carbon sequestration, the scientists say.
