In a remarkable breakthrough that could pave the way toward carbon-neutral fuels, researchers at the Weizmann Institute of Science have produced a genetically engineered bacteria that can live on carbon dioxide rather than sugar.
The extraordinary leap — reported Wednesday in Cell, and quickly picked up by prestigious publications such as Nature — could lead to the low-emissions production of carbon for use in biofuels or food that would also help to remove excess CO₂ from the atmosphere, where it is helping to drive global warming.
Plants and ocean-living cyanobacteria perform photosynthesis, taking the energy from light to transform CO₂ into a form of organic carbon that can be used to build DNA, proteins and fats.
As these photosynthesizers can be difficult to moderate genetically, the Weizmann team, under Prof. Ron Milo, took E. coli bacteria — more commonly associated with food poisoning — and spent ten years weaning them off sugar and training them to “eat” carbon dioxide instead.
Through genetic engineering, they enabled the bacteria to convert CO₂ into organic carbon, substituting the energy of the sun — a vital ingredient in the photosynthesis process — with a substance called formate, which is also attracting attention as a potential generator of clean electricity.
To get the bacteria to move from a sugar to a carbon dioxide diet, the team, which also included Roee Ben-Nissan, Yinon Bar-On and others in the institute’s Plant and Environmental Sciences Department, then almost starved the bacteria of sugar (glucose), while giving them plenty of carbon dioxide and formate, and bred several generations to test whether evolution would allow some of the bacteria to mutate and be able to survive solely on CO₂.
After a year, some of the bacteria descendants made the complete switch to CO₂, following evolutionary changes in just 11 genes.
The lab bacteria that moved over to a CO₂ diet were fed very high amounts of the gas. However, under regular atmospheric conditions, they would still need sugar, as well, to live.
“Our lab was the first to pursue the idea of changing the diet of a normal heterotroph [one that eats organic substances] to convert it to autotrophism [‘living on air’],” said Milo. “It sounded impossible at first, but it has taught us numerous lessons along the way, and in the end we showed it indeed can be done. Our findings are a significant milestone toward our goal of efficient, green scientific applications.”