Bacteria modified to consume CO2

29 November 2019

E COLI

Esterichia coli

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If you find it difficult to change your diet, look at what these bacteria did…

Scientists successfully made E.coli bacteria change their diets dramatically, to consume carbon dioxide rather than food.

“It’s a real transformation from what is known a heterotroph into an autotroph,” explains Israel's Weizmann Institute researcher Ron Milo, who led the new study.

Autotrophs, like plants, take CO2 from the environment and use energy, for example from sunlight, to produce biomass, organic matter that can be used as fuel. Heterotrophs, like us humans on the other hand, are organisms that consume organic matter and release CO2.

Rather than using sunlight as a source of energy like plants do, the modified E.coli bacteria extracted energy from a material called formate.

According to Milo, they use formate because “bacteria can’t assimilate it into their bodies, and can only use it as an energy source by transfer of electrons. At the same time, it is a compound that can be produced electrochemically.”

The researchers succeeded in modifying the nutritional preferences of their E.coli by first genetically modifying the digestion process of the bacteria, and then forcing them to evolve in a specific way across a number of bacterial generations.

“In the first step, the rational design, we are adding components into the cell that are genes that code for the process of carbon fixation, as well as deleting some genes that otherwise waste energy for the cell,” explains Milo.

“The second step is laboratory evolution, in which you take the bacteria and put them under conditions of strong selection such that they are given ample CO2 and energy but very little sugar, such that there is a very strong motivation for the adaptation process to depend only on CO2.”

The next steps in Milo’s research will be to “understand the genetic basis of the laboratory evolution process, and then to adapt the cells further into being able to work at ambient atmospheric conditions.”

For the moment, these bacteria revert back to consuming sugar for their food when it is readily available and the CO2 levels drop below the amount fed during the lab evolution process. If they achieve this, then these bacteria could potentially be used to actively remove CO2 from the atmosphere.

“Currently, what we have is something that emits more CO2 than is being absorbed. This is in the current implementation using formate, but in the future one could use alternative energy sources, such as direct renewable energy, that could create a net negative carbon dioxide process.”

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