Bacteria Switch To Consuming Carbon Dioxide For Growth

Over the course of several months, researchers in Israel created Escherichia coli strains that consume CO2 for energy instead of organic compounds. This achievement in synthetic biology highlights the incredible plasticity of bacterial metabolism and could provide the framework for future carbon-neutral bioproduction.

Our main aim was to create a convenient scientific platform that could enhance CO2 fixation, which can help address challenges related to the sustainable production of food and fuels and global warming caused by CO2 emissions," says senior author Ron Milo, at systems biologist at the Weizmann Institute of Science. "Converting the carbon source of E. coli, the workhorse of biotechnology, from organic carbon into CO2 is a major step towards establishing such a platform."

The living world is divided into autotrophs that convert inorganic CO2 into biomass and heterotrophs that consume organic compounds. Autotrophic organisms dominate the biomass on Earth and supply much of our food and fuels. A better understanding of the principles of autotrophic growth and methods to enhance it is critical for the path to sustainability.

A grand challenge in synthetic biology has been to generate synthetic autotrophy within a model heterotrophic organism. Despite widespread interest in renewable energy storage and more sustainable food production, past efforts to engineer industrially relevant heterotrophic model organisms to use CO2 as the sole carbon source has failed. Previous attempts to establish autocatalytic CO2 fixation cycles in model heterotrophs always required the addition of multi-carbon organic compounds to achieve stable growth.

In the Cell study, the researchers used metabolic rewiring and lab evolution to convert E. coli into autotrophs. The engineered strain harvests energy from a formate, which can be produced electrochemically from renewable sources. Because formate is an organic one-carbon compound that does not serve as a carbon source for E. coli growth, it does not support heterotrophic pathways. The researchers also engineered the strain to produce non-native enzymes for carbon fixation and reduction and for harvesting energy from formate.