Scanning electron microscope image of Escherichia coli bacteria.

Escherichia coli bacteria normally derive carbon from food but can be altered to take it from the air. Credit: Martin Oeggerli/SPL

Synthetic biology

Thrifty bacteria thrive on something in the air

Borrowed genes help E. coli to subsist on the relatively modest levels of carbon dioxide in Earth’s atmosphere.

Plants, algae and other photosynthetic organisms draw their carbon from carbon dioxide in Earth’s atmosphere. This process is catalysed by an enzyme called Rubisco, which works inefficiently at atmospheric levels of CO2. As a workaround, many plants and other photosynthetic organisms use systems called CO2-concentrating mechanisms, which raise CO2 levels near this enzyme to improve its efficiency.

David Savage at the University of California, Berkeley, Ron Milo at the Weizmann Institute of Science in Rehovot, Israel, and their colleagues had previously engineered Escherichia coli bacteria to grow on CO2, instead of the bacterium’s preferred diet of sugars and other organic molecules. But their E. coli strain, which made use of Rubisco, grew only at artificially high levels of CO2.

To enable growth in atmospheric CO2 levels, the researchers added a set of 20 genes that code for the CO2-concentrating mechanism of the bacterium Halothiobacillus neapolitanus. The resulting E. coli strain can subsist on atmospheric CO2 levels.

Escherichia coli, which are easy to manipulate in the lab, could serve as a test bed for understanding other CO2-concentrating genes, the researchers say.