The Molecular Choreography of Efficient Microbial Carbon Capture

As the scientific community seeks sustainable solutions to reduce our carbon dioxide (CO₂) footprint, nature offers an abundance of inspiration. In addition to photosynthesis, six other natural pathways are known by which living organisms remove CO­­₂ from the atmosphere to turn it into biomass. Understanding how these pathways work at an atomic level is an important step on the road to engineering climate solutions. The oldest CO­₂-fixation pathway, used in many oxygen-free environments, is known as the Wood-Ljungdahl pathway (WLP). The WLP is the most energy-efficient CO₂-fixation pathway, allowing anaerobic bacteria and archaea to generate ATP through CO₂ fixation. 

A multidisciplinary work, led by Bonnie Murphy, Tristan Wagner and Gerhard Hummer, and involving researchers from the Max Planck Institutes of Biophysics, Marine Microbiology and Molecular Cell Biology and Genetics, solved the mysteries of the central enzyme of the WLP: the Carbon Monoxide Dehydrogenase/Acetyl-CoA Synthase (CODH/ACS) complex. This enzyme performs a dual function, first transforming CO₂ to carbon monoxide (CO), and then using the CO to produce a central building block of metabolism called Acetyl-CoA. 

Using a combination of electron microscopy, X-ray crystallography and computational techniques, the Max Planck researchers studied the architecture of CODH/ACS from the bacterium Clostridium autoethanogenum, a microbe that is used in industrial bioreactors to turn industrial waste gasses into biofuels. “It was very challenging to reconstitute the native complex under an atmosphere without oxygen because we had to purify the three different proteins at the same time to provide the highest quality sample for cryo-EM studies,” says lead author Olivier Lemaire from the MPI for Marine Microbiology.