Engineering electroautotrophy

My lab is developing a bacterial strain that will catalyze the conversion of carbon dioxide to fuels and products using electrons from an electrode as the sole source of reducing power. This process would represent a new form of metabolism – electroautotrophy. Our platform for developing an electroautotrophic strain is Shewanella oneidensis, a metal-reducing bacterium that already possesses the capacity to exchange electrons with extracellular electrodes. The first key challenge in this project is to create an efficient pathway for electron flow from the electrode to intracellular electron carriers. This requires reversing the direction of electron flow through the native extracellular electron transfer pathway in S. oneidensis. We have demonstrated proof-of-concept for the inward electron transfer pathway by engineering S. oneidensis to catalyze the intracellular reduction of acetoin to 2,3-butanediol using an electrode as the electron source. We are currently working to improve flux through the inward electron transfer pathway by over-expressing the essential components. The second key challenge is to transplant a carbon fixation pathway into S. oneidensis, which is a heterotroph. We have expressed the missing components of the Calvin-Benson-Bassham cycle for carbon fixation in S. oneidensis and are currently working to functionalize the pathway through adaptive laboratory evolution. Moving forward, we will combine the modifications required for inward electron transfer and for carbon fixation to create the electroautotrophic strain.