(513h) Tuning Extracellular Electron Transfer to Control Polymer Synthesis

Electroactive bacteria can extend the scope of metabolism-controlled transformations to include inorganic processes, such as transition-metal catalysis and nanoparticle formation. Shewanella oneidensis has become a popular chassis organism for such applications, owing to its genetic tractability and well-studied mechanisms of extracellular electron transport. Specifically, its Mtr cytochrome pathway has been the focus of much optimization for increasing current flow to (in)soluble metals and electrodes – primarily through overexpression of key network components. However, quenching of electron transfer by the microbe has proven more challenging; the dynamic range of engineered electron transport activity has been limited to the timescale of microbial fuel cell operation (days/weeks), posing a challenge for the rapid changes needed in actuating material synthesis (minutes/hours). Here, we present progress in tuning the temporal dynamics of electron transfer activity via genetic circuitry-based expressional control and targeted mutagenesis of the terminal reductase, MtrC. Control of electron flow by the bacteria was enabled using chemical and physical inducers. We demonstrate the utility of these engineering efforts in a Shewanella-enabled material synthesis developed by our group: controlled radical polymerization. Generated polymers exhibited properties that were dependent on the rate of electron transfer. We envision this toolkit could be used to further manipulate bioelectrically powered chemical and material syntheses.