Optogenetics for Control of Biofilm Deposition and Extracellular Electron Transfer in Shewanella Oneidensis MR-1

Shewanella oneidensis MR-1 is a model electroactive bacterium, whose extracellular electron transfer (EET) pathway includes a network of multiheme c-type cytochromes to route electrons from the cellular interior to external, solid electron acceptors. S. oneidensis MR-1 is able to form living conductive biofilms on electrode surfaces for long-distance electron transport. Optogenetics circuits combine the light-sensitive proteins and transcription factors for spatiotemporal control of gene expression within living organisms as a response to illumination with light. Here, we introduced optogenetic circuits into S. oneidensis to control the electron transfer with different scales. We first developed a lithographic strategy to pattern conductive biofilms of S. oneidensis by controlling expression of the aggregation protein CdrAB with the blue light-induced genetic circuit pDawn. This controlled deposition enabled S. oneidensis biofilm patterning on transparent electrode surfaces and electrochemical measurements allowed us to demonstrate tunable conduction of living biofilms dependent on pattern geometry. Next, we developed a red light-induced genetic circuit in S. oneidensis based on a reported iLight system. This red light-induced genetic circuit was used to control the cytochromes expression in S. oneidensis which allowed us to adjust the extracellular electron transfer activity of S. oneidensis with light. Overall, these two new genetic tools enabled the control of biofilm conduction and EET activity by light which could have implications for both studying and harnessing bioelectronics.