Synthetic engineering of conductive biofilm development in the y-proteobacterium Shewanella oneidensis

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The aim of this proposal is to understand the boundary conditions of conductive biofilm development by Shewanella oneidensis on electrode surfaces and the synthetic development of an advanced ability of the organism to endogenously build these current producing structures. S. oneidensis is the best understood model organism regarding extracellular electron transfer and the ability to thrive with insoluble electron acceptors. Still, the achievable electron transfer rates with these electron acceptors are several fold lower compared to the other model organism for extracellular electron transfer – Geobacter sulfurreducens. Our research builds upon the hypothesis that the reduction of electron acceptors like hematite or the ability to produce a current in a bioelectrochemical system is correlated to the ability to produce conductive biofilms. This is corroborated by the ability of G. sulfurreducens cells to integrate conductive structures in its extracellular polymeric substance. In the proposed work we will fundamentally establish how biofilm production on anode surfaces by S. oneidensis can be steered by the addition of abiotic or biotic conductive structures. To this end we will use a recently establish microfluidic platform that was advanced for use with bioelectrochemical systems. We want to understand how the organism reacts to the integration of this material and what the maximum current densities are that can be established using these exogenous current collectors. This maximum current density will be the benchmark that we want to reach when we engineer S. oneidensis to endogenously produce conductive structures within its extracellular polymeric material. We will export outer membrane cytochromes into the matrix and will synthetically connect them via isopeptide bonds to other proteins on the surface of the cell. To reach this goal we will use the recently established SpyTag/SpyCatcher technology that allows the posttranslational connection of proteins.