(172b) Microbially Controlled Cu(I)-Catalyzed Alkyne-Azide Cycloaddition (CuAAC) Via Extracellular Electron Transfer

Extracellular electron transfer (EET) couples anaerobic bacterial respiration to the reduction of extracellular metal species. Directing EET to a suitable synthetic metal catalyst allows for biocatalytic control over Cu(I)-catalyzed Alkyne-Azide Cycloaddition (CuAAC). The well characterized protein pathway responsible for EET in S. oneidensis, the Mtr-pathway, makes it an interesting model bacterium for whole cell genetic and metabolic control over CuAAC. We found that both anaerobic and aerobic CuAAC was catalyzed by actively respirating S. oneidensis. Changes to the carbon source, affecting the central anaerobic metabolism, exerted metabolic control over conversion and kinetics. Furthermore, several reaction cycles with changes between these carbon sources switched the reaction between “OFF” and “ON” without requiring cellular regeneration. Due to the well-defined protein pathway, transcriptional regulation of several different EET-proteins, MtrC, MtrA, and CymA, allow for genetic control of the traditionally synthetic reaction. Additionally, preliminary screens indicated a high degree of modularity in both substrate scope and metal catalyst ligand. This robustness allowed the system to be applied for bioorthogonal labelling on live mammalian cells, to control engineered living materials, and for applications in a microfluidic screen for EET activity. In summary, these results demonstrate how EET can expand the whole cell microbial reaction scope by coupling redox driven catalysis to metabolic and genetic engineering.