Electrochemically Driven Photosynthetic Electron Transport in Cyanobacteria Lacking Photosystem II.

Light-activated photosystem II (PSII) carries out the critical step of splitting water in photosynthesis. However, PSII is susceptible to light-induced damage. Here, results are presented from a novel microbial electro-photosynthetic system (MEPS) that uses redox mediators in conjunction with an electrode to drive electron transport in live Synechocystis (Δ psbB ) cells lacking PSII. MEPS-generated, light-dependent current increased with light intensity up to 2050 μmol photons m -2 s -1 , which yielded a delivery rate of 113 μmol electrons h -1 mg-chl -1 and an average current density of 150 A m -2 s -1 mg-chl -1 . P700 + re-reduction kinetics demonstrated that initial rates exceeded wildtype PSII-driven electron delivery. The electron delivery occurs ahead of the cytochrome b 6 f complex to enable both NADPH and ATP production. This work demonstrates an electrochemical system that can drive photosynthetic electron transport, provides a platform for photosynthetic foundational studies, and has the potential for improving photosynthetic performance at high light intensities.