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 (Δ) cells lacking PSII. MEPS-generated, light-dependent current increased with light intensity up to 2050 μmol photons m s, which yielded a delivery rate of 113 μmol electrons h mg-chl and an average current density of 150 A m s mg-chl. P700 re-reduction kinetics demonstrated that initial rates exceeded wildtype PSII-driven electron delivery. The electron delivery occurs ahead of the cytochrome 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.