Enhancing Cyanobacterial Photosynthetic Carbon Fixation via Quenching Reactive Oxygen Species by Intracellular Gold Nanoparticles

Reactive oxygen species (ROS) play an important rolein sensingthe redox pressure involved in the electron transfer chains of photosynthesis.However, due to variation in light, ROS accumulation originated fromthe excess electrons on the acceptor side of photosystem I gives riseto critical inhibition of photosynthetic carbon fixation. How to regulatethe extent to which ROS decrease stimulates energy and metabolic fluxesbeyond nature must be known to improve CO2 fixation. Herein,we report a strategy to deliver biocompatible gold nanoparticles intocyanobacterium Synechocystis sp. PCC6803 to dispatch the photosynthetic electron hub for improving CO2 fixation. Biomass of the cyanobacteria increases to 1.6 timeswith intracellular Au nanoparticles. The enzyme-like gold nanoparticlesquench 30% ROS from flavodiiron proteins Flv and increase 21% apparentoxygen evolution, boosting the enzymatic activity of glyceraldehyde3-phosphate dehydrogenase by an increase of 40% under high light stress.In comparison, gold nanoparticles have no obvious effect on the photosyntheticcarbon fixation of the Flv-deficient strain because of severe photoinhibitionof photosystems. This intracellular biohybrid strategy for interventionand modulation of complex photosynthetic electron transfer providesnew insight into energy conversion and CO2 fixation ofphotosynthesis. Intracellulargold nanoparticles regulate cyanobacterialphotosynthetic electron flows to 3-phosphoglycerate reduction of thecarbon fixation process for enhanced biomass accumulation.