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

Reactive oxygen species (ROS) play an important role in sensing the redox pressure involved in the electron transfer chains of photosynthesis. However, due to variation in light, ROS accumulation originated from the excess electrons on the acceptor side of photosystem I gives rise to critical inhibition of photosynthetic carbon fixation. How to regulate the extent to which ROS decrease stimulates energy and metabolic fluxes beyond nature must be known to improve CO2 fixation. Herein, we report a strategy to deliver biocompatible gold nanoparticles into cyanobacterium Synechocystis sp. PCC 6803 to dispatch the photosynthetic electron hub for improving CO2 fixation. Biomass of the cyanobacteria increases to 1.6 times with intracellular Au nanoparticles. The enzyme-like gold nanoparticles quench 30% ROS from flavodiiron proteins Flv and increase 21% apparent oxygen evolution, boosting the enzymatic activity of glyceraldehyde 3-phosphate dehydrogenase by an increase of 40% under high light stress. In comparison, gold nanoparticles have no obvious effect on the photosynthetic carbon fixation of the Flv-deficient strain because of severe photoinhibition of photosystems. This intracellular biohybrid strategy for intervention and modulation of complex photosynthetic electron transfer provides new insight into energy conversion and CO2 fixation of photosynthesis.