Self-Assembled Nanoscale Manganese Oxides Enhance Carbon Capture by Diatoms.

Continuous CO 2 emissions from human activities increase atmospheric CO 2 concentrations and affect global climate change. The carbon storage capacity of the ocean is 20-fold higher than that of the land, and diatoms contribute to approximately 40% of carbon capture in the ocean. Manganese (Mn) is a major driver of marine phytoplankton growth and the marine carbon pump. Here, we discovered self-assembled manganese oxides (MnO x ) for CO 2 fixation in a diatom-based biohybrid system. MnO x shared key features (e.g., di-μ-oxo-bridged Mn-Mn) with the Mn 4 CaO 5 cluster of the biological catalyst in photosystem II and promoted photosynthesis and carbon capture by diatoms/MnO x . The CO 2 capture capacity of diatoms/MnO x was 1.5-fold higher than that of diatoms alone. Diatoms/MnO x easily allocated carbon into proteins and lipids instead of carbohydrates. Metabolomics showed that the contents of several metabolites (e.g., lysine and inositol) were positively associated with increased CO 2 capture. Diatoms/MnO x upregulated six genes encoding photosynthesis core proteins and a key rate-limiting enzyme (Rubisco, ribulose 1,5-bisphosphate carboxylase-oxygenase) in the Calvin-Benson-Bassham carbon assimilation cycle, revealing the link between MnO x and photosynthesis. These findings provide a route for offsetting anthropogenic CO 2 emissions and inspiration for self-assembled biohybrid systems for carbon capture by marine phytoplankton.