Effects of the Δ13c Abundance Of Carbon Source On Carbon Fixation Of Nitzschia Closterium: Stable Isotope Analysis and Metabolomic Studies

The accumulation of excess CO2 in the atmosphere has been associated with a closely related decrease in the 13C/12C ratio of the CO2. However, our knowledge on the impacts of the carbon isotopic compositions of carbon source on photosynthetic carbon fixation of algal and its underlying mechanisms remains limited. Here, the effects of the isotopicaliy light carbon source on carbon fixation of Nitzschia closterium were evaluated using metabolomics, stable isotope techniques, enzyme analysis and physiological indicators. The results showed that the isotopicaliy light carbon source promoted algal growth and carbon fixation. Stable isotope analysis indicated that algal absorbed atmosphere CO2for photosynthesis, and the isotopicaliy light carbon source resulting in a lower δ13C of algal. Enzyme analysis showed that the ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity increased under low abundance of carbon source. Metabolomics further rrevealed that the isotopicaliy light carbon source upregulated TCA cycle of the algal, and carbon source mainly flowed to amino acids and fatty acid synthesis pathway. Overall, the changes in the port areasprovides new insights on the photosynthetic carbon fixation mechanisms of the algal and the marine carbon cycling under increasing atmospheric CO2.