The differential carbon-fixing and nitrogen-assimilating enzyme activities of Oscillatorian marine cyanobacterium Phormidium valderianum BDU 20041

Abstract

We have identified an efficient filamentous marine cyanobacterium, Phormidium valderianum BDU 20041, which was adaptive to different concentrations of CO2. In our study, P. valderianum BDU 20041 was grown under ambient (0.04) and elevated (2, 3, 4, 5, 10, and 15%) CO2 concentration. Its optimal growth occurred at 3% CO2 supply. P. valderianum displayed similar carbon fixation activities through Rubisco, phosphoenolpyruvate carboxylase (PEPC), carbonic anhydrase, and malate dehydrogenase. The activity of Rubisco, the primary carbon-fixing enzyme, was found to be approximately 80% higher in P. valderianum grown under 4% CO2 than under ambient air. This was substantiated by Western blot. The nitrogen-assimilating enzymes shared a similar trend at higher CO2 concentrations. Our study is one of the few reports that examined the activities of CO2-fixing and nitrogen-assimilating enzymes together. Due to the active PEPC, this cyanobacterium was found to have active C3 and C4 enzymes that promoted higher CO2 fixation and cellular growth. Thus, it may be an efficient organism for biotechnological exploitation.

Keywords

• biomass productivity; elevated co2 concentration; nitrate reductase; nitrite reductase.