Nitrogen Availability Affects the Metabolic Profile in Cyanobacteria

Nitrogen is essential for the biosynthesis of various molecules in cells, such as amino acids and nucleotides, as well as several types of lipids and sugars. Cyanobacteria can assimilate several forms of nitrogen, including nitrate, ammonium, and urea, and the physiological and genetic responses to these nitrogen sources have been studied previously. However, the metabolic changes in cyanobacteria caused by different nitrogen sources have not yet been characterized. This study aimed to elucidate the influence of nitrate and ammonium on the metabolic profiles of the cyanobacterium Synechocystis sp. strain PCC 6803. When supplemented with NaNO(3) or NH(4)Cl as the nitrogen source, Synechocystis sp. PCC 6803 grew faster in NH(4)Cl medium than in NaNO(3) medium. Metabolome analysis indicated that some metabolites in the CBB cycle, glycolysis, and TCA cycle, and amino acids were more abundant when grown in NH(4)Cl medium than NaNO(3) medium. (15)N turnover rate analysis revealed that the nitrogen assimilation rate in NH(4)Cl medium was higher than in NaNO(3) medium. These results indicate that the mechanism of nitrogen assimilation in the GS-GOGAT cycle differs between NaNO(3) and NH(4)Cl. We conclude that the amounts and biosynthetic rate of cyanobacterial metabolites varies depending on the type of nitrogen.