Nitrogen Availability Affects the Metabolic Profile in Cyanobacteria

Abstract

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 NaNO3 or NH4Cl as the nitrogen source, Synechocystis sp. PCC 6803 grew faster in NH4Cl medium than in NaNO3 medium. Metabolome analysis indicated that some metabolites in the CBB cycle, glycolysis, and TCA cycle, and amino acids were more abundant when grown in NH4Cl medium than NaNO3 medium. 15N turnover rate analysis revealed that the nitrogen assimilation rate in NH4Cl medium was higher than in NaNO3 medium. These results indicate that the mechanism of nitrogen assimilation in the GS-GOGAT cycle differs between NaNO3 and NH4Cl. We conclude that the amounts and biosynthetic rate of cyanobacterial metabolites varies depending on the type of nitrogen.

Arginine inhibits the arginine biosynthesis rate-limiting enzyme and leads to the accumulation of intracellular aspartate in Synechocystis sp. PCC 6803

“…Synechocystis 6803 uses various nitrogen sources such as nitrate (NO 3 − ), nitrite (NO 2 − ), ammonium (NH 4 + ), urea [CO(NH 2 ) 2 ], and amino acids (arginine, glutamate, and glutamine), preferentially utilizing ammonium (Quintero et al 2001 ; Valladares et al 2002 ; Flores et al 2005 ; Muro-Pastor et al 2005 ). Synechocystis 6803 grows more rapidly in the presence of ammonium than nitrate (Inabe et al 2021 ). After uptake, these inorganic nitrogen sources, except for amino acids, are converted to ammonium and utilized for nitrogen assimilation via the glutamine synthetase-glutamate synthase (GS-GOGAT) cycle (Esteves-Ferreira et al 2018 ; Mills et al 2020 ).…”

“…After uptake, these inorganic nitrogen sources, except for amino acids, are converted to ammonium and utilized for nitrogen assimilation via the glutamine synthetase-glutamate synthase (GS-GOGAT) cycle (Esteves-Ferreira et al 2018 ; Mills et al 2020 ). Glutamate is primarily consumed as a nitrogen source and is distributed in various cellular building blocks (Forchhammer and Selim 2020 ; Inabe et al 2021 ).…”