Impact of different nitrogen regimes on the central metabolism of marine microalgae of the genus Nannochloropsis

Marine microalgae play a pivotal role in global primary production, being responsible for approximately 50% of the oxygen we breathe. Nitrogen (N) is essential for life, being a central component of nucleic acids, amino acids, and pigments and thus is also essential for the central metabolism of marine microalgae. The relationship between carbon (C) and N metabolism in marine microalgae is vital for their growth and metabolic homeostasis. N assimilation generates pigments and proteins used by photosynthesis, while C metabolism generates C skeletons essential for the N assimilation mechanism. This study examines the interaction between N and C assimilation in two marine microalgae species belonging to the genus Nannochloropsis, namely N. gaditana and N. oceanica. The species were studied under various C, N, and light conditions, including atmospheric CO2 and 1% CO2, low and high light intensities, and different nitrate (NO3-) concentrations. Microalgae growth, NO3- consumption, and key photosynthetic parameters were monitored. The results showed faster NO3- consumption with higher CO2 and irradiance, highlighting the interaction between C and N metabolisms indeed. This research underscores the importance of understanding the dynamic relationship between C and N metabolisms in marine microalgae to investigate their population dynamics in nature as a function of changing environmental parameters and, at the same time, to improve cultivation practices for industrial applications of these organisms for biotechnology.