Uncovering the Differential Growth of Microcystis aeruginosa Cultivated under Nitrate and Ammonium from a Photophysiological Perspective

Abstract

Cyanobacteria have a relatively high affinity for NH4 +, yet a NO3 –-rich environment is comparatively conducive to their proliferation. To date, little information is available on why NO3 –-N favors cyanobacterial biomass accumulation. This study investigated the dependence of biomass, nitrogen assimilation characteristics, and photophysiological performance of Microcystis aeruginosa on the forms of nitrogen supply, including NO3 –-N-only, NH4 +-N-only, and NO3 –-N + NH4 +-N. The results indicated that despite the retarded growth of M. aeruginosa, cells supplied with NO3 –-N-only maintained a simultaneous promotion in the growth rate, nitrogen assimilation efficiency, and photosynthetic capacity, resulting in high biomass production. Cells supplied with NH4 +-N-only and NO3 –-N + NH4 +-N were able to rapidly assimilate nitrogen during initial cell proliferation, showing a preferential use of NH4 +-N and the inhibition of NO3 – uptake by NH4 +. However, growth repression occurred as cultivation time was prolonged when NH4 +-N was excessively supplied, mainly due to PSII photodamage, intracellular redox imbalance, and increased electron energy accumulation. Thus, cells supplied with NH4 +-N-only had to reduce light energy capture, increase photoprotection, and consume excess electrons to mitigate the damage. These findings are critical for improving our understanding of the role of different nitrogen forms in the regulation of cyanobacterial photophysiological performance and growth.

Simulating short-term light responses of photosynthesis and water use efficiency in sweet sorghum under varying temperature and CO2 conditions

“…A n , WUE i , WUE inst ) with increased light intensity, but also in accurately determining critical photosynthetic traits across diverse temperatures and CO 2 conditions. These findings align with previous research applying the Ye's models to Cyanobacteria ( Yang et al., 2022 ; Yang et al, 2023 ), Chlorophyta, Bacillariophyta ( Yang et al., 2020 ), and other plants ( Xu et al., 2012 ; Atsushi et al., 2017 ; Martínez-García et al., 2017 ; Liu et al., 2018 ; Ye et al., 2020 ), demonstrating its broad utility.…”

Addressing the long-standing limitations of double exponential and non-rectangular hyperbolic models in quantifying light-response of electron transport rates in different photosynthetic organisms under various conditions

“…The algal cells were subjected to starvation treatment and then inoculated into the BG11 medium, containing 10 ml g -1 of NO 3 – N (NaNO 3 ) or 10 ml/g of NH 4 + -N (NH 4 Cl). When the algal density reached 1.8 × 10 6 cells mL -1 , the J - I curves of the algal were measured with the built-in program of a Phyto-PAM fluorescence monitoring system manufactured by Walz Germany ( Yang et al., 2023 ).…”

“…We further conducted a comparison between the fits of the J – I curves obtained from our mechanistic model and those obtained from a highly classic DE model. We note that the DE model has been earlier used to simulate the J–I curves in algae and cyanobacteria ( Platt et al., 1980 ; Harrison and Platt, 1986 ; Henley, 1993 ; Rascher et al., 2000 ; Ralph and Gademann, 2005 ; Karageorgou and Manetas, 2006 ; Yang et al., 2023 ), but rarely in plants due to differences in the physiology and light response characteristics of these photosynthetic species. The DE model is expressed as follows:…”

“…Generally, for algae and cyanobacteria, the J–I curve is divided into three distinct parts depending on the light intensity levels: (1) light-limited, (2) light-saturated, and (3) photoinhibitory/dynamic down-regulation of PSII ( Ralph and Gademann, 2005 ). The J level increases almost linearly with the increasing light intensity over the light-limited region until the light intensity reaches the saturation level ( I sat ), after which the J level decreases with the increasing light intensity due to dynamic down-regulation of PSII/photoinhibition induced by high light intensity ( Ralph and Gademann, 2005 ; Suggett et al., 2007 ; Yang et al., 2023 ). However, the division of the J–I curve for plants is much more complex ( Robakowski, 2005 ; Ye et al., 2013a , b , 2016 , 2019 ; Hu et al., 2021 ; He et al., 2022 ; Robakowski et al., 2022 ).…”

“…The NRH model has been extensively applied to fit the J–I curves of plants, but it has only provided values of α and J max ( Long and Bernacchi, 2003 ; von Caemmerer, 2013 ; Ye et al., 2019 ; Yin et al., 2021 ). However, the mechanistic model (developed by Ye et al., 2013a , b ) has been found to be increasingly of use in simulating the J–I curves of algae, cyanobacteria, and plants, as well as in obtaining the values of α , J max and I sat ( Serodio et al., 2013 ; Ye et al., 2013a ; Morfopoulos et al., 2014 ; Sun et al., 2015 ; Ahammed et al., 2018 ; Robakowski et al., 2018 ; Yang et al., 2018 ; Ye et al., 2019 ; Robakowski et al., 2022 ; Yang et al., 2023 ). These models provide valuable tools for understanding the photosynthetic performance of different photosynthetic organisms under various environmental conditions.…”