State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, People's Republic of China.
Australian Rivers Institute, Griffith University, 170 Kessels Road, Nathan, QLD 4111, Australia.
Proc Biol Sci. 2023 Jul 26;290(2003):20231204. doi: 10.1098/rspb.2023.1204. Epub 2023 Jul 19.
The inter-relationships between cellular phosphorus (P) storage, dissolved inorganic P (DIP) uptake affinity, alkaline phosphatase activity (APA) and dissolved inorganic nitrogen (DIN) concentrations were studied in two ubiquitous diazotrophic freshwater cyanobacteria, (six strains) and (two strains). DIP uptake kinetics were measured using rates of incorporation of the radio-isotope, P and APA as a proxy for DOP-ester utilization. The study showed that DIP uptake of individual strains followed Michaelis-Menten kinetics (modified in our study to incorporate cellular P quotas), but differed with DIN and P availability, and between growth stages. High-affinity DIP uptake and APA were activated below a P quota threshold of approximately 0.01 µg P µg C across the species and strains. had significantly higher APA and P quotas (per unit C and cell) but lower uptake affinity than . Demand for DIP by increased when N fixation occurred, but typically not for . Our results indicate that cyanobacterial species and strains differ in their strategies to P limiting conditions, and highlight the interplay between N and P. Physiological adaptations like APA and diazotrophy of cyanobacteria adapting to low DIP and/or DIN conditions may occur simultaneously and drive species dominance in oligotrophic environments.
在两种普遍存在的淡水固氮蓝藻中，研究了细胞磷（P）储存、溶解无机磷（DIP）摄取亲和力、碱性磷酸酶活性（APA）和溶解无机氮（DIN）浓度之间的相互关系， （六株）和 （两株）。使用放射性同位素 P 的掺入率和 APA 作为 DOP-酯利用的替代物来测量 DIP 摄取动力学。研究表明，个别菌株的 DIP 摄取遵循米氏动力学（在本研究中修改为纳入细胞 P 配额），但因 DIN 和 P 的可用性以及生长阶段而异。在种和菌株之间，高亲和力 DIP 摄取和 APA 在大约 0.01 µg P µg C 的细胞 P 配额阈值以下被激活。 具有明显更高的 APA 和 P 配额（每单位 C 和细胞），但比 摄取亲和力低。当固氮发生时， 对 DIP 的需求增加，但通常不是 。我们的研究结果表明，蓝藻物种和菌株在应对 P 限制条件的策略上存在差异，并强调了 N 和 P 的相互作用。适应低 DIP 和/或 DIN 条件的 APA 和蓝藻固氮等生理适应可能同时发生，并在贫营养环境中驱动物种优势。
