Progress on photosynthetic nitrogen assimilation and its regulatory mechanisms in cyanobacteria

Abstract

水华蓝藻的生物学特性及其竞争优势、蓝藻水华的形成与维持机制等科学问题，一直是国内外研究的热点。氮素是诱发蓝藻水华暴发的重要营养盐，蓝藻对氮素的同化与其光合作用密切偶联。然而，水体中氮素存在多种形态，不同形态氮素对蓝藻生长和水华发生的影响具有显著差异。因此，了解蓝藻光合作用特征及其同化不同形态氮素的机制和策略，对深入理解蓝藻水华的发生机理具有重要意义。本文在蓝藻的光能捕获与激发能转移、光合电子传递、碳浓缩机制及CO₂同化等光合作用过程及其特征综述的基础上，对蓝藻摄取、同化5种主要氮素形态（NO₃^-、NO₂^-、NH₄⁺、尿素和N₂）的分子机制及其特征进行了解读，总结了蓝藻细胞光合碳、氮同化的耦合关系及调控机制；并指出了该领域的未来发展方向，以推动该方向的深入研究。;The biological characteristics and competitive predominance of cyanobacteria, as well as the formation and maintenance mechanism of cyanobacteria blooms, have aroused continuous interests among researchers. As an important nutrient for cyanobacterial growth, the assimilation of nitrogen is intimately coupled with the photosynthesis. However, nitrogen exists in various chemical forms in water, which affect the cyanobacterial growth and the formation of blooms in distinct ways. To delve into the formation mechanism of cyanobacterial blooms, it is important to understand the cyanobacterial photosynthetic feature as well as the mechanism and strategy by which the nitrogen of different forms are assimilated into cyanobacteria. This paper reviewed the processes and characteristics of photosynthesis in cyanobacteria, such as light energy capture and excitation energy transfer, primary photosynthetic reaction, CO₂ concentrating mechanism and assimilation. Then, it illustrated the transport and assimilation of different nitrogen forms (NO₃^-, NO₂^-, NH₄⁺, urea and N₂), the regulation of these processes, as well as the mechanisms by which cells coordinate and regulate the carbon/nitrogen metabolism. The paper also summarized the latest research advances in cyanobacterial blooms and suggested on the content and direction of further research.