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引用本文:陈成,郑超群,王梦梦,杨顺清,杨柳燕.低浓度硝态氮促进微囊藻累积多聚磷酸盐.湖泊科学,2022,34(3):766-776. DOI:10.18307/2022.0306
Chen Cheng,Zheng Chaoqun,Wang Mengmeng,Yang Shunqing,Yang Liuyan.Low concentration nitrate-nitrogen improves polyphosphate accumulation in Microcystis. J. Lake Sci.2022,34(3):766-776. DOI:10.18307/2022.0306
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低浓度硝态氮促进微囊藻累积多聚磷酸盐
陈成, 郑超群, 王梦梦, 杨顺清, 杨柳燕
南京大学环境学院, 污染控制与资源化研究国家重点实验室, 南京 210023
摘要:
2016年以来太湖总磷浓度高位波动而总氮浓度持续下降,藻细胞内源性磷释放是湖泊水体总磷的重要来源,而多聚磷酸盐作为藻细胞内磷的储存库,其含量变化会显著影响藻细胞内源性磷的释放量.针对上述现象,开展了不同硝态氮浓度影响野外水华蓝藻及实验室纯培养的铜绿微囊藻(Microcystis aeruginosa)利用磷特别是合成多聚磷酸盐(PolyP)的研究,并通过测定低硝态氮浓度下铜绿微囊藻的光合活性以及抗氧化系统活性,探索低硝态氮浓度促进微囊藻合成PolyP的生理机制.研究结果表明,当水体硝态氮浓度低于2 mg/L时,水华蓝藻和铜绿微囊藻均能大量吸收磷酸盐,并在胞内累积PolyP.同时,由于水体中可利用氮浓度下降,铜绿微囊藻胞内蛋白质干重(0.6 mg/mg)也显著下降.此时,铜绿微囊藻细胞的光合活性仍能达到高氮对照组的75.1%~88.7%,但由于碳和氮同化潜力的下降,较强的光合活性导致细胞内活性氧累积,使细胞处于氧化应激状态,导致藻细胞内蛋白质、核酸和细胞膜结构受损.而由于PolyP具有保护作用,微囊藻合成大量PolyP,以适应缺氮的水环境,导致蓝藻奢侈吸磷.因此,低硝态氮促进微囊藻累积多聚磷酸盐,从而提升细胞内总磷含量,而高含磷蓝藻衰亡释放磷,就会增加水体中总磷浓度.
关键词:  水华蓝藻|铜绿微囊藻|多聚磷酸盐|硝态氮|氧化应激
DOI:10.18307/2022.0306
分类号:
基金项目:国家自然科学基金项目(41871082)和江苏省生态环境厅科研课题项目(2020019)联合资助.
Low concentration nitrate-nitrogen improves polyphosphate accumulation in Microcystis
Chen Cheng, Zheng Chaoqun, Wang Mengmeng, Yang Shunqing, Yang Liuyan
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, P. R. China
Abstract:
Lake Taihu, a shallow lake located in the eastern plain of China, has been plagued by eutrophication and cyanobacterial outbreaks due to the highest population density and industrial and agricultural development in the region. Total phosphorus concentrations have fluctuated at high levels while total nitrogen concentrations have continued to decrease in Lake Taihu since 2016. The release of endogenous phosphorus from algal cells is an important source of total phosphorus in the lake, and the level of polyphosphate (PolyP), a reservoir of phosphorus in algal cells, significantly affects the release of endogenous phosphorus from algal cells. In response to this phenomenon, we conducted a study on the potential of phosphorus utilization, especially polyphosphate synthesis by blooming cyanobacteria and Microcystis aeruginosa under different nitrate nitrogen concentrations. By measuring the photosynthetic activity and antioxidant system activity of M. aeruginosa under low nitrate nitrogen concentration, we explored the physiological mechanism that how low nitrate nitrogen concentration promotes the excessively synthesis of PolyP in Microcystis. The results showed that both blooming cyanobacteria and M. aeruginosa had luxury uptake of PO43- and intracellular accumulation of PolyP if the nitrate nitrogen concentration was below 2 mg/L, while the intracellular protein dry weight (0.6 mg/mg) of M. aeruginosa also decreased significantly due to the decrease of available nitrogen elements in water. Meanwhile, the photosynthetic activity of M. aeruginosa could still reach 75.1%-88.7% of the control group, but due to the decrease of carbon and nitrogen assimilation capacity, the relatively strong photosynthetic activity led to the accumulation of intracellular reactive oxygen species, which put the cells in an oxidative stress status to induce the activation of antioxidant system. The dual dilemma of low nitrogen content and oxidative stress prompted cyanobacterial cells to synthesize PolyP in large quantities to prevent the damages of protein, nucleic acid and cell membrane structure in cyanobacterial cells. Thus, the adverse conditions of nitrogen deficiency led to increase cyanobacterial intracellular phosphorus content. If the cyanobacterial cells decayed, a large amount of PO43- was released into the water column to cause the increase of total phosphorus in water body under the low nitrate nitrogen condition.
Key words:  Blooming cyanobacteria|Microcystis aeruginosa|polyphosphate|nitrate-nitrogen|oxidative stress
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