汞对单细胞蓝藻——集胞藻的光合系统的毒性效应
Toxic Effects of Mercury on the Photosynthetic System of Unicellualr Cyanobacterium Synechocystis sp. PCC 6803
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摘要: 汞对藻类细胞的作用位点和毒性效应尚未完全阐明。为了深入探讨这一问题，本研究以集胞藻(Synechocystis sp. PCC 6803)为受试对象，在Hg2+浓度为0.000、0.005、0.010、0.020、0.030、0.040和0.050 mg·L-1的条件下处理96 h，并测定了藻细胞的OD730nm、光合色素含量、叶绿素荧光活性等生理指标。结果表明，当Hg2+浓度超过0.03 mg·L-1时，集胞藻的类囊体功能受到显著抑制，光合色素含量减少，光合电子传递受到阻碍，部分光系统II(PSⅡ)反应中心失活，最终导致集胞藻的最大光化学效率(Fv/Fm)下降，光合作用活性降低。同时，藻细胞通过增强剩余活性反应中心的功能，减缓了汞对光合系统的损伤。研究表明，PSⅡ中的QA、QB以及反应中心是Hg2+胁迫下集胞藻细胞的主要作用靶点。阐明这一问题可为深入理解水环境中汞污染的特性，并掌握藻类细胞对汞离子胁迫的响应机制提供重要依据。Abstract: The specific sites of action and toxic effects of mercury on algal cells remain incompletely understood. To address this gap, this study selected Synechocystis sp. PCC 6803 as the model organism and exposed it to Hg2+ at concentrations of 0.000, 0.005, 0.010, 0.020, 0.030, 0.040, and 0.050 mg·L-1 over 96 h. Physiological indicators such as OD730nm, photosynthetic pigment content, and chlorophyll fluorescence activity were measured. The results revealed that Hg2+ concentrations above 0.03 mg·L-1 significantly inhibited thylakoid function, reduced pigment content, disrupted photosynthetic electron transport, and led to the inactivation of some photosystem Ⅱ (PSⅡ) reaction centers. These effects caused a decline in maximum photochemical efficiency (Fv/Fm) and overall photosynthetic activity. In addition, the algal cells partially mitigated the damage by enhancing the activity of the remaining functional PSⅡ centers. This study identifies QA, QB, and the PSⅡ reaction center as the primary targets of Hg2+ stress in Synechocystis cells. These findings provide critical insights into the mechanisms of mercury pollution in aquatic environments and the cellular response to mercury ion stress.
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Key words:
- mercury /
- Synechocystis sp. /
- photosystem Ⅱ /
- toxic effect
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