Toxic Effects of Mercury on the Photosynthetic System of Unicellualr Cyanobacterium Synechocystis sp.PCC 6803
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-1significantly inhibited thylakoid function,reduced pigment content,disrupted photosynthetic electron transport,and led to the inactivation of some photosystem Ⅱ(PS Ⅱ)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 PS Ⅱ centers.This study identifies QA,QB,and the PS Ⅱ 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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