Studies of biouptake and transformation of mercury by a typical unicellular diatom Phaeodactylum tricornutum  

作　　者：DENG GuiFu ZHANG TianWen YANG LiMin WANG QiuQuan 

机构地区：[1]Department of Chemistry & the Key Laboratory of Analytical Science,College of Chemistry and Chemical Engineering,Xiamen University [2]State Key Laboratory of Marine Environmental Science,Xiamen University

出　　处：《Chinese Science Bulletin》2013年第2期256-265,共10页

基　　金：supported by the National Basic Research Program of China (2009CB421605);the National Natural Science Foundation of China (21035006)

摘　　要：Mercury(Hg) is a toxic heavy metal with its biogeochemical cycling in the ocean depending on the type and behavior of the oceanic microalgae.The present work aimed to evaluate bioaccumulation and transformation of Hg by Phaeodactylum tricornutum,a typical unicellular diatom,when exposed to the extremely high level of Hg in order to understand the possible mechanisms of acute stress response.P.tricornutum can accumulate Hg(its bioaccumulation factor is at 104 level),and the 96 h EC 50 was estimated to be 145μg L-1.The amounts of surface-bound Hg being about 1.2 to 4.8 times higher than those of intracellular Hg under exposure to HgCl 2(from 20 to 120μg L-1 concentrations) suggested that the cell wall of P.tricornutum is an important "fence" towards Hg.After entering the P.tricornutum cell,Hg underwent transformation in its chemical form via interactions with high molecular weight sulfur-containing proteins(accounting for 68% of the intracellular Hg),and glutathione as well as the induced phytochelatins(PCs)(24% Hg) which alleviated the toxicity of HgCl2.In addition,the existence of organic ligands greatly influenced the uptake and transformation behavior of P.tricornutum towards HgCl2,especially in the case of cysteine(Cys),which increased the uptake of Hg,but alleviated the toxicity of Hg towards P.tricornutum due to the fact that Cys is an important precursor for the synthesis of PCs inside the cell.The uptake process of Hg by P.tricornutum was in agreement with the Freundlich isotherm,suggesting a typical heterogeneous sorption process.More importantly,we observed the conversion of HgCl2 into methylmercury inside the P.tricornutum cells and its release into the culture solution using HPLC/CVG-AFS and GC-MS,although the mechanism needs to be further investigated.Mercury （Hg） is a toxic heavy metal with its biogeochemical cycling in the ocean depending on the type and behavior of the oceanic microalgae. The present work aimed to evaluate bioaccumulation and transformation of Hg by Phaeodactylum tricornutum, a typical unicellular diatom, when exposed to the extremely high level of Hg in order to understand the possible mechanisms of acute stress response. P. tricornutum can accumulate Hg （its bioaccumulation factor is at 104 level）, and the 96 h EC50 was estimated to be 145 μg L^-1 . The amounts of surface-bound Hg being about 1.2 to 4.8 times higher than those of intracellular Hg under exposure to HgCl2 （from 20 to 120 μg L^-1 concentrations） suggested that the cell wall of P. tricornutum is an important ＂fence＂ towards Hg. After entering the P. tricornutum cell, Hg underwent transformation in its chemical form via interactions with high molecular weight sulfur-containing proteins （accounting for 68% of the intracellular Hg）, and glutathione as well as the induced phytochelatins （PCs） （24% Hg） which alleviated the toxicity of HgCl2. In addition, the existence of organic ligands greatly influenced the uptake and transformation behavior of P. tricornutum towards HgCl2, especially in the case of cysteine （Cys）, which increased the uptake of Hg, but alleviated the toxicity of Hg towards P. tricornutum due to the fact that Cys is an important pre- cursor for the synthesis of PCs inside the cell. The uptake process of Hg by P. tricornutum was in agreement with the Freundlich isotherm, suggesting a typical heterogeneous sorption process. More importantly, we observed the conversion of HgCI2 into methylmercury inside the P. tricornutum cells and its release into the culture solution using HPLC/CVG-AFS and GC-MS, although the mechanism needs to be further investigated.

关 键 词：三角褐指藻 氯化汞 单细胞 改造 硅藻 生物地球化学循环 HgCl2 吸收过程 

分 类 号：X173[环境科学与工程—环境科学]