PDF(Pubmed)
Abstract：
The main entrance point of highly toxic organic Hg forms, including methylmercury (MeHg), into the aquatic food web is phytoplankton, which is greatly represented by various natural microalgal species. Processes associated with MeHg fate in microalgae cells such as uptake, effects on cells and toxicity, Hg biotransformation, and intracellular stability are detrimental to the process of further biomagnification and, as a consequence, have great importance for human health. The study of MeHg uptake and distribution in cultures of marine halophile Dunaliella salina and freshwater acidophilic alga Coccomyxa onubensis demonstrated that most of the MeHg is imported inside the cell, while cell surface adhesion is insignificant. Almost all MeHg is removed from the culture medium after 72 h. Significant processes in rapid MeHg removal from liquid medium are its abiotic photodegradation and volatilization associated with algal enzymatic activity. The maximum intracellular accumulation for both species was in 80 nM MeHg-exposed cultures after 24 h of exposure for D. salina (from 27 to 34 µg/gDW) and at 48 h for C. onubensis (up to 138 µg/gDW). The different Hg intakes in these two strains could be explained by the lack of a rigid cell wall in D. salina and the higher chemical ability of MeHg to pass through complex cell wall structures in C. onubensis. Electron microscopy studies on the ultrastructure of both strains demonstrated obvious microvacuolization in the form of many very small vacuoles and partial cell membrane disruption in 80 nM MeHg-exposed cultures. Results further showed that Coccomyxa onubensis is a good candidate for MeHg-contaminated water reclamation due to its great robustness at nanomolar concentrations of MeHg coupled with its very high intake and almost complete Hg removal from liquid medium at the MeHg levels tested.
摘要：
高毒性有机汞形式的主要入口点，包括甲基汞（MeHg），进入水生食物网的是浮游植物，其中以各种天然微藻物种为代表。与微藻细胞中甲基汞命运相关的过程，如摄取，对细胞和毒性的影响，汞生物转化，和细胞内稳定性不利于进一步的生物放大过程，因此，对人类健康非常重要。对海洋嗜盐菌盐藻和淡水嗜酸性藻培养物中甲基汞的吸收和分布的研究表明，大多数甲基汞是在细胞内输入的，而细胞表面粘附是微不足道的。72小时后，几乎所有MeHg都从培养基中去除。从液体培养基中快速去除MeHg的重要过程是其非生物光降解和挥发与藻类酶活性有关。两种物种的最大细胞内积累都是在暴露于盐藻24小时后的80nMMeHg培养物中（从27到34µg/gDW）和在48小时时的C.onubensis（高达138µg/gDW）。这两个菌株中汞的摄入量不同可以解释为盐藻中缺乏刚性细胞壁，以及MeHg通过C.onubensis中复杂细胞壁结构的较高化学能力。对这两个菌株的超微结构的电子显微镜研究表明，在80nMMeHg暴露的培养物中，明显的微空泡以许多非常小的液泡和部分细胞膜破坏的形式出现。结果进一步表明，Coccomyxaonubensis是受甲基汞污染的水回收的良好候选者，因为它在纳摩尔浓度的甲基汞下具有很强的鲁棒性，并且在测试的甲基汞水平下，其摄入量非常高，并且几乎完全从液体培养基中去除汞。
