Biology Department, and CBC (Centro de Biologia Celular), University of Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal.
Ecotoxicology. 2013 Jan;22(1):166-73. doi: 10.1007/s10646-012-1013-1. Epub 2012 Nov 4.
The ubiquity of diatom distribution, species richness, short generation time, and specific sensitivity to several environmental stressors such as metals, make diatoms particularly useful for scientific studies. Anthropogenic activities have increased the concentration of metals in air, soil and water. Due to their toxicity and persistent character, the effects of metals on organisms have been extensively studied. In this work, the association of cadmium to different extracellular molecules of Nitzschia palea cells was investigated. Cells were grown in the absence and presence (0.2 mg l(-1)) of cadmium in Chu no. 10 medium. Extracellular polysaccharides were extracted, and subsamples were used for polysaccharide and Cd determination. The frustules were broken mechanically under liquid nitrogen and the intracellular and frustule fractions separated. Frustulins, a protein family found on the outmost frustule layer, constituting a protection coating to environmental stress, were extracted. In each fraction proteins were quantified by the BCA method and separated by gel electrophoresis (SDS-PAGE). Cadmium associated to each fraction was quantified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis. Exposure of Nitzschia palea to cadmium decreased extracellular polysaccharides by 52.8 % and increased 6 times the amount of frustulins. Cadmium was mostly retained extracellularly: 85.4 % was bound to the frustulin fraction, and 11.1 % to polysaccharides. The ability of Nitzschia palea to increase the production of frustulins due to the presence of Cd, the extracellular location of this frustulin coating and the ability of these proteins to bind Cd, suggests a new cellular defense mechanism to metals unknown until now.
硅藻的分布广泛、物种丰富、世代时间短，并且对多种环境胁迫因素（如金属）具有特异性敏感性，这使得硅藻特别适合用于科学研究。人为活动增加了空气中、土壤中和水中金属的浓度。由于金属的毒性和持久性，金属对生物的影响已被广泛研究。在这项工作中，研究了镉与 palea 角毛藻细胞不同胞外分子的结合。细胞在 Chu no. 10 培养基中培养，分别在有无镉（0.2mg l(-1))的情况下进行。提取了胞外多糖，并对多糖和 Cd 进行了测定。将藻壳在液氮下机械破碎，分离出胞内和藻壳部分。从最外层的藻壳层上发现的一种蛋白质家族——frustulins 被提取出来，frustulins 构成了一种对环境胁迫的保护涂层。在每个部分中，通过 BCA 方法定量蛋白质，并通过凝胶电泳（SDS-PAGE）进行分离。通过电感耦合等离子体质谱（ICP-MS）分析定量与各部分结合的镉。palea 角毛藻暴露于镉会使胞外多糖减少 52.8%，并使 frustulins 的含量增加 6 倍。镉主要存在于胞外：85.4%与 frustulin 部分结合，11.1%与多糖结合。由于 Cd 的存在，palea 角毛藻增加了 frustulins 的产量，这种 frustulin 涂层位于胞外，以及这些蛋白质结合 Cd 的能力，表明了一种以前未知的金属细胞防御新机制。
