J Hazard Mater：NMT为Si提升藻耐Cd力提供证据

海洋浮游植物拥有复杂的体内平衡网络以抵消金属毒性。环境条件的变化（例如环境营养物浓度）会显着影响其固有的金属敏感性。
在这项研究中，我们评估了硅（Si）在抵消海洋硅藻Phaeodactylum tricornutum中镉（Cd）毒性中的作用。我们首先证明了Si富集显着提高了Cd耐受性并改变了硅藻中Cd的积累。
我们的模型表明，富硅细胞比缺硅细胞吸收更多的镉，但镉去除率更高。通过原子力显微镜和X射线光电子能谱检查发现，富硅细胞具有更好的硅化作用，并且细胞壁中的SiO-含量更高，这显着降低了硅藻细胞的表面电势并使它们吸收更多的Cd。
尽管富含Si的细胞在面对Cd胁迫时倾向于具有高的Cd负担，但是它们通过下调流入转运蛋白ZIP和上调流出转运蛋白ATPase5-1B来抑制细胞内Cd的增加。
我们的研究表明，硅在携带金属稳态和对抗海洋硅藻中的Cd挑战中起着重要作用。

Fig. 3. Cd2+ fluxes around the cell surface of the diatom P. tricornutum in the testing medium containing 8.9 μM Cd2+. (A) Instant net Cd2+ fluxes measured by a non-invasive microelectrode probe; (B) mean Cd2+ fluxes for the L-, M-, and H-Si cells. Means do not significantly differ (p>0.05) if they bear the same letter (n = 6). L, low; M, mid; H, high.

英文摘要

Marine phytoplankton possess a sophisticated homeostatic network to counteract metal toxicity. Changes in environmental conditions such as ambient nutrient concentrations can significantly impact their intrinsic metal sensitivity.
In this study, we evaluated the role of silicon (Si) in counteracting cadmium (Cd) toxicity in the marine diatom Phaeodactylum tricornutum. We first demonstrated that Si enrichment dramatically enhanced Cd tolerance and changed the Cd accumulation in the diatom.
Our modeling suggested that Si-enriched cells adsorbed more Cd but had a higher Cd elimination rate than the Si-starved cells. Examinations by atomic force microscopy and X-ray photoelectron spectroscopy revealed that the Si-enriched cells had better silification andmore SiO- in the cell walls, which markedly lowered the surface potential of the diatom cells and allowed them to attract more Cd.
Although the Si-enriched cells tended to have a high Cd burden when facing Cd stress, they suppressed the increase of intracellular Cd by both down-regulating the influx transporter ZIP and up-regulating the efflux transporter ATPase5-1B.
Our study shows the significant roles Si plays in maintaining metal homeostasisand combating Cd challenge in marine diatoms.