State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Ecotoxicol Environ Saf. 2023 Sep 15;263:115378. doi: 10.1016/j.ecoenv.2023.115378. Epub 2023 Aug 18.
A detailed understanding the metals binding with algal organic matter (AOM) is essential to gain a deeper insight into the toxicity and migration of metals in algae cell. However, the molecular complexation mechanism of the metals binding with AOM remains unclear. In this study, cadmium ion (Cd) binding properties of AOMs from Scenedesmus obliquus, which included extracellular organic matter (EOM) and intracellular organic matter (IOM), were screened. When Cd < 0.5 mg/L, the accumulation of Cd could reach 40%, while Cd > 0.5 mg/L, the accumulation of Cd was only about 10%. EOM decreased gradually (from 8.51 to 3.98 mg/L), while IOM increased gradually (from 9.62 to 21.00 mg/L). The spectral characteristics revealed that IOM was richer in peptides/proteins and had more hydrophilic than EOM. Both EOM and IOM contained three protein-like components (containing tryptophan and tyrosine) and one humic-like component, and their contents in IOM were higher than that in EOM. The tryptophan protein-like substances changed greatly during Cd binding, and that the tryptophan protein-like substances complexed to Cd before tyrosine protein-like substances in IOM was identified. Moreover, the functional groups of N-H, O-H, and CO in AOM played an important role, and the N-H group was priority to interacts with Cd in the complexing process. More functional groups (such as C-O and C-N) were involved in the metals complexing in EOM than in IOM. It could be concluded that Cd stress promoted the secretion of AOM in Scenedesmus obliquus, and proteins in AOM could complex Cd and alleviate its toxicity to algal cell. These findings provided deep insights into the interaction mechanism of AOM with Cd in aquatic environments.
深入了解金属与藻类有机物质（AOM）的结合对于深入了解金属在藻类细胞中的毒性和迁移至关重要。然而，金属与 AOM 结合的分子络合机制尚不清楚。本研究筛选了斜生栅藻的 AOM（包括胞外有机物质（EOM）和胞内有机物质（IOM））对镉离子（Cd）的结合特性。当 Cd <0.5 mg/L 时，Cd 的积累量可达 40%，而 Cd >0.5 mg/L 时，Cd 的积累量仅约为 10%。EOM 逐渐减少（从 8.51 降至 3.98 mg/L），而 IOM 逐渐增加（从 9.62 增至 21.00 mg/L）。光谱特征表明，IOM 比 EOM 含有更多的肽/蛋白质，且具有更高的亲水性。EOM 和 IOM 均含有三个类蛋白成分（含有色氨酸和酪氨酸）和一个类腐殖质成分，且 IOM 中的含量高于 EOM。Cd 结合过程中色氨酸类蛋白物质变化较大，鉴定出 IOM 中的色氨酸类蛋白物质先于酪氨酸类蛋白物质与 Cd 络合。此外，AOM 中的 N-H、O-H 和 CO 等功能基团在络合过程中发挥了重要作用，且 N-H 基团优先与 Cd 相互作用。EOM 中涉及的功能基团（如 C-O 和 C-N）比 IOM 更多，参与了金属的络合。可以得出结论，Cd 胁迫促进了斜生栅藻分泌 AOM，AOM 中的蛋白质可以络合 Cd，减轻其对藻类细胞的毒性。这些发现为深入了解水生环境中 AOM 与 Cd 的相互作用机制提供了依据。
