Nature and Value of Freely Dissolved EPS Ecosystem Services: Insight into Molecular Coupling Mechanisms for Regulating Metal Toxicity
Nature and Value of Freely Dissolved EPS Ecosystem Services: Insight into Molecular Coupling Mechanisms for Regulating Metal Toxicity
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自由溶解的 EPS 生态系统服务的性质和价值：洞察调节金属毒性的分子耦合机制
DOI：
10.1021/acs.est.7b04834
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发表时间：
2018
影响因子：
11.4
通讯作者：
Lu Jiahao
中科院分区：
文献类型：
--
作者：
Shou Weijun;Kang Fuxing;Lu Jiahao
分散在天然水中的胞外聚合物 (EPS) 在减轻重金属释放对微生物生存的影响方面发挥着重要作用，但人们对自由溶解的 EPS 生态系统服务与天然水中金属转化的关系知之甚少。在这里，我们证明分散 EPS 通过缔合配位反应减轻金属对微生物细胞的毒性。微量滴定法与荧光光谱相结合，将大肠杆菌 (E. coli) 中自由溶解的 EPS 与 Cu2+/Cd2+ 的结合归因于与化学静态猝灭相关的配位反应。傅里叶变换红外光谱 (FTIR)、X 射线光电子能谱 (XPS) 和计算化学证实 EPS 类蛋白质物质中的羧基残基负责配位。去质子化羧基的前沿分子轨道 (MO) 与 Cu2+ 和/或 Cd2+ 的山梨醇占据的轨道整合，形成金属-EPS 复合物。微观系统表明，由于金属-EPS 复合物降低了金属的细胞吸收能力，E. Cu2+ 和 Cd2+ 的大肠杆菌存活率分别增加 4.3 倍和 1.6 倍。基于六种金属-EPS 配位的键能，缔合毒性效应进一步证实，键能的增加有利于 EPS 基质中金属的延迟，从而防止大肠杆菌。结肠凋亡。
Extracellular polymeric substances (EPSs) dispersed in natural waters play a significant role in relieving impacts to microbial survival associated with heavy metal release, yet little is known about the association of freely dissolved EPS ecosystem services with metal transformation in natural waters. Here, we demonstrate that dispersive EPSs mitigate the metal toxicity to microbial cells through an associative coordination reaction. Microtitrimetry coupled with fluorescence spectroscopy ascribes the combination of freely dissolved EPSs fromEscherichia coli(E. coli) with Cu2+/Cd2+to a coordination reaction associated with chemical static quenching. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and computational chemistry confirm that carboxyl residues in protein-like substances of the EPSs are responsible for the coordination. Frontier molecular orbitals (MOs) of a deprotonated carboxyl integrate with the occupieddorbitals of Cu2+and/ord,sorbitals of Cd2+to form metal-EPS complexes. Microcosmic systems show that because the metal-EPS complexes decrease cellular absorbability of metals,E. colisurvivals increase by 4.3 times for Cu2+and 1.6 times for Cd2+, respectively. Based on bonding energies for six metals-EPS coordination, an associative toxic effect further confirms that increased bonding energies facilitate retardation of metals in the EPS matrix, protecting againstE. coliapoptosis.