Cadmium and proton adsorption onto a halophilic archaeal species: The role of cell envelope sulfhydryl sites
Cadmium and proton adsorption onto a halophilic archaeal species: The role of cell envelope sulfhydryl sites
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DOI：
10.1016/j.gca.2020.02.038
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发表时间：
2020-05
影响因子：
5
通讯作者：
Jinling Liu;Qiang Yu;Allison R. Showalter;B. Bunker;J. Swanson;D. Reed;Xingmin Rong;J. Fein
中科院分区：
文献类型：
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作者：
Jinling Liu;Qiang Yu;Allison R. Showalter;B. Bunker;J. Swanson;D. Reed;Xingmin Rong;J. Fein
古细菌对金属的吸附可能会影响金属在高盐度环境中的行为和生物有效性，因为在高盐度环境中，古细菌是主要的生命形式。然而，嗜盐古菌吸附金属的机理和热力学还不是很清楚。本研究通过Cd吸附实验和电位滴定模拟嗜盐古细菌对金属离子的吸附。Cd在古菌细胞上的吸附表现出缓慢的吸附动力学，需要8 h才能达到稳态。Cd的吸附程度强烈地依赖于PCH+和Cd的负载量。Cd的解吸甚至比吸附更慢，但吸附Cd的生物体暴露在高浓度的半胱氨酸下促进了Cd的解吸，表明Cd的分布是由可逆吸附反应控制的，可能涉及Cd在细胞表面的巯基结合。我们进行了有无巯基封闭的电位滴定实验，得到古菌细胞被膜中的总巯基浓度为91 ± 28 μ/g。结合Showalter等人的X射线吸收精细结构分析结果。(2016)和本研究的Cd吸附测量和滴定数据，我们构建了Cd吸附行为的表面络合模型。由于Cd的吸附行为可能与一系列亲胆碱的微量营养素的吸附行为相似，因此Cd-巯基结合的重要性表明，古细菌产生高亲和力的巯基结合位点可能代表着嗜盐微生物在金属-氯络合水溶液主导许多金属形态的环境中获得金属营养的一种适应性策略。
The adsorption of metal onto archaea could affect metal behavior and bioavailability in hypersaline environments where archaea represent the dominant life form. However, the mechanism and thermodynamics of metal adsorption onto halophilic archaea are not well understood. In this study, Cd adsorption experiments and potentiometric titrations were conducted to model metal adsorption by the halophilic archaeonHalobacteriumsp.. Cd adsorption onto the archaeal cells exhibits slow adsorption kinetics, taking 8 h to reach steady-state. The extent of Cd adsorption depends strongly on pCH+and Cd loading. Desorption of Cd is even slower than adsorption, but exposure of the Cd-adsorbed biomass to high concentrations of cysteine promotes desorption and demonstrates that the distribution of Cd is controlled by reversible adsorption reactions, likely involving sulfhydryl binding of Cd on the cell surface. We conducted potentiometric titration experiments with and without sulfhydryl site blocking to yield a total sulfhydryl site concentration of 91 ± 28 μmol/g within the archaeal cell envelope. Using a combination of the X-ray absorption fine structure analysis results from Showalter et al. (2016) and the Cd adsorption measurements and titration data from this study, we construct a surface complexation model of the Cd adsorption behavior. Because the Cd adsorption behavior is likely similar to that of a range of chalcophilic micronutrients, the importance of Cd-sulfhydryl binding suggests that the production of high affinity sulfhydryl binding sites by the archaea may represent an adaptive strategy for halophiles to obtain metal nutrients in environments in which aqueous metal-chloride complexation dominates the speciation for many metals.