Abstract 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 archaeon Halobacterium sp.. 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.

中文翻译：

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镉和质子吸附到嗜盐古菌物种上：细胞包膜巯基位点的作用

摘要 金属在古细菌上的吸附会影响金属在高盐环境中的行为和生物利用度，其中古细菌代表了主要的生命形式。然而，金属吸附到嗜盐古菌上的机制和热力学尚不清楚。在这项研究中，进行了 Cd 吸附实验和电位滴定来模拟嗜盐古菌 Halobacterium sp. 对金属的吸附。古菌细胞上的 Cd 吸附表现出缓慢的吸附动力学，需要 8 小时才能达到稳态。Cd 吸附的程度很大程度上取决于 pCH+ 和 Cd 负载。Cd 的解吸甚至比吸附更慢，但吸附 Cd 的生物质暴露于高浓度的半胱氨酸会促进解吸，并表明 Cd 的分布受可逆吸附反应控制，可能涉及细胞表面 Cd 的巯基结合。我们进行了有和没有巯基位点封闭的电位滴定实验，以在古菌细胞包膜内产生 91 ± 28 μmol/g 的总巯基位点浓度。使用 Showalter 等人的 X 射线吸收精细结构分析结果的组合。(2016) 以及来自本研究的 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。因为 Cd 的吸附行为可能类似于一系列嗜硫微量营养素的行为，