Department of Geography, The University of Sheffield, Sheffield, S10 2TN, UK.
Department of Materials Science and Engineering, Sir Robert Hadfield Building, University of Sheffield, Mappin Street, Sheffield, S1 3JD, UK.
Phys Chem Chem Phys. 2021 Jan 21;23(2):1566-1576. doi: 10.1039/d0cp04067c.
The bacterial cell envelope, in particular the cell wall, is considered the main controlling factor in the biosorption of aqueous uranium(vi) by microorganisms. However, the specific roles of the cell wall, associated biomolecules, and other components of the cell envelope are not well defined. Here we report findings on the biosorption of uranium by isolated cell envelope components and associated biomolecules, with P. putida 33015 and B. subtilis 168 investigated as representative strains for the differences in Gram-negative and Gram-positive cell envelope architecture, respectively. The cell wall and cell surface membrane were isolated from intact cells and characterised by X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FT-IR) spectroscopy; revealing variations in the abundance of functional moieties and biomolecules associated with components of the cell envelope. Uranium biosorption was investigated as a function of cell envelope component and pH, comparing with intact cells. The isolated cell wall from both strains exhibited the greatest uranium biosorption capacity. Deprotonation of favourable functional groups on the biomass as the pH increased from 3 to 5.5 increased their uranium biosorption capacity by approximately 3 fold. The results from ATR-FT-IR indicated that uranium(vi) biosorption was mediated by phosphate and carboxyl groups associated with proteins and phosphorylated biopolymers of the cell envelope. This includes outer membrane phospholipids and LPS of Gram-negative bacteria and teichoic acids, surface proteins and peptidoglycan from Gram-positive bacteria. As a result, the biosorption process of uranium(vi) to microorganisms is controlled by surface interactions, resulting in higher accumulation of uranium in the cell envelope. This demonstrates the importance of bacterial cell wall as the key mediator of uranium biosorption with microorganisms.
细菌的细胞包膜，特别是细胞壁，被认为是微生物对水溶液中铀(VI)的生物吸附的主要控制因素。然而，细胞壁、相关生物分子和细胞包膜的其他成分的具体作用尚未得到很好的定义。在这里，我们报告了用分离的细胞包膜成分和相关生物分子进行铀生物吸附的研究结果，用 P. putida 33015 和 B. subtilis 168 作为革兰氏阴性和革兰氏阳性细胞包膜结构差异的代表性菌株进行研究。细胞壁和细胞膜从完整细胞中分离出来，并通过 X 射线光电子能谱 (XPS) 和衰减全反射-傅里叶变换红外光谱 (ATR-FT-IR) 进行了表征；揭示了与细胞包膜成分相关的功能部分和生物分子的丰度变化。作为细胞包膜成分和 pH 的函数，研究了铀的生物吸附，与完整细胞进行了比较。两种菌株的分离细胞壁表现出最大的铀生物吸附能力。随着 pH 值从 3 增加到 5.5，生物量上有利的功能基团的去质子化增加了其铀生物吸附能力约 3 倍。ATR-FT-IR 的结果表明，铀(VI)的生物吸附是由与蛋白质和细胞包膜的磷酸化生物聚合物相关的磷酸根和羧基基团介导的。这包括革兰氏阴性菌的外膜磷脂和 LPS 以及革兰氏阳性菌的磷壁酸、表面蛋白和肽聚糖。因此，铀(VI)被微生物生物吸附的过程受到表面相互作用的控制，导致铀在细胞包膜中的积累更高。这证明了细菌细胞壁作为微生物铀生物吸附的关键介质的重要性。
