Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom
Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom.
Appl Environ Microbiol. 2020 Sep 1;86(18). doi: 10.1128/AEM.00967-20.
Biomineralization of Cu has been shown to control contaminant dynamics and transport in soils. However, very little is known about the role that subsurface microorganisms may play in the biogeochemical cycling of Cu. In this study, we investigate the bioreduction of Cu(II) by the subsurface metal-reducing bacterium Rapid removal of Cu from solution was observed in cell suspensions of when Cu(II) was supplied, while transmission electron microscopy (TEM) analyses showed the formation of electron-dense nanoparticles associated with the cell surface. Energy-dispersive X-ray spectroscopy (EDX) point analysis and EDX spectrum image maps revealed that the nanoparticles are rich in both Cu and S. This finding was confirmed by X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses, which identified the nanoparticles as CuS. Biomineralization of CuS nanoparticles in soils has been reported to enhance the colloidal transport of a number of contaminants, including Pb, Cd, and Hg. However, formation of these CuS nanoparticles has only been observed under sulfate-reducing conditions and could not be repeated using isolates of implicated organisms. As is unable to respire sulfate, and no reducible sulfur was supplied to the cells, these data suggest a novel mechanism for the biomineralization of CuS under anoxic conditions. The implications of these findings for the biogeochemical cycling of Cu and other metals as well as the green production of Cu catalysts are discussed. Dissimilatory metal-reducing bacteria are ubiquitous in soils and aquifers and are known to utilize a wide range of metals as terminal electron acceptors. These transformations play an important role in the biogeochemical cycling of metals in pristine and contaminated environments and can be harnessed for bioremediation and metal bioprocessing purposes. However, relatively little is known about their interactions with Cu. As a trace element that becomes toxic in excess, Cu can adversely affect soil biota and fertility. In addition, biomineralization of Cu nanoparticles has been reported to enhance the mobilization of other toxic metals. Here, we demonstrate that when supplied with acetate under anoxic conditions, the model metal-reducing bacterium can transform soluble Cu(II) to CuS nanoparticles. This study provides new insights into Cu biomineralization by microorganisms and suggests that contaminant mobilization enhanced by Cu biomineralization could be facilitated by species and related organisms.
生物矿化作用已被证明可以控制土壤中污染物的动态和迁移。然而，对于地下微生物在铜的生物地球化学循环中可能扮演的角色，我们知之甚少。在这项研究中，我们研究了地下金属还原菌 Rapid 对 Cu(II)的生物还原作用。当提供 Cu(II)时，观察到细胞悬浮液中 Cu 的快速去除，而透射电子显微镜 (TEM) 分析表明，与细胞表面相关的电子致密纳米颗粒的形成。能量色散 X 射线光谱 (EDX) 点分析和 EDX 光谱图像地图表明，纳米颗粒富含 Cu 和 S。这一发现通过 X 射线吸收近边结构 (XANES) 和扩展 X 射线吸收精细结构 (EXAFS) 分析得到证实，这些分析将纳米颗粒鉴定为 CuS。已经报道了在土壤中生物矿化 CuS 纳米颗粒可以增强包括 Pb、Cd 和 Hg 在内的许多污染物的胶体迁移。然而，只有在硫酸盐还原条件下才观察到这些 CuS 纳米颗粒的形成，并且不能使用涉及的生物分离物重复形成。由于 Rapid 无法呼吸硫酸盐，并且没有向细胞提供可还原的硫，这些数据表明了在缺氧条件下生物矿化 CuS 的新机制。这些发现对 Cu 和其他金属的生物地球化学循环以及 Cu 催化剂的绿色生产的影响进行了讨论。异化金属还原菌在土壤和含水层中无处不在，已知它们将多种金属用作末端电子受体。这些转化在原始和污染环境中金属的生物地球化学循环中起着重要作用，并且可以用于生物修复和金属生物加工目的。然而，关于它们与 Cu 的相互作用，我们知之甚少。作为一种在过量时会变得有毒的微量元素，Cu 会对土壤生物群和肥力产生不利影响。此外，已经报道了 Cu 纳米颗粒的生物矿化可以增强其他有毒金属的迁移。在这里，我们证明了在缺氧条件下，当提供乙酸盐时，模式金属还原菌 Rapid 可以将可溶性 Cu(II)转化为 CuS 纳米颗粒。这项研究为微生物的 Cu 生物矿化提供了新的见解，并表明 Cu 生物矿化增强的污染物迁移可能由 Rapid 种及其相关生物来促进。
