Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Science, The University of Manchester, Manchester, United Kingdom.
Department of Earth and Environmental Sciences, The University of Ottawa, Ottawa, Canada.
Appl Environ Microbiol. 2023 Mar 29;89(3):e0217522. doi: 10.1128/aem.02175-22. Epub 2023 Feb 28.
The reduction of Sb(V)-bearing ferrihydrite by Geobacter sulfurreducens was studied to determine the fate of the metalloid in Fe-rich systems undergoing redox transformations. Sb(V) added at a range of concentrations adsorbed readily to ferrihydrite, and the loadings had a pronounced impact on the rate and extent of Fe(III) reduction and the products formed. Magnetite dominated at low (0.5 and 1 mol%) Sb(V) concentrations, with crystallite sizes decreasing at higher Sb loadings: 37-, 25-, and 17-nm particles for no-Sb, 0.5% Sb, and 1% Sb samples, respectively. In contrast, goethite was the dominant end product for samples with higher antimony loadings (2 and 5 mol%), with increased goethite grain size in the 5% Sb sample. Inductively coupled mass spectrometry (ICP-MS) analysis confirmed that Sb was not released to solution during the bioreduction process, and X-ray photoelectron spectroscopy (XPS) analyses showed that no Sb(III) was formed throughout the experiments, confirming that the Fe(III)-reducing bacterium Geobacter sulfurreducens cannot reduce Sb(V) enzymatically or via biogenic Fe(II). These findings suggest that Fe (bio)minerals have a potential role in limiting antimony pollution in the environment, even when undergoing redox transformations. Antimony is an emerging contaminant that shares chemical characteristics with arsenic. Metal-reducing bacteria (such as Geobacter sulfurreducens) can cause the mobilization of arsenic from Fe(III) minerals under anaerobic conditions, causing widespread contamination of aquifers worldwide. This research explores whether metal-reducing bacteria can drive the mobilization of antimony under similar conditions. In this study, we show that G. sulfurreducens cannot reduce Sb(V) directly or cause Sb release during the bioreduction of the Fe(III) mineral ferrihydrite [although the sorbed Sb(V) did alter the Fe(II) mineral end products formed]. Overall, this study highlights the tight associations between Fe and Sb in environmental systems, suggesting that the microbial reduction of Fe(III)/Sb mineral assemblages may not lead to Sb release (in stark contrast to the mobilization of As in iron-rich systems) and offers potential Fe-based remediation options for Sb-contaminated environments.
本研究旨在探讨在富含铁的体系中发生氧化还原转化时，金属硫杆菌对 Sb(V) 赋存的水铁矿的还原作用，以确定该类半金属的归宿。一系列浓度的 Sb(V) 易于被吸附到水铁矿上，负载量对铁（III）还原的速率和程度以及形成的产物有显著影响。在低 Sb(V) 浓度（0.5 和 1mol%）下，主要生成磁铁矿，随着 Sb 负载量的增加，其结晶尺寸减小：无 Sb、0.5% Sb 和 1% Sb 样品的晶粒尺寸分别为 37、25 和 17nm。相比之下，对于 Sb 负载量较高（2 和 5mol%）的样品，主要产物为针铁矿，并且在 5% Sb 样品中针铁矿晶粒尺寸增大。电感耦合等离子体质谱（ICP-MS）分析证实 Sb 并未在生物还原过程中释放到溶液中，X 射线光电子能谱（XPS）分析表明，整个实验过程中未形成 Sb(III)，这证实了铁（III）还原菌 Geobacter sulfurreducens 不能通过酶促或生物生成的 Fe(II)还原 Sb(V)。这些发现表明，即使在发生氧化还原转化时，铁（生物）矿物也可能在限制环境中的 Sb 污染方面发挥作用。Sb 是一种新兴的污染物，与砷具有化学相似性。在厌氧条件下，金属还原菌（如 Geobacter sulfurreducens）可导致砷从 Fe(III)矿物中释放出来，从而导致全球范围内的含水层受到广泛污染。本研究探讨了在类似条件下，金属还原菌是否会导致 Sb 的迁移。在这项研究中，我们表明 G. sulfurreducens 不能直接还原 Sb(V)，也不能在水铁矿的生物还原过程中导致 Sb 释放（尽管吸附的 Sb(V)改变了形成的 Fe(II)矿物最终产物）。总体而言，这项研究强调了环境系统中 Fe 和 Sb 之间的紧密联系，表明微生物还原 Fe(III)/Sb 矿物组合可能不会导致 Sb 释放（与富铁系统中 As 的释放形成鲜明对比），并为 Sb 污染环境提供了潜在的基于 Fe 的修复选择。
