Li Jingxin, Zhang Yuxiao, Zheng Shiling, Liu Fanghua, Wang Gejiao
State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China.
Key Laboratory of Coastal Biology and Biological Resources Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, China.
Front Microbiol. 2019 Feb 27;10:360. doi: 10.3389/fmicb.2019.00360. eCollection 2019.
Antimony (Sb) pollution is a worldwide problem. In some anoxic sites, such as Sb mine drainage and groundwater sediment, the Sb concentration is extremely elevated. Therefore, effective Sb remediation strategies are urgently needed. In contrast to microbial aerobic antimonite [Sb(III)] oxidation, the mechanism of microbial anaerobic Sb(III) oxidation and the effects of nitrate and Fe(II) on the fate of Sb remain unknown. In this study, we discovered the mechanism of anaerobic Sb(III) oxidation coupled with Fe(II) oxidation and denitrification in the facultative anaerobic Sb(III) oxidizer sp. GW3. We observed the following: (1) under anoxic conditions with nitrate as the electron acceptor, strain GW3 was able to oxidize both Fe(II) and Sb(III) during cultivation; (2) in the presence of Fe(II), nitrate and Sb(III), the anaerobic Sb(III) oxidation rate was remarkably enhanced, and Fe(III)-containing minerals were produced during Fe(II) and Sb(III) oxidation; (3) qRT-PCR, gene knock-out and complementation analyses indicated that the arsenite oxidase gene product AioA plays an important role in anaerobic Sb(III) oxidation, in contrast to aerobic Sb(III) oxidation; and (4) energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (XRD) analyses revealed that the microbially produced Fe(III) minerals were an effective chemical oxidant responsible for abiotic anaerobic Sb(III) oxidation, and the generated Sb(V) was adsorbed or coprecipitated on the Fe(III) minerals. This process included biotic and abiotic factors, which efficiently immobilize and remove soluble Sb(III) under anoxic conditions. The findings revealed a significantly novel development for understanding the biogeochemical Sb cycle. Microbial Sb(III) and Fe(II) oxidation coupled with denitrification has great potential for bioremediation in anoxic Sb-contaminated environments.
锑（Sb）污染是一个全球性问题。在一些缺氧场所，如锑矿排水和地下水沉积物中，锑浓度极高。因此，迫切需要有效的锑修复策略。与微生物好氧亚锑酸盐[Sb(III)]氧化不同，微生物厌氧Sb(III)氧化的机制以及硝酸盐和Fe(II)对锑归宿的影响仍然未知。在本研究中，我们发现了兼性厌氧Sb(III)氧化菌GW3中厌氧Sb(III)氧化与Fe(II)氧化和反硝化作用耦合的机制。我们观察到以下几点：（1）在以硝酸盐为电子受体的缺氧条件下，菌株GW3在培养过程中能够氧化Fe(II)和Sb(III)；（2）在存在Fe(II)、硝酸盐和Sb(III)的情况下，厌氧Sb(III)氧化速率显著提高，并且在Fe(II)和Sb(III)氧化过程中产生了含Fe(III)的矿物；（3）定量逆转录聚合酶链反应（qRT-PCR）、基因敲除和互补分析表明，与好氧Sb(III)氧化不同，亚砷酸盐氧化酶基因产物AioA在厌氧Sb(III)氧化中起重要作用；（4）能量色散X射线光谱（EDS）、X射线光电子能谱（XPS）和粉末X射线衍射（XRD）分析表明，微生物产生的Fe(III)矿物是负责非生物厌氧Sb(III)氧化的有效化学氧化剂，生成的Sb(V)被吸附或共沉淀在Fe(III)矿物上。这个过程包括生物和非生物因素，能够在缺氧条件下有效地固定和去除可溶性Sb(III)。这些发现揭示了理解生物地球化学锑循环的一个重大新进展。微生物Sb(III)和Fe(II)氧化与反硝化作用耦合在缺氧锑污染环境的生物修复中具有巨大潜力。
