Lu Yang, Hu Shiwen, Zhang Hanyue, Song Qingmei, Zhou Wenjing, Shen Xinyue, Xia Di, Yang Yang, Zhu Huiyan, Liu Chongxuan
South China Institute of Environmental Sciences, Ministry of Ecology and Environment (MEE), 7 West Street, Yuancun, Guangzhou, Guangdong 510655, People's Republic of China.
State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of the Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China.
Sci Total Environ. 2022 Nov 25;849:157713. doi: 10.1016/j.scitotenv.2022.157713. Epub 2022 Jul 29.
Interfacial reactions between iron (Fe) (hydr)oxide surfaces and the activity of bacteria during dissimilatory Fe reduction affect extracellular electron transfer. The presence of organic matter (OM) and exposed facets of Fe (hydr)oxides influence this process. However, the underlying interfacial mechanism of facet-dependent hematite and its toxicity toward microbes during bioreduction in the presence of OM remains unknown. Herein, humic acid (HA), as typical OM, was selected to investigate its effect on the bioreduction of hematite {100} and {001}. When HA concentration was increased from 0 to 500 mg L, the bioreduction rates increased from 0.02 h to 0.04 h for hematite {100} and from 0.026 h to 0.05 h for hematite {001}. Since hematite {001} owned lower resistance than hematite {100} irrespective of the HA concentration, and hematite {100} was less favorable for reduction. Microscopy-based analysis showed that more hematite {001} nanoparticles adhered to the cell surface and were bound more closely to the bacteria. Moreover, less cell damage was observed in the HA-hematite {001} treatments. As the reaction progressed, some bacterial cells died or were inactivated; confocal laser scanning microscopy showed that bacterial survival was higher in the HA-hematite {001} treatments than in the HA-hematite {100} treatments after bioreduction. Spectroscopic analysis revealed that facet-dependent binding was primarily realized by surface complexation of carboxyl functional groups with structural Fe atoms, and that the binding order of HA functional groups and hematite was affected by the exposed facets. The exposed facets of hematite could influence the electrochemical properties and activity of bacteria, as well as the binding of bacteria and Fe oxides in the presence of OM, thereby governing the extracellular electron transfer and concomitant bioreduction of Fe (hydr)oxides. These results provide new insights into the interfacial reactions between OM and facet-dependent Fe oxides in anoxic, OM-rich soil and sediment environments.
铁（氢）氧化物表面与异化铁还原过程中细菌活性之间的界面反应会影响细胞外电子转移。有机物（OM）的存在以及铁（氢）氧化物暴露的晶面会影响这一过程。然而，在存在OM的情况下，晶面依赖性赤铁矿的潜在界面机制及其在生物还原过程中对微生物的毒性仍然未知。在此，选择腐殖酸（HA）作为典型的OM，以研究其对赤铁矿{100}和{001}生物还原的影响。当HA浓度从0增加到500 mg/L时，赤铁矿{100}的生物还原速率从0.02 h增加到0.04 h，赤铁矿{001}的生物还原速率从0.026 h增加到0.05 h。由于无论HA浓度如何，赤铁矿{001}的电阻都低于赤铁矿{100}，且赤铁矿{100}不利于还原。基于显微镜的分析表明，更多的赤铁矿{001}纳米颗粒附着在细胞表面并与细菌结合得更紧密。此外，在HA-赤铁矿{001}处理中观察到的细胞损伤较少。随着反应的进行，一些细菌细胞死亡或失活；共聚焦激光扫描显微镜显示，生物还原后，HA-赤铁矿{001}处理中的细菌存活率高于HA-赤铁矿{100}处理。光谱分析表明，晶面依赖性结合主要通过羧基官能团与结构铁原子的表面络合实现，并且HA官能团与赤铁矿的结合顺序受暴露晶面的影响。赤铁矿的暴露晶面可以影响细菌的电化学性质和活性，以及在存在OM的情况下细菌与铁氧化物的结合，从而控制细胞外电子转移和伴随的铁（氢）氧化物生物还原。这些结果为缺氧、富含OM的土壤和沉积物环境中OM与晶面依赖性铁氧化物之间的界面反应提供了新的见解。
