Jiang Na, Feng Yiqing, Huang Qiang, Liu Xiaoling, Guo Yuan, Yang Zhen, Peng Chao, Li Shun, Hao Likai
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China.
Institute of Geochemistry, University of Chinese Academy of Sciences, Beijing, China.
Front Microbiol. 2022 May 12;13:885098. doi: 10.3389/fmicb.2022.885098. eCollection 2022.
Freshwater lakes are often polluted with various heavy metals in the Anthropocene. The iron-oxidizing microorganisms and their mineralized products can coprecipitate with many heavy metals, including Al, Zn, Cu, Cd, and Cr. As such, microbial iron oxidation can exert a profound impact on environmental remediation. The environmental pH is a key determinant regulating microbial growth and mineralization and then influences the structure of the final mineralized products of anaerobic iron-oxidizing bacteria. Freshwater lakes, in general, are neutral-pH environments. Understanding the effects of varying pH on the mineralization of iron-oxidizing bacteria under neutrophilic conditions could aid in finding out the optimal pH values that promote the coprecipitation of heavy metals. Here, two typical neutrophilic Fe(II)-oxidizing bacteria, the nitrate-reducing sp. strain BoFeN1 and the anoxygenic phototrophic strain SW2, were selected for studying how their growth and mineralization response to slight changes in circumneutral pH. By employing focused ion beam/scanning electron microscopy (FIB-SEM) and transmission electron microscopy (TEM), we examined the interplay between pH changes and anaerobic iron-oxidizing bacteria and observed that pH can significantly impact the microbial mineralization process and vice versa. Further, pH-dependent changes in the structure of mineralized products of bacterial iron oxidation were observed. Our study could provide mechanical insights into how to manipulate microbial iron oxidation for facilitating remediation of heavy metals in the environment.
在人类世，淡水湖泊常常受到各种重金属的污染。铁氧化微生物及其矿化产物可以与许多重金属共沉淀，包括铝、锌、铜、镉和铬。因此，微生物铁氧化对环境修复可产生深远影响。环境pH值是调节微生物生长和矿化的关键决定因素，进而影响厌氧铁氧化细菌最终矿化产物的结构。一般来说，淡水湖泊是中性pH环境。了解不同pH值对嗜中性条件下铁氧化细菌矿化的影响，有助于找出促进重金属共沉淀的最佳pH值。在此，选择了两种典型的嗜中性Fe（II）氧化细菌，即硝酸盐还原菌BoFeN1菌株和无氧光合菌SW2菌株，来研究它们的生长和矿化如何响应环境中性pH的微小变化。通过使用聚焦离子束/扫描电子显微镜（FIB-SEM）和透射电子显微镜（TEM），我们研究了pH变化与厌氧铁氧化细菌之间的相互作用，观察到pH会显著影响微生物矿化过程，反之亦然。此外，还观察到细菌铁氧化矿化产物结构的pH依赖性变化。我们的研究可为如何利用微生物铁氧化促进环境中重金属修复提供机理见解。
