Impact of the Microbial Origin and Active Microenvironment on the Shape of Biogenic Elemental Selenium Nanomaterials

The shape of nanomaterials affects their colloidal properties, cellular uptake, and fate in the environment. The microbial origin and microenvironment can play a role in altering the shape of the nanomaterial. However, such studies have never been conducted. Here, we demonstrate that the selenium nanomaterials produced by Escherichia coli K-12 are stable and remain as BioSe-Nanospheres under thermophilic conditions, while those produced by anaerobic granular sludge transform to BioSe-Nanorods, due to a lower quantity of proteins coating these nanoparticles, which has been verified by proteomics analysis as well as using chemically synthesized selenium nanomaterials. Furthermore, the presence of Bacillus safensis JG-B5T transform the purified BioSe-Nanospheres produced by E. coli K-12 to BioSe-Nanorods, though they are not transformed in the absence of B. safensis JG-B5T. This is due to the production of peptidases by B. safensis JG-B5T that cleaves the protein coating the BioSe-Nanospheres produced by E. coli K-12, leading to their transformation to trigonal BioSe-Nanorods, which is the thermodynamically more stable state. These findings suggest that the fate of selenium and probably other redox-active elements released from the biological wastewater treatment units needs to be reevaluated and improved by including microbial criteria for better accuracy.纳米材料的形貌会影响其胶体特性、细胞摄取行为以及环境归趋。微生物来源与微环境可对纳米材料的形貌改变产生影响，然而此类研究此前尚未见报道。本研究证实，由大肠杆菌（Escherichia coli）K-12合成的硒纳米材料在嗜热条件下可保持稳定，以生物硒纳米球（BioSe-Nanospheres）形式存在；而由厌氧颗粒污泥合成的硒纳米材料则会转变为生物硒纳米棒（BioSe-Nanorods），这是由于包裹该类纳米颗粒的蛋白含量较低，该结论已通过蛋白质组学分析以及化学合成硒纳米材料实验得到验证。此外，当体系中存在沙福芽孢杆菌（Bacillus safensis）JG-B5T时，由大肠杆菌K-12合成的纯化生物硒纳米球可被转化为生物硒纳米棒；而在缺少该菌株的情况下，上述纳米球不会发生形貌转变。其背后机制为：沙福芽孢杆菌JG-B5T可分泌肽酶，裂解包裹大肠杆菌K-12合成的生物硒纳米球的蛋白层，促使其转变为三方晶系生物硒纳米棒——这是热力学上更稳定的物相。本研究结果表明，针对生物污水处理单元释放的硒以及其他潜在氧化还原活性元素，需纳入微生物相关评判标准以提升评估准确性，对其环境归趋进行重新评估与完善。