Figueroa Maximiliano, Fernandez Valentina, Arenas-Salinas Mauricio, Ahumada Diego, Muñoz-Villagrán Claudia, Cornejo Fabián, Vargas Esteban, Latorre Mauricio, Morales Eduardo, Vásquez Claudio, Arenas Felipe
Laboratorio Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
Centro de Bioinformática y Simulación Molecular, Universidad de Talca, Talca, Chile.
Front Microbiol. 2018 May 15;9:959. doi: 10.3389/fmicb.2018.00959. eCollection 2018.
Microbes are suitable candidates to recover and decontaminate different environments from soluble metal ions, either via reduction or precipitation to generate insoluble, non-toxic derivatives. In general, microorganisms reduce toxic metal ions generating nanostructures (NS), which display great applicability in biotechnological processes. Since the molecular bases of bacterial reduction are still unknown, the search for new -environmentally safe and less expensive- methods to synthesize NS have made biological systems attractive candidates. Here, 47 microorganisms isolated from a number of environmental samples were analyzed for their tolerance or sensitivity to 19 metal(loid)s. Ten of them were highly tolerant to some of them and were assessed for their ability to reduce these toxicants . All isolates were analyzed by 16S rRNA gene sequencing, fatty acids composition, biochemical tests and electron microscopy. Results showed that they belong to the , and genera. Most strains displayed metal(loid)-reducing activity using either NADH or NADPH as cofactor. While showed the highest tellurite ( ) and tetrachloro aurate ( ) reducing activity, and exhibited selenite ( ) and silver (Ag) reducing activity, respectively. Based on these results, we used these bacteria to synthetize, Te, Se, Au, and Ag-containing nanostructures. On the other hand, we also used purified glutathione reductase to synthesize Te-, Ag-, and Se-containing NS, whose morphology, size, composition, and chemical composition were evaluated. Finally, we assessed the putative anti-bacterial activity exhibited by the synthesized NS: Te-containing NS were more effective than Au-NS in inhibiting and growth. Aerobically synthesized TeNS using MF09 crude extracts showed MICs of 45- and 66- μg/ml for and , respectively. Similar MIC values (40 and 82 μg/ml, respectively) were observed for TeNS generated using crude extracts from -overexpressing . In turn, AuNS MICs for and were 64- and 68- μg/ml, respectively.
微生物是从可溶性金属离子中恢复和净化不同环境的合适候选者，它们可以通过还原或沉淀生成不溶性、无毒衍生物。一般来说，微生物会还原有毒金属离子生成纳米结构（NS），这些纳米结构在生物技术过程中具有很大的适用性。由于细菌还原的分子基础仍然未知，寻找新的（环境安全且成本较低的）合成纳米结构的方法使生物系统成为有吸引力的候选者。在这里，对从多个环境样本中分离出的47种微生物进行了分析，以检测它们对19种金属（类金属）的耐受性或敏感性。其中有10种对其中一些金属具有高度耐受性，并评估了它们还原这些有毒物质的能力。所有分离株都通过16S rRNA基因测序、脂肪酸组成、生化测试和电子显微镜进行了分析。结果表明它们属于芽孢杆菌属、假单胞菌属和葡萄球菌属。大多数菌株使用NADH或NADPH作为辅因子表现出金属（类金属）还原活性。虽然MF09显示出最高的亚碲酸盐（TeO₃²⁻）和四氯金酸盐（HAuCl₄）还原活性，但MF04和MF06分别表现出亚硒酸盐（SeO₃²⁻）和银（Ag）还原活性。基于这些结果，我们利用这些细菌合成了含碲（Te）、硒（Se）、金（Au）和银（Ag）的纳米结构。另一方面，我们还使用纯化的谷胱甘肽还原酶合成了含碲、银和硒的纳米结构，并对其形态、大小、组成和化学组成进行了评估。最后，我们评估了合成的纳米结构所表现出的假定抗菌活性：含碲纳米结构在抑制金黄色葡萄球菌和大肠杆菌生长方面比含金纳米结构更有效。使用MF09粗提物需氧合成的碲纳米结构对金黄色葡萄球菌和大肠杆菌的最低抑菌浓度（MIC）分别为45和66 μg/ml。使用来自谷胱甘肽还原酶过表达菌株的粗提物生成的碲纳米结构也观察到类似的MIC值（分别为40和82 μg/ml）。相应地，含金纳米结构对金黄色葡萄球菌和大肠杆菌的MIC分别为64和68 μg/ml。
