Laboratorio Microbiología Molecular, Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile.
Departamento de Ciencias Nucleares, Comisión Chilena de Energía Nuclear, Santiago, Chile.
BMC Biotechnol. 2020 May 29;20(1):29. doi: 10.1186/s12896-020-00625-y.
The bacterial genus Exiguobacterium includes several species that inhabit environments with a wide range of temperature, salinity, and pH. This is why the microorganisms from this genus are known generically as polyextremophiles. Several environmental isolates have been explored and characterized for enzyme production as well as for bioremediation purposes. In this line, toxic metal(loid) reduction by these microorganisms represents an approach to decontaminate soluble metal ions via their transformation into less toxic, insoluble derivatives. Microbial-mediated metal(loid) reduction frequently results in the synthesis of nanoscale structures-nanostructures (NS) -. Thus, microorganisms could be used as an ecofriendly way to get NS.
We analyzed the tolerance of Exiguobacterium acetylicum MF03, E. aurantiacum MF06, and E. profundum MF08 to Silver (I), gold (III), and tellurium (IV) compounds. Specifically, we explored the ability of cell-free extracts from these bacteria to reduce these toxicants and synthesize NS in vitro, both in the presence or absence of oxygen. All isolates exhibited higher tolerance to these toxicants in anaerobiosis. While in the absence of oxygen they showed high tellurite- and silver-reducing activity at pH 9.0, whereas AuCl which was reduced at pH 7.0 in both conditions. Given these results, cell-free extracts were used to synthesize NS containing silver, gold or tellurium, characterizing their size, morphology and chemical composition. Silver and tellurium NS exhibited smaller size under anaerobiosis and their morphology was circular (silver NS), starred (tellurium NS) or amorphous (gold NS).
This nanostructure-synthesizing ability makes these isolates interesting candidates to get NS with biotechnological potential.
极端杆菌属（Exiguobacterium）包括了一些能在温度、盐度和 pH 值范围广泛的环境中生存的物种。这就是为什么这个属的微生物通常被称为多极端微生物。已经有一些环境分离株被探索和用于酶生产以及生物修复的目的。在这方面，这些微生物通过将可溶性金属离子转化为毒性较低的不溶性衍生物来还原有毒金属（类），这代表了一种去除污染的方法。微生物介导的金属（类）还原通常会导致纳米结构（NS）的合成。因此，微生物可以作为一种环保的方式来获得 NS。
我们分析了极端杆菌 MF03、MF06 和 MF08 对银（I）、金（III）和碲（IV）化合物的耐受性。具体来说，我们探索了这些细菌的无细胞提取物在有氧和无氧条件下还原这些有毒物质并在体外合成 NS 的能力。所有分离株在无氧条件下对这些有毒物质的耐受性更高。虽然在无氧条件下，它们在 pH 9.0 时表现出很高的亚碲酸盐和银还原活性，而 AuCl 在两种条件下均在 pH 7.0 时被还原。鉴于这些结果，我们使用无细胞提取物来合成含有银、金或碲的 NS，对其大小、形态和化学组成进行了表征。在无氧条件下，银和碲 NS 的尺寸较小，其形态为圆形（银 NS）、星形（碲 NS）或无定形（金 NS）。
这种合成 NS 的能力使这些分离株成为具有生物技术潜力的 NS 的有趣候选者。
