Selenite reduction by the rhizobacterium Azospirillum brasilense, synthesis of extracellular selenium nanoparticles and their characterization,New Biotechnology

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Selenite reduction by the rhizobacterium Azospirillum brasilense, synthesis of extracellular selenium nanoparticles and their characterization
New Biotechnology ( IF 4.5 ) Pub Date : 2020-09-01 , DOI: 10.1016/j.nbt.2020.02.003
Anna V Tugarova ₁ , Polina V Mamchenkova ₁ , Vitaly A Khanadeev ₂ , Alexander A Kamnev ₁

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Microbial reduction of selenium oxyanions has attracted attention in recent years. In this study, an original and simple method for the synthesis of extracellular selenium nanoparticles (Se NPs) of relatively uniform size has been developed using strains Sp7 and Sp245 of the ubiquitous plant-growth promoting rhizobacterium Azospirillum brasilense, both capable of selenite (SeO32-) reduction. In addition, a reliable purification protocol for the recovery of the Se NPs has been perfected, which could be applied with minor modifications to cultures of other microbial species. Importantly, it was found that, by changing the conditions of bacterial reduction of selenite, extracellularly localized Se NPs can be obtained using bacteria which would otherwise produce intracellular Se NPs. In particular, bacterial cultures grown up to the end of the logarithmic growth phase, washed free of culture medium and then incubated with selenite, were used to obtain extracellular Se NPs. Their sizes depended on the initial selenite concentration (∼25-80 nm in diameter at 50-10 mM selenite, respectively). The Se NPs obtained were characterized by transmission electron microscopy (TEM), dynamic light scattering, and Raman and UV-visible spectroscopies. Their zeta potential was found to be negative (ca. minus 21-24 mV). Bacterial selenite reduction was also studied in the presence of the efflux pump inhibitor carbonyl cyanide m-chlorophenylhydrazone (CCCP). In this case, TEM indicated the formation only of intracellular selenium crystallites. The data show that the formation of extracellular Se NPs requires normal bacterial metabolic activity, while CCCP evidently blocks the membrane export of Se° nuclei.

中文翻译：

巴西固螺菌还原亚硒酸盐、胞外硒纳米颗粒的合成及其表征

近年来，硒氧阴离子的微生物还原引起了人们的关注。在这项研究中，使用普遍存在的促进植物生长的巴西固氮螺菌的 Sp7 和 Sp245 菌株开发了一种合成尺寸相对均匀的细胞外硒纳米颗粒 (Se NPs) 的原始而简单的方法，两者都能够产生亚硒酸盐 (SeO32- ）减少。此外，还完善了用于回收硒纳米颗粒的可靠纯化方案，只需稍加修改即可应用于其他微生物物种的培养。重要的是，发现通过改变亚硒酸盐的细菌还原条件，可以使用细菌获得细胞外定位的硒纳米颗粒，否则会产生细胞内硒纳米颗粒。特别是，细菌培养物生长到对数生长期结束，洗掉培养基，然后与亚硒酸盐一起孵育，用于获得细胞外硒纳米颗粒。它们的大小取决于初始亚硒酸盐浓度（直径分别为 25-80 nm 和 50-10 mM 亚硒酸盐）。获得的硒纳米颗粒通过透射电子显微镜 (TEM)、动态光散射以及拉曼和紫外可见光谱进行表征。发现它们的 zeta 电位为负值（约负 21-24 mV）。在外排泵抑制剂羰基氰化物间氯苯腙 (CCCP) 存在下，还研究了细菌亚硒酸盐的还原。在这种情况下，TEM 表明仅形成细胞内硒微晶。数据表明细胞外Se NPs的形成需要正常的细菌代谢活动，

更新日期：2020-09-01

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