College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
Beijing Key Laboratory of Biodiversity and Organic Farming, China Agricultural University, Beijing, 100193, China.
Appl Microbiol Biotechnol. 2018 Jul;102(14):6191-6205. doi: 10.1007/s00253-018-9060-z. Epub 2018 May 27.
Rahnella aquatilis HX2 (proteobacteria) shows tolerance to selenium (Se). The minimum inhibitory concentrations of selenomethionine (Se-Met), selenite [Se (IV)], and selenate [Se (VI)] to HX2 are 4.0, 85.0, and 590.0 mM, respectively. HX2 shows the ability to reduce Se (IV) and Se (VI) to elemental Se nanoparticles (SeNPs). The maximum production of SeNPs by HX2 strain is 1.99 and 3.85 mM in Luria-Bertani (LB) broth with 5 mM Se (IV) and 10 mM Se (VI), respectively. The morphology of SeNPs and cells were observed by transmission electron microscope, environmental scanning electron microscope, and selected area electric diffraction detector. Spherical SeNPs with amorphous structure were found in the cytoplasm, membrane, and exterior of cells. Morphological variations of the cell membrane were further confirmed by the release of cellular materials absorbed at 260 nm. Flagella were inhibited and cell sizes were 1.8-, 1.6-, and 1.2-fold increases with the Se-Met, Se (VI), and Se (IV) treatments, respectively. The real-time quantitative PCR analysis indicated that some of the genes controlling Se metabolism or cell morphology, including cysA, cysP, rodA, ZntA, and ada, were significantly upregulated, while grxA, fliO, flgE, and fliC genes were significantly downregulated in those Se treatments. This study provided novel valuable information concerning the cell morphology along with biological synthesis process of SeNPs in R. aquatilis and demonstrated that the strain HX2 could be applied in both biosynthesis of SeNPs and in management of environmental Se pollution.
水生拉恩氏菌 HX2（变形菌门）对硒（Se）具有耐受性。硒代蛋氨酸（Se-Met）、亚硒酸盐[Se（IV）]和硒酸盐[Se（VI）]对 HX2 的最小抑菌浓度分别为 4.0、85.0 和 590.0 mM。HX2 表现出将 Se（IV）和 Se（VI）还原为元素硒纳米颗粒（SeNPs）的能力。HX2 菌株在含 5 mM Se（IV）和 10 mM Se（VI）的 LB 肉汤中分别最大生成 1.99 和 3.85 mM 的 SeNPs。通过透射电子显微镜、环境扫描电子显微镜和选区电子衍射探测器观察 SeNPs 和细胞的形态。在细胞质、细胞膜和细胞外发现了具有非晶态结构的球形 SeNPs。细胞膜的形态变化进一步通过吸收在 260 nm 处的细胞物质的释放得到证实。鞭毛受到抑制，细胞大小分别增加了 1.8、1.6 和 1.2 倍，用 Se-Met、Se（VI）和 Se（IV）处理。实时定量 PCR 分析表明，一些控制硒代谢或细胞形态的基因，包括 cysA、cysP、rodA、ZntA 和 ada，显著上调，而 grxA、fliO、flgE 和 fliC 基因在这些 Se 处理中显著下调。本研究为水生拉恩氏菌中 SeNPs 的细胞形态和生物合成过程提供了新的有价值的信息，并表明菌株 HX2 可应用于 SeNPs 的生物合成和环境 Se 污染的管理。
