耐硒芽孢杆菌的筛选及其亚硒酸盐还原机制的探究

微生物能将氧化形态的有毒硒转化为无毒的纳米硒（SeNPs），这种“绿色合成”方式在功能性产品开发、环境治理和医疗等方面的应用潜力巨大。本文从长期施加硒肥的大豆种植基地中筛选出菌株F4，对该菌株进行耐硒能力测定、鉴定分类、生长还原动力学分析，并通过体外还原试验初步探究亚硒酸钠的还原机理。结果表明:该菌属于高山芽孢杆菌（Bacillus altitudinis），在浓度为50 mmoL/L亚硒酸钠平板中，菌株菌落存活率为37.08%，对亚硒酸钠的耐受能力可高达250 mmoL/L。在含硒培养基中的还原过程发现，菌株在前期6~14 h先生长然后在对数期中后期14~48 h对亚硒酸钠进行还原，并在稳定时期产生红色沉淀。体外还原定位试验反应体系在33 ℃下孵育24 h后，在培养上清和胞外多糖中观察到反应活性，添加还原型辅酶ⅠNADH下细胞质有略微变化。该芽孢杆菌可作为生产红色纳米硒的菌株，可为硒的生物转化提供参考。

Screening of Selenium-tolerant Bacillus and Exploration of Its Selenite Reduction Mechanism

Microbes can convert oxidized toxic selenium into non-toxic selenium nanoparticles(SeNPs), this "green synthesis" method has great application potential in functional product development, environmental governance, and medical treatment. In this study, strain F4 was isolated from soybean planting bases with long-term application of selenium fertilizer. It was tested for selenium tolerance, identification classification, growth reduction kinetic analysis. In order to understand the mechanism of selenite reduction and elemental selenium formation, as well as its intracellular and extracellular distribution, the location of the selenite reduction reaction in bacterial culture were studied by in vitro reduction localization experiments. The results showed that, the strain F4 belonged to Bacillus altitudinis. When the culture was supplemented of 50 mmoL/L sodium selenite, the bacterial colony survival rate was 37.08%, and the tolerance to sodium selenite was as high as 250 mmoL/L. In the selenium-containing medium, the strain grew then reduced sodium selenite in the middle and late logarithmic phase, and produces a red precipitate in the stable phase. After incubating the reaction system for the in vitro reduction localization test at 33 ℃ for 24 h, reactivity was observed in the culture supernatant and extracellular polysaccharide, and the cytoplasm changed slightly with the addition of NADH. This bacillus could be used as a strain for producing red nano-selenium. It could provide a reference for the biotransformation of selenium.