节杆菌FX8的分离筛选及其生物成矿除砷

【背景】砷（arsenic，As）是一种剧毒的类金属，水体砷污染问题日益突出，严重威胁人类健康，开发高效除砷方法迫在眉睫。【目的】吸附法是目前除砷应用最多的方法之一，对从铁矿表层土壤分离得到的一株铁氧化菌FX8进行研究，以期通过其氧化Fe （II）生成的铁矿物作为吸附剂而去除砷。【方法】通过形态学特征、生理生化特性、全基因组测序分析对菌株进行鉴定，采用邻菲罗啉分光光度法测定总Fe和Fe （II），利用X射线衍射（X-ray diffraction，XRD）、X射线光电子能谱（X-ray photoelectron spectroscopy，XPS）和能量色散谱（energy dispersive spectrometer，EDS）对铁氧化物沉淀进行分析，采用高压液相色谱-氢化物发生-原子荧光光谱测定总As。【结果】菌株FX8为革兰氏阳性、好氧，其菌落为圆形、乳白色，扫描电镜（scanning electron microscope，SEM）镜检细胞为杆状，大小为（0.5-2.5）μm×（0.13-0.25）μm，可归为节杆菌属（Arthrobacter）。菌株FX8能够氧化Fe （II）并生成铁氧化物沉淀，该沉淀为一种无定形的Fe （III）矿物，其结晶性差且含有大量生物杂质，并且通过产生胞外酶氧化Fe （II）。菌株FX8在28℃、150 r/min条件下，在加As （III）和As （V）体系中，48 h内总Fe的去除率均为100%，而对应的总As去除率分别为99.54%和99.86%；在As （III）和As （V）体系中加入菌株FX8的胞外粗酶液，2 h内总Fe的去除率均为100%，相应的总As去除率为99.45%和100%。【结论】菌株FX8是一株铁氧化菌，利用其胞外粗酶液生物矿化铁除砷的效果优于菌株-砷共培养，本研究可为水体砷污染的高效生物修复提供新的生物材料及理论参考。

Isolation of Arthrobacter FX8 capable of removing arsenic by biomineralization

[Background] The contamination of arsenic (As), a highly toxic metalloid, in water is aggravating, which threatens human health. The common method used for removing As is adsorption, and it is urgent to develop efficient As removal methods. [Objective] To characterize an iron-oxidizing bacterial strain FX8 isolated from the surface soil of iron ore, so as to use the iron mineral (adsorbent) produced by the strain via oxidizing Fe(II) for removing As. [Methods] The strain was identified based on morphological, physiological, and biochemical characteristics and genome-wide sequencing evidence. The concentrations of total Fe and Fe(II) were determined by phenanthroline spectrophotometry. The iron oxide precipitates were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive spectrometer. The concentration of total As was determined by high performance liquid chromatography in combination with hydride generation and atomic fluorescence spectroscopy. [Results] Strain FX8 was Gram-positive and aerobic, with while and round colonies. Its cells were rod-shaped with the size of (0.5-2.5) μm×(0.13-0.25)μm. FX8 was identified as a strain of Arthrobacter. It could oxidize Fe(II) to generate iron oxide precipitates which were an amorphous Fe(III) mineral with poor crystallinity and a large amount of biological impurities. Strain FX8 oxidized Fe(II) by producing extracellular enzymes. The strain cultured with As(III) or As(V) at 28℃ and 150 r/min showed the total Fe removal rates of 100% in 48 h and the corresponding total As removal rates of 99.54% and 99.86%, respectively. When the extracellular enzyme liquid of strain FX8 was added into the As(III) or As(V) system, the total Fe removal rates reached 100% in 2 h, and the corresponding total As removal rates were 99.45% and 100%, respectively. [Conclusion] Strain FX8 is an iron-oxidizing bacterium, and the iron biomineralization with its extracellular enzyme liquid outperforms strain-arsenic coculture in the removal of As. The findings provide new biomaterials and theoretical references for the efficient remediation of As-contaminated water.