Zhang Xuexia, Jia Yongfeng, Wang Xin, Xu Liying
Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
J Environ Sci (China). 2008;20(12):1501-7. doi: 10.1016/s1001-0742(08)62556-5.
Microbial reduction of As(V) (i.e., arsenate) plays an important role in arsenic (As) mobilization in aqueous environment. In this study, we investigated As(V) reduction characteristics of the bacteria enriched from the arsenic-contaminated soil at an abandoned smelter site. It was found that As(V) was completely reduced to As(III) (i.e., arsenite) in 21 h. After 3-d incubation, a yellow solid was precipitated and the concentration of As(III) decreased sharply. After 150 h incubation, ca. 65% of soluble arsenic was removed from the solution. The analysis of the precipitate by scanning electron microscopy and energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD) revealed that the main component was crystalline arsenic sulfide (AsS). Microbial mediated reduction and mobilization of adsorbed As(V) on ferric hydroxide was also examined. In the microcosm slurry experiment, ca. 53% of the adsorbed As(V) was reduced to As(III) by the bacteria, which resulted in an appreciable release of arsenic into aqueous phase. The released arsenic was present predominantly as As(III). The microbial diversity was analyzed by 16S rDNA-dependent molecular phylogeny. A near-full-length 16S rDNA gene clone library was constructed. The 197 clones were analyzed using RFLP (restriction fragment length polymorphism) and 72 OTUs were obtained, which contributed 51% of the content for total clone number in six OTUs. Six bacterial clones in these six OTUs were selected for sequencing and the sequenced clones were found to belong to the group Caloramator, Clostridium, and Bacillus.
微生物对五价砷（即砷酸盐）的还原在水环境中砷的迁移过程中起着重要作用。在本研究中，我们调查了从一个废弃冶炼厂受砷污染土壤中富集的细菌对五价砷的还原特性。结果发现，五价砷在21小时内完全还原为三价砷（即亚砷酸盐）。经过3天的培养，沉淀出一种黄色固体，三价砷的浓度急剧下降。培养150小时后，约65%的可溶性砷从溶液中去除。通过扫描电子显微镜和能量色散光谱仪（SEM-EDS）以及X射线衍射（XRD）对沉淀物进行分析，结果表明其主要成分是结晶硫化砷（AsS）。我们还研究了微生物介导的氢氧化铁吸附态五价砷的还原和迁移。在微观泥浆实验中，约53%的吸附态五价砷被细菌还原为三价砷，这导致砷大量释放到水相中。释放出的砷主要以三价砷的形式存在。通过基于16S rDNA的分子系统发育分析微生物多样性。构建了一个近全长的16S rDNA基因克隆文库。使用限制性片段长度多态性（RFLP）对197个克隆进行分析，获得了72个操作分类单元（OTU），其中6个OTU占总克隆数的51%。从这6个OTU中选择了6个细菌克隆进行测序，发现测序的克隆属于热厌氧杆菌属、梭菌属和芽孢杆菌属。
