河套平原强还原高砷地下水系统微生物分子生态学研究
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摘要
原生高砷地下水是当今国际社会面临的最严重的环境问题之一。目前,全世界有超过1.4亿人受到高砷地下水的威胁,高砷地下水遍及孟加拉国、印度、越南、智利、阿根廷、日本、美国和中国等国家。在我国,高砷地下水主要集中在新疆、山西、内蒙古、贵州、台湾等地,受影响人口高达300万人。砷是一种严重的致癌物质,长期摄入高砷地下水会导致诸多慢性疾病和癌症,如皮肤色素沉着、角膜炎、心血管疾病,甚至皮肤癌、肝癌、肾癌等,影响十分恶劣。当今国际社会对原生高砷地下水的研究主要集中在砷的水文地球化学、矿物学、沉积环境方面。已有研究表明,地下水和沉积物环境中砷的迁移转化是一系列复杂的微生物参与和地球化学过程共同作用的结果。微生物所具有的氧化还原能力和对敏感元素的抗性,使它们成为地质环境中一种重要的媒介物,影响着元素的迁移转化富集过程。目前,关于砷的释放机制主要有三种：黄铁矿的氧化、铁的羟基氧化物的还原性溶解和铁锰氧化物的阳离子竞争性吸附,微生物可能参与所有这些过程。然而目前国内外对微生物参与下砷的迁移与转化机理方面的研究还处于初步阶段,对高砷含水层中哪些微生物发挥关键作用、不同环境介质中微生物作用有无不同等问题还尚不清楚。因此,对高砷含水层中的微生物群落结构和多样性以及功能微生物群落进行研究,对理解微生物对高砷地下水中砷迁移转化的机理具有重要意义。
本研究以我国原生高砷地下水典型地区内蒙古河套平原杭锦后旗为研究区,将地球化学分析与先进的微生物分子生态学手段和方法相结合,通过研究高砷地下水和沉积物中的微生物多样性及其群落结构特征,分析强还原高砷地下水中的功能微生物群落,并与地球化学参数相结合,探讨微生物群落在高砷地下水迁移富集过程中的作用机理。研究的主要成果如下：
1.河套平原杭锦后旗典型强还原条件下高砷地下水和沉积物的地球化学特征。
以杭锦后旗作为典型研究区,通过大量野外调查和前期研究总结,有针对性的采集了典型高砷地下水样品21件和3个钻孔(包括2个高砷钻孔和1个低砷钻孔)的垂向沉积物样品32件,分析了高砷地下水样品中水化学环境与砷浓度之间的关系,刻画了沉积物样品中砷(形态)、铁、硫、TOC等的垂向分布特征。研究区多数高砷地下水的氧化还原电位为负值,pH为近中性或弱碱性。样品总砷和三价砷的浓度范围分别为65.6-1088.7μg/L和14.5-560.3μg/L,其中超过半数样品的三价砷浓度高于五价砷浓度。三价砷浓度和总砷浓度之间呈现出良好的线性相关关系。总铁浓度变化为107-2257μg/L。甲烷浓度随着总砷浓度的增加而升高,最高值可达568.20μg/L。所有样品的硝酸盐含量都非常低,而硫酸盐含量只在总砷含量非常低时显著增高。样品中的TOC浓度为1.9-11.9mg/L。TOC含量以及Fe(Ⅱ)/Fe(Ⅲ)均与总砷浓度呈现出正相关关系,而硫酸根含量则与总砷浓度呈指数负相关。多数高砷地下水样品具有高浓度的三价砷、TOC、Fe(Ⅱ)/Fe(Ⅲ)和低浓度的硫酸根、硝酸根。
高砷沉积物样品中砷含量为33.6-77.6mg/kg,而对照低砷沉积物样品的砷含量仅为1.5-5.8mg/kg。所有样品中均没有检测到一甲基砷和二甲基砷。在高砷沉积物钻孔中,三价砷的含量随深度而增加,但是所有样品均以五价砷为主。高砷沉积物中亚铁和三价铁的含量分别为0.05-7.01g/kg和0.38-5.29g/kg,亚铁和总铁的比值随着深度的增加而增大。总铁与总砷呈现出相同的变化趋势,与已有的研究结果一致。TOC含量为0.002-1.854wt.%,与总砷含量呈正相关关系。高砷沉积物主要出现在粘土和亚粘土样品中,这些样品同时表现出高浓度的硫、铁和TOC含量。
2.浅层强还原高砷地下水系统中的微生物群落多样性和群落结构的空间变化规律。
在以上研究结果的基础上,选取典型强还原区高砷地下水和沉积物样品,采用PCR-DGGE指纹图谱和16S rRNA基因克隆文库、Illumina Miseq测序等微生物分子生态学研究方法,并结合样品中砷、铁、硫等的分布特征,研究高砷地下水系统中的原位微生物群落在地下水和沉积物中的空间分布特征及多样性。
沉积物样品的PCR-DGGE指纹图谱分析结果表明,高砷沉积物中微生物群落结构与低砷沉积物显著不同。在图谱中,与假单胞菌属和不动杆菌属有关的条带随着总砷浓度的降低而逐渐淡出,而与硫杆菌属相关的条带随着硫酸根浓度的增加而增强。对高砷沉积物钻孔样品中微生物群落的系统发育关系进行构建,高砷沉积物中主要包括四类微生物：α-,β-,γ-变形菌和厚壁菌门。其中一些DGGE条带序列与假单胞菌、短波单胞菌和八叠球菌等菌有关,已有研究证明这些细菌种群具有很强的砷抗性。另一些条带序列与假单胞菌和硫杆菌十分相似,这两种细菌与淡水或土壤系统中的硫氧化和反硝化作用紧密相关。低砷沉积物样品中的优势种群主要与寒冷环境如海洋沉积物和永冻土中的微生物相似。研究发现,低砷沉积物样品的微生物群落多样性高于高砷沉积物样品,这与对孟加拉国含水层的研究结果一致。高砷沉积物样品的16S rRNA基因克隆文库研究结果发现,河套平原高砷沉积物中以β-变形菌为主,这与之前对高砷河床沉积物开展的研究结果相似。其中,超过70%的克隆子与具有硫氧化和铁氧化功能的硫杆菌高度相似。此外,假单胞菌、短波单胞菌和嗜氢菌属也是高砷沉积物中的优势种群。本研究组在已有的研究中发现在采样点有大量含砷黄铁矿的存在,推测在微生物群落如硫杆菌的作用下,含砷黄铁矿的氧化可能导致砷、硫和铁的释放,五价砷酸盐在氧化性矿物表面富集。此后,被吸附的五价砷被还原为在矿物表面吸附性较差的三价砷进入地下水系统。这可能是沉积物中以As(V)为主而地下水中则以As(Ⅲ)为主的原因。
三个典型水样的16S rRNA基因克隆文库的研究结果表明：高砷地下水样品中的细菌群落分为12类,包括α-、β-、δ-、ε-和γ-变形菌门、绿细菌门、拟杆菌门、厚壁菌门、绿弯菌门、放线菌门以及异常球菌-栖热菌门。其中三价砷占总砷比例最大的样品呈现出最高的群落多样性。此外,在纲的分类水平上,该样品以α-变形菌纲和β-变形菌纲为主,不同于砷含量最低和砷含量最高的两个样品。但是在属的分类水平上,三个样品的优势种群均属于不动杆菌属和假单胞菌属。总体来说,高砷地下水中的优势细菌群落包括不动杆菌属,假单胞菌属,短波单胞菌属,嗜酸菌属和水杆菌属。同样地,对高砷地下水中古菌群落的分析结果显示,砷含量最低的样品古菌群落多样性最高,说明砷的毒性可能降低高砷地下水中古菌的多样性。高砷地下水中古菌群落包括奇古菌门、泉古菌门和广古菌门。其中,奇古菌门是一类新分类的古菌,包括所有已知的氨氧化古菌。研究中与奇古菌门相关的条带亮度随着样品硝酸根浓度的降低和砷浓度的增加而逐渐减弱。文库分析结果显示高砷地下水中古菌的优势群落为甲烷丝状菌(属于广古菌门),Nitrosophaera(属于奇古菌门)和热变形菌(属于泉古菌门)。热变形菌可以利用H2作为电子供体进行硫还原。这些结果揭示出高砷地下水中微生物作用下的氨氧化和硫氧化反应的存在。
高砷地下水Illumina MiSeq测序结果表明水化参数不同的样品的微生物群落也显著不同。多数地下水中的优势种群包括不动杆菌、Rheinheimera、假单胞菌、Methylotenera、水杆菌、噬氢菌、泉发菌和LCP-6等,与文库分析结果基本一致。但在文库分析时未发现Rheinheimera,Methyloteenera,泉发菌和LCP-6,表明文库分析和高通量测序之间可能存在一定的偏差。研究发现,造成高砷地下水和低砷地下水差异性的前十位微生物种群包括不动杆菌、假单胞菌、Alishewanella、嗜冷菌、Rheinheimera、水杆菌、丛毛单胞菌和披毛菌。统计学分析结果表明,砷含量不同的地下水样品,其他的水化参数也显著不同。此外,高砷地下水与低砷地下水中的微生物优势群落显著不同,除了砷浓度主要影响外,其他环境因子也可能导致群落构成的不同。
通过对同一采样点的沉积物和地下水样品的微生物群落对比发现,高砷沉积物中的微生物群落与高砷地下水中的微生物群落显著不同。沉积物和地下水中砷形态的不同分配,以及不同的微生物群落构成,都表明微生物作用下的沉积物和地下水中砷的迁移转化机制可能不同。
3.强还原高砷地下水中的功能微生物群落
研究高砷地下水环境中功能群落的多样性和丰度,能更好地理解微生物生态和与高砷环境相关的微生物作用。前面的研究结果表明,河套平原高砷地下水处于强还原条件下,并伴有高浓度的砷、TOC和甲烷以及低浓度的硫酸盐和硝酸盐。因此,本论文通过对微生物功能基因的研究,对河套平原高砷地下水中的硫酸盐还原菌、产甲烷菌、砷氧化菌和砷还原菌的群落结构特征与丰富度进行了分析。
通过对细菌砷氧化基因aioA的基因文库分析,发现河套地区高砷地下水中的砷氧化菌均属于变形菌门,包括α-、β和γ-变形菌。其中,β-变形菌纲的克隆子均属于伯克氏菌目,与Rhodoferax ferrireducens、纤毛菌属和嗜酸菌属的细菌高度相似。Rhodoferax ferrireducens是一类可以进行异化铁还原的厌氧菌。纤毛菌属和嗜酸菌属的细菌曾从砷污染的沉积物或者含砷尾矿点分离得到。属于γ-变形菌纲的克隆与假单胞菌属和不动杆菌属的细菌相似,这与高砷地下水中的微生物群落中大量存在假单胞菌和不动杆菌的结果一致。属于α-变形菌纲的克隆与根瘤菌目的细菌,包括自养黄杆菌、慢生根瘤菌、氨基杆菌、Bosea sp和汉氏硝化菌等相似。前人研究表明这些种属的细菌大部分来自从砷污染的土壤。河套高砷地下水中砷氧化菌优势群落包括Rhodoferax ferrireducens、纤毛菌、嗜酸菌、假单胞菌和不动杆菌。高砷地下水中的砷还原群落主要分布在δ-变形菌、β-变形菌、产金菌门和厚壁菌门以及不可培养未鉴定的群落,其中不可培养未鉴定的种群占到约三分之一。优势群落包括地杆菌、脱硫芽孢弯菌、产金菌和Desulfurispirillum,这些菌落多是能进行异化砷酸盐还原或者硫氧化的细菌。而未培养的群落与在西孟加拉和美国北犹他州高砷沉积物或地下水中发现的不可培养异化砷还原菌相似度较高。河套平原高砷地下水中砷还原菌和砷氧化菌的同时存在,也说明了地下水系统中与微生物作用有关的砷迁移转化的复杂性。
对18个高砷地下水样品中的产甲烷菌进行分析,结果表明mcrA基因的丰度为3.01×103到3.80×106拷贝/L,在甲烷含量高的样品中丰度更大。mcrA基因占总古菌的比例(相对丰度)为0.0-30.2%。研究发现,mcrA基因的相对丰度与样品的总砷以及亚铁含量呈正相关,这可能预示产甲烷菌在砷含量高的样品中更加丰富,并且与含砷矿物的溶解有关。此外,mcrA基因的相对丰度与样品的硫酸盐含量呈明显的负指数相关,这与已有研究结果中提出的高砷地下水中硫酸盐的消耗可以加速甲烷的积累一致。克隆文库结果显示,高砷地下水中的甲烷菌包括甲烷微菌纲、甲烷杆菌纲和不可培养群落,其中83%克隆子属于甲烷微菌纲,包括甲烷微菌目和甲烷八叠球菌目。这些种属的产甲烷菌多分离自泥炭沼泽、消化淤泥、永冻土和金属污染的沉积物。此外,研究中发现一些克隆序列与已知的mcrA基因序列相似度极低,表明高砷地下水中可能有新的产甲烷类群的存在。
对21个高砷地下水中的硫酸盐还原菌功能基因dsrB进行分析,发现高砷地下水中细菌16S基因和dsrB基因的丰度分别为8.74×106-4.12×109拷贝/L和0-4.9×106拷贝几。其中有7个样品的dsrB相对丰度超过0.1%,最高为2.1%。dsrB基因丰度与地下水样品的总砷浓度呈正指数相关关系,可以推测硫酸盐还原与砷和铁的还原可能同时发生。DGGE指纹图谱分析结果显示,高砷地下水中的硫酸盐还原菌属于厚壁菌门和δ-变形菌,优势群落包括脱硫肠状菌、脱硫叶菌、脱硫叠球菌和Desulfobacca。之前已有研究在砷污染环境中发现脱硫肠状菌能够将砷作为电子受体进行代谢。
High arsenic (As) groundwater has become one of the most serious environmental problems nowadays, threatening the lives of more than140million people. At present, high As groundwater has been found in more than17Countries including Bangladesh, India, Vietnam, Argentina, Chile, Japan, USA and China. In China, high As groundwater are mainly distributed in Xinjiang, Shanxi, Inner Mongolia, Taiwan and Guizhou, with more than3million people under threat. Long term intake of high As groundwater can cause many chronic diseases and severe cancers such as vascular disease, skin cancer, respiration and heart cancer. Nowadays, many studies have been conducted concerning geogenic As groundwater and focused on hydrogeochemistry, mineralogy and deposit conditions. Previous studies indicated that As release and mobilization in aquifers are integrated results of series of microbially mediated reactions and geochemical processes. Microorganisms as one kind of important geological mediators, their resistance, and oxidizing or reducing capacity can allow them to function and affect mobilization of absorbed As. At present, three mechanisms of As enrichment in groundwater systems have been proposed in microbes can play important roles:oxidation of As-rich sulfide mineral, reductive dissolution of Fe(III) oxyhydroxides, and dissimilatory reduction of As. Therefore, to better understand the microbially mediated mechanism of As mobilization and release, it is worthy of studying the in situ microbial community structures and diversities and the functional microbial populations in high As aquifers.
In this study, microbially mediated As release and mobilization in strongly reducing aquifers of Hetao Plain were studied using both geochemical and microbial molecular methods, to analyze the geochemistry of groundwater and aquifer sediments, to investigate microbial community structure and diversity in sediments and groundwater with different geochemical characteristics, and to explore functional microbial communities in strongly reducing As groundwater. The main results are as follows:
1. Geochemical characteristics of high As groundwaters and sediments in Hetao Plain.
Twenty-one high As groundwater samples and thirty-two sediment samples from three boreholes which included two high As borehole and one control borehole were collected for geochemical analysis including As speciation, Fe, S and TOC. Most groundwater samples had negative Eh values under near neutral or weakly alkaline conditions. Concentrations of total As and As(Ⅲ) varied in the range of65.6-1088.7μg/L and14.5-560.3μg/L, respectively. As(Ⅲ) concentrations in more than half of the samples were higher than As(V) and concentrations of As(Ⅲ) and total As showed positive linear relationship. Total iron concentrations changed between107μg/L and2257μg/L. Methane concentrations increased with total As concentrations, with the highest value of568.20μg/L. Sulfate concentrations were relatively low in all samples while distinctly elevated only when total As concentrations were low. TOC concentrations ranged from1.9mg/L to11.9mg/L. TOC concentrations and Fe(Ⅱ)/Fe(Ⅲ) values showed positive correlation with total As concentrations, while sulfate concentrations presented negative exponential correlation with total As. Most of high As groundwaters were characterized with high concentrations of As(Ⅲ), TOC, Fe(Ⅱ)/Fe(Ⅲ) and low concentrations of sulfate and nitrate.
Arsenic contents in high As sediments varied between33.6mg/kg and77.6mg/kg while in low As sediments ranged from1.5mg/kg to5.8mg/kg. MMAV and DMAV were under the detection limits in all sediment samples. In high As boreholes, As(Ⅲ) contents increased with depth, but As(Ⅴ) dominated in all samples. The concentrations of Fe(Ⅱ) and Fe(Ⅲ) in the high As sediments lay in the range0.05-7.01g/kg and0.38-5.29g/kg, the ratios of Fe(Ⅱ) to total Fe increased with depth. Positive correlation was found between total Fe and total As, which was consistent with the results of previous studies. TOC contents in high As boreholes ranged from0.002to1.854wt.%, and positively correlated with total As. Most of the high As sediments were clay or silty clay samples, characterized with high concentrations of total sulfur, iron and high TOC contents.
2. Spatial distribution of microbial communities in high As aquifers of Hetao Plain, Inner Mongolia.
Based on the geochemistry results, several groundwater and sediment samples were selected for the analysis of structure and diversity of microbial communities using PCR-DGGE,16S rRNA gene clone library and Illumina MiSeq sequencing approaches.
DGGE analysis results indicated that community structures in high As sediments were complex and distinctly different from low As sediment samples. In high As sediment samples, DGGE bands related with Pseudomonas and Acinebacter faded out as the total As concentrations decrease and Thiobacillus appeared as concentrations of sulfate increase. The phylogenetic relationship and closest relatives in GenBank divided these bands sequences from high As boreholes into four groups:Alpha-, Beta-, Gamma-proteobacteria and Firmicutes. Some bands were identified as genus Pseudomonas, Brevundimonas, and Sporosarcina which were highly similar with microorganisms capable of As resistance. Some other bands showed high similarity to Pseudomonas and Thiobacillus. As reported by previous studies, these two species were closely related with bacteria with sulfur-oxidizing or denitrification in freshwater and soil system. The dominant populations in the control borehole were mostly similar with bacteria found in cold arctic marine sediment or permafrost wetland. Populations within sediment samples from control borehole presented higher diversity than in high As sediments, which was consistent with the results reported in Bangladesh aquifers. The result of16S rRNA gene clone libraries in high As sediment samples showed that most of bacteria in Hetao Plain were affiliated with the Betaproteobacteria, which was similar with that of previous studies on high As streambed sediments. Among all the bacterial populations, more than70%clones were closed related (100%similarity) with a thiosulfate-oxidizing bacterium Thiobacillus thioparus. Besides, Pseudomonas, Brevundimonas and Hydrogenophaga were also the dominant populations in high As sediments. In our previous study, a large amount of As containing pyrite (FeS2) was found in the sampling site. The release of As, sulfate and Fe might be related to the oxidation of As-containing pyrite by the microbial populations such as Thiobacillus, and this would result in the accumulation of As(Ⅴ) onto surfaces of the oxidized minerals. The absorbed arsenate was reduced into arsenite which was more mobile because of its poor affinity for mineral surfaces. This might be the reason for the dominance of As(Ⅴ) in high sediment samples as well as for that of As(Ⅲ) in high As groundwater.
The results of16S rRNA gene clone library of three representative groundwater samples indicated that bacteria in high As groundwater could be grouped into twelve bacterial classes: Alpha-, Beta-Delta-, Epsilon-, and Gammaproteobacteria, Chlorobi, Bacteroidetes, Firmicutes, Chloroflexi, Actinobacteria, and Deinococcus-Thermus. The sample with the highest As(Ⅲ)/total As ratio showed the highest bacterial diversity and was mainly dominated by Alphaproteobacteria and Betaproteobacteria, which was different from other two samples that dominated by Gammaproteobacteria. But at the genus level, all of these three samples were dominated by Acinetobacter and Pseudomonas with different relative abundances. Generally speaking, dominant populations in high As groundwater included Acinetobacter, Pseudomonas, Brevundimonas, Geobacter and Aquabacterium. Similarly, the archaeal16S rRNA gene clone library result showed that archaeal populations in the sample with the lowest As concentration was more diverse than the other two samples, suggesting that As toxicity can decrease archaeal diversity. Archaea populations in high As groundwater fell into Thaumarchaeota, Crenarchaeota and Euryarchaeota. Among them, Thaumarchaeota was a newly established phylum containing all known ammonia-oxidizing archaea. DGGE result showed that the number of Thaumarchaeota-related sequences decreased gradually as nitrate concentrations decreased and As concentrations increased. Dominant archaeal populations in high As groundwater included Methanosaeta (belong to Euryarchaeota), Nitrosophaera (belong to Thaumarchaeota) and Thermoprotei (belong to Crenarchaeota). These results suggested that microbe-mediated ammonia oxidation and sulfur reduction might be involved in arsenic mobilization in groundwater systems.
Illumina MiSeq sequencing results revealed that groundwater samples with different geochemical characteristics presented significantly different microbial community structures. Most groundwater samples were dominated by populations including Acinetobacter, Rheinheimera, Pseudomonas, Methylotenera, Aquabacterium, Hydrogenophaga, Crenothrix and LCP-6, which was mostly consistent with the result of16S rDNA clone libraries. However, Rheinheimera, Methylotenera, Crenothrix and LCP-6were not found in the clone library analysis, which might imply the possible bias between these two methods. The top ten OTUs for dissimilarity between high As groundwaters and low As groundwaters included Acinetobacter, Pseudomonas, Psedudomonadaceae, Alishewanella, Psychrobacter which were more abundant in high As groundwater, and Rheinheimera, Aquabacterium, Comamonadaceae and Gallionella which dominated in low As groundwater.
Statistical analysis showed that samples with different As concentrations presented distinctly different values of other geochemical parameters. Besides, microbial communities were different in high As groundwater as compared to low As samples, and some other environmental variables had also effects with microbial communities.
Evaluating the results of microbial communities in both high As sediment and groundwater in the same location, it can be concluded that the microbial community structure in high As sediments was totally different from that of high As groundwater. The distribution difference of As(III) and As(V) as well as the microbial populations between high As sediments and groundwater implied that the microbially mediated mechanism of As mobilization was potential different in sediments and groundwater.
3. Functional microbial communities in strongly reducing As groundwater
Analysis of the diversity and abundance of functional populations in groundwater were essential for understanding the microbial ecology and biogeochemical processes in aquifer systems. Hydrogeochemical parameters indicated that the high As groundwater in Hetao Plain was under strongly reducing conditions, along with high concentrations of As, TOC and CH4and low concentrations of sulfate. Therefore, community structure and abundance of sulfate-reducing bacteria, methanogenic archaea, As-oxidizing and reducing bacteria in high As groundwater of Hetao Plain were investigated using corresponding functional genes. Analysis of aioA gene clone library indicated that As-oxidizing bacteria in high As groundwater of Hetao Plain were all belonged to Proteobacteria including Betaproteobacteria, Gammaproteobacteria and Alphaproteobacteria. All clones in Betaproteobacteria belonged to Burkholderiales which contained Rhodoferax ferrireducens, Leptothrix sp., and Acidovorax sp.. Previously studies showed that Rhodoferax ferrireducens was one kind of anaerobic bacterium that could grow from dissimilatory Fe(III) reduction, and Leptothnix sp. and Acidovorax sp. were isolated from As-contaminated sediment and As-contaminated mining site. Clones in Gammaproteobacteria showed high similarity with species of Pseudomonas and Acinetobacter, which was consistent with the abundant existence of Pseudomonas and Acinetobacter when investigating the distribution of microbial communities in high As groundwater. Clones affiliated with Alphaproteobacteria were closely related to the order Rhizobiales, such as Xanthobacter autotrophicus, Bradyrhizobium sp., Bosea sp., Aminobacter sp. and Nitrobacter hamburgensis, which were previously found in As-contaminated soil or As-mining sites. As-oxidizing bacteria in high As groundwater in Hetao Plain were dominated by Rhodoferax ferrireducens, Leptothrix sp., Acidovorax sp., Pseudomonas sp. and Acinetobacter sp.. As-reducing populations in high As groundwater mainly occurred in Deltaproteobacteria, Betaproteobacteria, Chrysiogenetes, Firmicutes and an uncultured group, among which the uncultured group accounted for about one-third. Dominant populations included Geobacter sp., Desulfosporosinus sp., Chrysiogenes and Desulfurispirillum. Most of these populations were found capable of dissimilatory arsenate reducing or sulfur oxidizing in previously studies. The uncultured group was highly similar with uncultured dissimilatory arsenate reducing bacteria in high As sediment and groundwater of West Bengal and north Utah. The concurrence of As-oxidizing bacteria and As-reducing bacteria in high As groundwater implied the complexity of microbially mediated As mobilization in high As aquifers.
The analysis of methanogenic archaea in18high As groundwaters showed that the abundance of mcrA gene ranged from3.01×103copies/L to3.80×106copies/L and presented higher abundance in samples with high CH4concentrations. The relative abundance of mcrA gene to total archaea was0.0-30.2%, and presented positive correlations with total As and Fe(II). This could imply that methanogens were more abundant in samples with high As concentrations and were related to dissolution of As-containing minerals. Besides, the relative abundance of mcrA gene to total archaea was negative exponentially related to the sulfate concentrations, which showed consistency with previous results that the consumption of sulfate in high As groundwater could accelerate CH4accumulation. Clone library result of mcrA gene indicated methanogens in high As groundwater were mainly composed of Methanomicrobia, Methanobacteria and the uncultured group, among which83%clones belonged to Methanomicrobia including Methanomicrobiales and Methanosarcinales. Previous studies showed that most of these methanogenic archaea were from peat bog, permafrost and metal-contaminated sediments. Besides, some clones in this study showed extremely low similarity with previously identified mcrA gene sequences, implying the possible presence of special methanogenic populations in high As groundwater.
The abundance of bacterial16S gene and dsrB gene in high As groundwater were8.74×106-4.12×109copies/L and0-4.9×106copies/L respectively. The highest percentage of dsrB gene copies to bacterial16S rRNA gene copies was2.1%. The abundance of dsrB gene was positive exponentially correlated with As concentrations, which could imply sulfate reduction occurs simultaneously with As and Fe reduction, and might result in increased As release and mobilization when As is not incorporated into iron sulfides. DGGE result showed that sulfate reducing bacteria in high As groundwater belonged to either Firmicutes or Deltaproteobacteria, and were mainly dominated by Desulfotomaculum, Desulfobulbus, Desulfosarcina and Desulfobacca. Desulfotomaculum was previously found in As contaminated environment capable of metabolizing using As as electron acceptor.
本研究以我国原生高砷地下水典型地区内蒙古河套平原杭锦后旗为研究区,将地球化学分析与先进的微生物分子生态学手段和方法相结合,通过研究高砷地下水和沉积物中的微生物多样性及其群落结构特征,分析强还原高砷地下水中的功能微生物群落,并与地球化学参数相结合,探讨微生物群落在高砷地下水迁移富集过程中的作用机理。研究的主要成果如下：
1.河套平原杭锦后旗典型强还原条件下高砷地下水和沉积物的地球化学特征。
以杭锦后旗作为典型研究区,通过大量野外调查和前期研究总结,有针对性的采集了典型高砷地下水样品21件和3个钻孔(包括2个高砷钻孔和1个低砷钻孔)的垂向沉积物样品32件,分析了高砷地下水样品中水化学环境与砷浓度之间的关系,刻画了沉积物样品中砷(形态)、铁、硫、TOC等的垂向分布特征。研究区多数高砷地下水的氧化还原电位为负值,pH为近中性或弱碱性。样品总砷和三价砷的浓度范围分别为65.6-1088.7μg/L和14.5-560.3μg/L,其中超过半数样品的三价砷浓度高于五价砷浓度。三价砷浓度和总砷浓度之间呈现出良好的线性相关关系。总铁浓度变化为107-2257μg/L。甲烷浓度随着总砷浓度的增加而升高,最高值可达568.20μg/L。所有样品的硝酸盐含量都非常低,而硫酸盐含量只在总砷含量非常低时显著增高。样品中的TOC浓度为1.9-11.9mg/L。TOC含量以及Fe(Ⅱ)/Fe(Ⅲ)均与总砷浓度呈现出正相关关系,而硫酸根含量则与总砷浓度呈指数负相关。多数高砷地下水样品具有高浓度的三价砷、TOC、Fe(Ⅱ)/Fe(Ⅲ)和低浓度的硫酸根、硝酸根。
高砷沉积物样品中砷含量为33.6-77.6mg/kg,而对照低砷沉积物样品的砷含量仅为1.5-5.8mg/kg。所有样品中均没有检测到一甲基砷和二甲基砷。在高砷沉积物钻孔中,三价砷的含量随深度而增加,但是所有样品均以五价砷为主。高砷沉积物中亚铁和三价铁的含量分别为0.05-7.01g/kg和0.38-5.29g/kg,亚铁和总铁的比值随着深度的增加而增大。总铁与总砷呈现出相同的变化趋势,与已有的研究结果一致。TOC含量为0.002-1.854wt.%,与总砷含量呈正相关关系。高砷沉积物主要出现在粘土和亚粘土样品中,这些样品同时表现出高浓度的硫、铁和TOC含量。
2.浅层强还原高砷地下水系统中的微生物群落多样性和群落结构的空间变化规律。
在以上研究结果的基础上,选取典型强还原区高砷地下水和沉积物样品,采用PCR-DGGE指纹图谱和16S rRNA基因克隆文库、Illumina Miseq测序等微生物分子生态学研究方法,并结合样品中砷、铁、硫等的分布特征,研究高砷地下水系统中的原位微生物群落在地下水和沉积物中的空间分布特征及多样性。
沉积物样品的PCR-DGGE指纹图谱分析结果表明,高砷沉积物中微生物群落结构与低砷沉积物显著不同。在图谱中,与假单胞菌属和不动杆菌属有关的条带随着总砷浓度的降低而逐渐淡出,而与硫杆菌属相关的条带随着硫酸根浓度的增加而增强。对高砷沉积物钻孔样品中微生物群落的系统发育关系进行构建,高砷沉积物中主要包括四类微生物：α-,β-,γ-变形菌和厚壁菌门。其中一些DGGE条带序列与假单胞菌、短波单胞菌和八叠球菌等菌有关,已有研究证明这些细菌种群具有很强的砷抗性。另一些条带序列与假单胞菌和硫杆菌十分相似,这两种细菌与淡水或土壤系统中的硫氧化和反硝化作用紧密相关。低砷沉积物样品中的优势种群主要与寒冷环境如海洋沉积物和永冻土中的微生物相似。研究发现,低砷沉积物样品的微生物群落多样性高于高砷沉积物样品,这与对孟加拉国含水层的研究结果一致。高砷沉积物样品的16S rRNA基因克隆文库研究结果发现,河套平原高砷沉积物中以β-变形菌为主,这与之前对高砷河床沉积物开展的研究结果相似。其中,超过70%的克隆子与具有硫氧化和铁氧化功能的硫杆菌高度相似。此外,假单胞菌、短波单胞菌和嗜氢菌属也是高砷沉积物中的优势种群。本研究组在已有的研究中发现在采样点有大量含砷黄铁矿的存在,推测在微生物群落如硫杆菌的作用下,含砷黄铁矿的氧化可能导致砷、硫和铁的释放,五价砷酸盐在氧化性矿物表面富集。此后,被吸附的五价砷被还原为在矿物表面吸附性较差的三价砷进入地下水系统。这可能是沉积物中以As(V)为主而地下水中则以As(Ⅲ)为主的原因。
三个典型水样的16S rRNA基因克隆文库的研究结果表明：高砷地下水样品中的细菌群落分为12类,包括α-、β-、δ-、ε-和γ-变形菌门、绿细菌门、拟杆菌门、厚壁菌门、绿弯菌门、放线菌门以及异常球菌-栖热菌门。其中三价砷占总砷比例最大的样品呈现出最高的群落多样性。此外,在纲的分类水平上,该样品以α-变形菌纲和β-变形菌纲为主,不同于砷含量最低和砷含量最高的两个样品。但是在属的分类水平上,三个样品的优势种群均属于不动杆菌属和假单胞菌属。总体来说,高砷地下水中的优势细菌群落包括不动杆菌属,假单胞菌属,短波单胞菌属,嗜酸菌属和水杆菌属。同样地,对高砷地下水中古菌群落的分析结果显示,砷含量最低的样品古菌群落多样性最高,说明砷的毒性可能降低高砷地下水中古菌的多样性。高砷地下水中古菌群落包括奇古菌门、泉古菌门和广古菌门。其中,奇古菌门是一类新分类的古菌,包括所有已知的氨氧化古菌。研究中与奇古菌门相关的条带亮度随着样品硝酸根浓度的降低和砷浓度的增加而逐渐减弱。文库分析结果显示高砷地下水中古菌的优势群落为甲烷丝状菌(属于广古菌门),Nitrosophaera(属于奇古菌门)和热变形菌(属于泉古菌门)。热变形菌可以利用H2作为电子供体进行硫还原。这些结果揭示出高砷地下水中微生物作用下的氨氧化和硫氧化反应的存在。
高砷地下水Illumina MiSeq测序结果表明水化参数不同的样品的微生物群落也显著不同。多数地下水中的优势种群包括不动杆菌、Rheinheimera、假单胞菌、Methylotenera、水杆菌、噬氢菌、泉发菌和LCP-6等,与文库分析结果基本一致。但在文库分析时未发现Rheinheimera,Methyloteenera,泉发菌和LCP-6,表明文库分析和高通量测序之间可能存在一定的偏差。研究发现,造成高砷地下水和低砷地下水差异性的前十位微生物种群包括不动杆菌、假单胞菌、Alishewanella、嗜冷菌、Rheinheimera、水杆菌、丛毛单胞菌和披毛菌。统计学分析结果表明,砷含量不同的地下水样品,其他的水化参数也显著不同。此外,高砷地下水与低砷地下水中的微生物优势群落显著不同,除了砷浓度主要影响外,其他环境因子也可能导致群落构成的不同。
通过对同一采样点的沉积物和地下水样品的微生物群落对比发现,高砷沉积物中的微生物群落与高砷地下水中的微生物群落显著不同。沉积物和地下水中砷形态的不同分配,以及不同的微生物群落构成,都表明微生物作用下的沉积物和地下水中砷的迁移转化机制可能不同。
3.强还原高砷地下水中的功能微生物群落
研究高砷地下水环境中功能群落的多样性和丰度,能更好地理解微生物生态和与高砷环境相关的微生物作用。前面的研究结果表明,河套平原高砷地下水处于强还原条件下,并伴有高浓度的砷、TOC和甲烷以及低浓度的硫酸盐和硝酸盐。因此,本论文通过对微生物功能基因的研究,对河套平原高砷地下水中的硫酸盐还原菌、产甲烷菌、砷氧化菌和砷还原菌的群落结构特征与丰富度进行了分析。
通过对细菌砷氧化基因aioA的基因文库分析,发现河套地区高砷地下水中的砷氧化菌均属于变形菌门,包括α-、β和γ-变形菌。其中,β-变形菌纲的克隆子均属于伯克氏菌目,与Rhodoferax ferrireducens、纤毛菌属和嗜酸菌属的细菌高度相似。Rhodoferax ferrireducens是一类可以进行异化铁还原的厌氧菌。纤毛菌属和嗜酸菌属的细菌曾从砷污染的沉积物或者含砷尾矿点分离得到。属于γ-变形菌纲的克隆与假单胞菌属和不动杆菌属的细菌相似,这与高砷地下水中的微生物群落中大量存在假单胞菌和不动杆菌的结果一致。属于α-变形菌纲的克隆与根瘤菌目的细菌,包括自养黄杆菌、慢生根瘤菌、氨基杆菌、Bosea sp和汉氏硝化菌等相似。前人研究表明这些种属的细菌大部分来自从砷污染的土壤。河套高砷地下水中砷氧化菌优势群落包括Rhodoferax ferrireducens、纤毛菌、嗜酸菌、假单胞菌和不动杆菌。高砷地下水中的砷还原群落主要分布在δ-变形菌、β-变形菌、产金菌门和厚壁菌门以及不可培养未鉴定的群落,其中不可培养未鉴定的种群占到约三分之一。优势群落包括地杆菌、脱硫芽孢弯菌、产金菌和Desulfurispirillum,这些菌落多是能进行异化砷酸盐还原或者硫氧化的细菌。而未培养的群落与在西孟加拉和美国北犹他州高砷沉积物或地下水中发现的不可培养异化砷还原菌相似度较高。河套平原高砷地下水中砷还原菌和砷氧化菌的同时存在,也说明了地下水系统中与微生物作用有关的砷迁移转化的复杂性。
对18个高砷地下水样品中的产甲烷菌进行分析,结果表明mcrA基因的丰度为3.01×103到3.80×106拷贝/L,在甲烷含量高的样品中丰度更大。mcrA基因占总古菌的比例(相对丰度)为0.0-30.2%。研究发现,mcrA基因的相对丰度与样品的总砷以及亚铁含量呈正相关,这可能预示产甲烷菌在砷含量高的样品中更加丰富,并且与含砷矿物的溶解有关。此外,mcrA基因的相对丰度与样品的硫酸盐含量呈明显的负指数相关,这与已有研究结果中提出的高砷地下水中硫酸盐的消耗可以加速甲烷的积累一致。克隆文库结果显示,高砷地下水中的甲烷菌包括甲烷微菌纲、甲烷杆菌纲和不可培养群落,其中83%克隆子属于甲烷微菌纲,包括甲烷微菌目和甲烷八叠球菌目。这些种属的产甲烷菌多分离自泥炭沼泽、消化淤泥、永冻土和金属污染的沉积物。此外,研究中发现一些克隆序列与已知的mcrA基因序列相似度极低,表明高砷地下水中可能有新的产甲烷类群的存在。
对21个高砷地下水中的硫酸盐还原菌功能基因dsrB进行分析,发现高砷地下水中细菌16S基因和dsrB基因的丰度分别为8.74×106-4.12×109拷贝/L和0-4.9×106拷贝几。其中有7个样品的dsrB相对丰度超过0.1%,最高为2.1%。dsrB基因丰度与地下水样品的总砷浓度呈正指数相关关系,可以推测硫酸盐还原与砷和铁的还原可能同时发生。DGGE指纹图谱分析结果显示,高砷地下水中的硫酸盐还原菌属于厚壁菌门和δ-变形菌,优势群落包括脱硫肠状菌、脱硫叶菌、脱硫叠球菌和Desulfobacca。之前已有研究在砷污染环境中发现脱硫肠状菌能够将砷作为电子受体进行代谢。
High arsenic (As) groundwater has become one of the most serious environmental problems nowadays, threatening the lives of more than140million people. At present, high As groundwater has been found in more than17Countries including Bangladesh, India, Vietnam, Argentina, Chile, Japan, USA and China. In China, high As groundwater are mainly distributed in Xinjiang, Shanxi, Inner Mongolia, Taiwan and Guizhou, with more than3million people under threat. Long term intake of high As groundwater can cause many chronic diseases and severe cancers such as vascular disease, skin cancer, respiration and heart cancer. Nowadays, many studies have been conducted concerning geogenic As groundwater and focused on hydrogeochemistry, mineralogy and deposit conditions. Previous studies indicated that As release and mobilization in aquifers are integrated results of series of microbially mediated reactions and geochemical processes. Microorganisms as one kind of important geological mediators, their resistance, and oxidizing or reducing capacity can allow them to function and affect mobilization of absorbed As. At present, three mechanisms of As enrichment in groundwater systems have been proposed in microbes can play important roles:oxidation of As-rich sulfide mineral, reductive dissolution of Fe(III) oxyhydroxides, and dissimilatory reduction of As. Therefore, to better understand the microbially mediated mechanism of As mobilization and release, it is worthy of studying the in situ microbial community structures and diversities and the functional microbial populations in high As aquifers.
In this study, microbially mediated As release and mobilization in strongly reducing aquifers of Hetao Plain were studied using both geochemical and microbial molecular methods, to analyze the geochemistry of groundwater and aquifer sediments, to investigate microbial community structure and diversity in sediments and groundwater with different geochemical characteristics, and to explore functional microbial communities in strongly reducing As groundwater. The main results are as follows:
1. Geochemical characteristics of high As groundwaters and sediments in Hetao Plain.
Twenty-one high As groundwater samples and thirty-two sediment samples from three boreholes which included two high As borehole and one control borehole were collected for geochemical analysis including As speciation, Fe, S and TOC. Most groundwater samples had negative Eh values under near neutral or weakly alkaline conditions. Concentrations of total As and As(Ⅲ) varied in the range of65.6-1088.7μg/L and14.5-560.3μg/L, respectively. As(Ⅲ) concentrations in more than half of the samples were higher than As(V) and concentrations of As(Ⅲ) and total As showed positive linear relationship. Total iron concentrations changed between107μg/L and2257μg/L. Methane concentrations increased with total As concentrations, with the highest value of568.20μg/L. Sulfate concentrations were relatively low in all samples while distinctly elevated only when total As concentrations were low. TOC concentrations ranged from1.9mg/L to11.9mg/L. TOC concentrations and Fe(Ⅱ)/Fe(Ⅲ) values showed positive correlation with total As concentrations, while sulfate concentrations presented negative exponential correlation with total As. Most of high As groundwaters were characterized with high concentrations of As(Ⅲ), TOC, Fe(Ⅱ)/Fe(Ⅲ) and low concentrations of sulfate and nitrate.
Arsenic contents in high As sediments varied between33.6mg/kg and77.6mg/kg while in low As sediments ranged from1.5mg/kg to5.8mg/kg. MMAV and DMAV were under the detection limits in all sediment samples. In high As boreholes, As(Ⅲ) contents increased with depth, but As(Ⅴ) dominated in all samples. The concentrations of Fe(Ⅱ) and Fe(Ⅲ) in the high As sediments lay in the range0.05-7.01g/kg and0.38-5.29g/kg, the ratios of Fe(Ⅱ) to total Fe increased with depth. Positive correlation was found between total Fe and total As, which was consistent with the results of previous studies. TOC contents in high As boreholes ranged from0.002to1.854wt.%, and positively correlated with total As. Most of the high As sediments were clay or silty clay samples, characterized with high concentrations of total sulfur, iron and high TOC contents.
2. Spatial distribution of microbial communities in high As aquifers of Hetao Plain, Inner Mongolia.
Based on the geochemistry results, several groundwater and sediment samples were selected for the analysis of structure and diversity of microbial communities using PCR-DGGE,16S rRNA gene clone library and Illumina MiSeq sequencing approaches.
DGGE analysis results indicated that community structures in high As sediments were complex and distinctly different from low As sediment samples. In high As sediment samples, DGGE bands related with Pseudomonas and Acinebacter faded out as the total As concentrations decrease and Thiobacillus appeared as concentrations of sulfate increase. The phylogenetic relationship and closest relatives in GenBank divided these bands sequences from high As boreholes into four groups:Alpha-, Beta-, Gamma-proteobacteria and Firmicutes. Some bands were identified as genus Pseudomonas, Brevundimonas, and Sporosarcina which were highly similar with microorganisms capable of As resistance. Some other bands showed high similarity to Pseudomonas and Thiobacillus. As reported by previous studies, these two species were closely related with bacteria with sulfur-oxidizing or denitrification in freshwater and soil system. The dominant populations in the control borehole were mostly similar with bacteria found in cold arctic marine sediment or permafrost wetland. Populations within sediment samples from control borehole presented higher diversity than in high As sediments, which was consistent with the results reported in Bangladesh aquifers. The result of16S rRNA gene clone libraries in high As sediment samples showed that most of bacteria in Hetao Plain were affiliated with the Betaproteobacteria, which was similar with that of previous studies on high As streambed sediments. Among all the bacterial populations, more than70%clones were closed related (100%similarity) with a thiosulfate-oxidizing bacterium Thiobacillus thioparus. Besides, Pseudomonas, Brevundimonas and Hydrogenophaga were also the dominant populations in high As sediments. In our previous study, a large amount of As containing pyrite (FeS2) was found in the sampling site. The release of As, sulfate and Fe might be related to the oxidation of As-containing pyrite by the microbial populations such as Thiobacillus, and this would result in the accumulation of As(Ⅴ) onto surfaces of the oxidized minerals. The absorbed arsenate was reduced into arsenite which was more mobile because of its poor affinity for mineral surfaces. This might be the reason for the dominance of As(Ⅴ) in high sediment samples as well as for that of As(Ⅲ) in high As groundwater.
The results of16S rRNA gene clone library of three representative groundwater samples indicated that bacteria in high As groundwater could be grouped into twelve bacterial classes: Alpha-, Beta-Delta-, Epsilon-, and Gammaproteobacteria, Chlorobi, Bacteroidetes, Firmicutes, Chloroflexi, Actinobacteria, and Deinococcus-Thermus. The sample with the highest As(Ⅲ)/total As ratio showed the highest bacterial diversity and was mainly dominated by Alphaproteobacteria and Betaproteobacteria, which was different from other two samples that dominated by Gammaproteobacteria. But at the genus level, all of these three samples were dominated by Acinetobacter and Pseudomonas with different relative abundances. Generally speaking, dominant populations in high As groundwater included Acinetobacter, Pseudomonas, Brevundimonas, Geobacter and Aquabacterium. Similarly, the archaeal16S rRNA gene clone library result showed that archaeal populations in the sample with the lowest As concentration was more diverse than the other two samples, suggesting that As toxicity can decrease archaeal diversity. Archaea populations in high As groundwater fell into Thaumarchaeota, Crenarchaeota and Euryarchaeota. Among them, Thaumarchaeota was a newly established phylum containing all known ammonia-oxidizing archaea. DGGE result showed that the number of Thaumarchaeota-related sequences decreased gradually as nitrate concentrations decreased and As concentrations increased. Dominant archaeal populations in high As groundwater included Methanosaeta (belong to Euryarchaeota), Nitrosophaera (belong to Thaumarchaeota) and Thermoprotei (belong to Crenarchaeota). These results suggested that microbe-mediated ammonia oxidation and sulfur reduction might be involved in arsenic mobilization in groundwater systems.
Illumina MiSeq sequencing results revealed that groundwater samples with different geochemical characteristics presented significantly different microbial community structures. Most groundwater samples were dominated by populations including Acinetobacter, Rheinheimera, Pseudomonas, Methylotenera, Aquabacterium, Hydrogenophaga, Crenothrix and LCP-6, which was mostly consistent with the result of16S rDNA clone libraries. However, Rheinheimera, Methylotenera, Crenothrix and LCP-6were not found in the clone library analysis, which might imply the possible bias between these two methods. The top ten OTUs for dissimilarity between high As groundwaters and low As groundwaters included Acinetobacter, Pseudomonas, Psedudomonadaceae, Alishewanella, Psychrobacter which were more abundant in high As groundwater, and Rheinheimera, Aquabacterium, Comamonadaceae and Gallionella which dominated in low As groundwater.
Statistical analysis showed that samples with different As concentrations presented distinctly different values of other geochemical parameters. Besides, microbial communities were different in high As groundwater as compared to low As samples, and some other environmental variables had also effects with microbial communities.
Evaluating the results of microbial communities in both high As sediment and groundwater in the same location, it can be concluded that the microbial community structure in high As sediments was totally different from that of high As groundwater. The distribution difference of As(III) and As(V) as well as the microbial populations between high As sediments and groundwater implied that the microbially mediated mechanism of As mobilization was potential different in sediments and groundwater.
3. Functional microbial communities in strongly reducing As groundwater
Analysis of the diversity and abundance of functional populations in groundwater were essential for understanding the microbial ecology and biogeochemical processes in aquifer systems. Hydrogeochemical parameters indicated that the high As groundwater in Hetao Plain was under strongly reducing conditions, along with high concentrations of As, TOC and CH4and low concentrations of sulfate. Therefore, community structure and abundance of sulfate-reducing bacteria, methanogenic archaea, As-oxidizing and reducing bacteria in high As groundwater of Hetao Plain were investigated using corresponding functional genes. Analysis of aioA gene clone library indicated that As-oxidizing bacteria in high As groundwater of Hetao Plain were all belonged to Proteobacteria including Betaproteobacteria, Gammaproteobacteria and Alphaproteobacteria. All clones in Betaproteobacteria belonged to Burkholderiales which contained Rhodoferax ferrireducens, Leptothrix sp., and Acidovorax sp.. Previously studies showed that Rhodoferax ferrireducens was one kind of anaerobic bacterium that could grow from dissimilatory Fe(III) reduction, and Leptothnix sp. and Acidovorax sp. were isolated from As-contaminated sediment and As-contaminated mining site. Clones in Gammaproteobacteria showed high similarity with species of Pseudomonas and Acinetobacter, which was consistent with the abundant existence of Pseudomonas and Acinetobacter when investigating the distribution of microbial communities in high As groundwater. Clones affiliated with Alphaproteobacteria were closely related to the order Rhizobiales, such as Xanthobacter autotrophicus, Bradyrhizobium sp., Bosea sp., Aminobacter sp. and Nitrobacter hamburgensis, which were previously found in As-contaminated soil or As-mining sites. As-oxidizing bacteria in high As groundwater in Hetao Plain were dominated by Rhodoferax ferrireducens, Leptothrix sp., Acidovorax sp., Pseudomonas sp. and Acinetobacter sp.. As-reducing populations in high As groundwater mainly occurred in Deltaproteobacteria, Betaproteobacteria, Chrysiogenetes, Firmicutes and an uncultured group, among which the uncultured group accounted for about one-third. Dominant populations included Geobacter sp., Desulfosporosinus sp., Chrysiogenes and Desulfurispirillum. Most of these populations were found capable of dissimilatory arsenate reducing or sulfur oxidizing in previously studies. The uncultured group was highly similar with uncultured dissimilatory arsenate reducing bacteria in high As sediment and groundwater of West Bengal and north Utah. The concurrence of As-oxidizing bacteria and As-reducing bacteria in high As groundwater implied the complexity of microbially mediated As mobilization in high As aquifers.
The analysis of methanogenic archaea in18high As groundwaters showed that the abundance of mcrA gene ranged from3.01×103copies/L to3.80×106copies/L and presented higher abundance in samples with high CH4concentrations. The relative abundance of mcrA gene to total archaea was0.0-30.2%, and presented positive correlations with total As and Fe(II). This could imply that methanogens were more abundant in samples with high As concentrations and were related to dissolution of As-containing minerals. Besides, the relative abundance of mcrA gene to total archaea was negative exponentially related to the sulfate concentrations, which showed consistency with previous results that the consumption of sulfate in high As groundwater could accelerate CH4accumulation. Clone library result of mcrA gene indicated methanogens in high As groundwater were mainly composed of Methanomicrobia, Methanobacteria and the uncultured group, among which83%clones belonged to Methanomicrobia including Methanomicrobiales and Methanosarcinales. Previous studies showed that most of these methanogenic archaea were from peat bog, permafrost and metal-contaminated sediments. Besides, some clones in this study showed extremely low similarity with previously identified mcrA gene sequences, implying the possible presence of special methanogenic populations in high As groundwater.
The abundance of bacterial16S gene and dsrB gene in high As groundwater were8.74×106-4.12×109copies/L and0-4.9×106copies/L respectively. The highest percentage of dsrB gene copies to bacterial16S rRNA gene copies was2.1%. The abundance of dsrB gene was positive exponentially correlated with As concentrations, which could imply sulfate reduction occurs simultaneously with As and Fe reduction, and might result in increased As release and mobilization when As is not incorporated into iron sulfides. DGGE result showed that sulfate reducing bacteria in high As groundwater belonged to either Firmicutes or Deltaproteobacteria, and were mainly dominated by Desulfotomaculum, Desulfobulbus, Desulfosarcina and Desulfobacca. Desulfotomaculum was previously found in As contaminated environment capable of metabolizing using As as electron acceptor.
引文
[1]Ravenscroft P, Brammer H and Richards K. Arsenic pollution:a global synthesis. Vol.94 (Wiley.com,2011).
[2]Fan H, Su C, Wang Y, et al. Sedimentary arsenite-oxidizing and arsenate-reducing bacteria associated with high arsenic groundwater from Shanyin, Northwestern China. J. Appl. Microbiol. (2008) 105:529-539
[3]Barringer JL, Reilly PA, Eberl DD, et al. Arsenic in sediments, groundwater, and streamwater of a glauconitic Coastal Plain terrain, New Jersey, USA-Chemical "fingerprints" for geogenic and anthropogenic sources. Appl. Geochem. (2011) 26: 763-776
[4]Bhattacharya P, Claesson M, Fagerberg J, et al. Natural arsenic in the groundwater of the alluvial aquifers of Santiago del Estero Province, Argentina. (2005):57-65
[5]Harvey CF, Swartz CH, Badruzzaman ABM, et al. Arsenic mobility and groundwater extraction in Bangladesh. Science (2002) 298:1602-1606
[6]Meharg AA, Scrimgeour C, Hossain SA, et al. Codeposition of organic carbon and arsenic in Bengal Delta aquifers. Environ. Sci. Technol. (2006) 40:4928-4935
[7]Winkel LH, Trang PTK, Lan VM, et al. Arsenic pollution of groundwater in Vietnam exacerbated by deep aquifer exploitation for more than a century. Proc. Nat. Aca. Sci. (2011)108:1246-1251
[8]Liu J, Zheng B, Aposhian HV, et al. Chronic arsenic poisoning from burning high-arsenic-containing coal in Guizhou, China. J. Peripher. Nerv. Syst. (2002) 7: 208-208
[9]Guo XJ, Fujino Y, Kaneko S, et al. Arsenic contamination of groundwater and prevalence of arsenical dermatosis in the Hetao plain area, Inner Mongolia, China. Mol. Cell. Biochem. (2001) 222:137-140
[10]Luo T, Hu S, Cui J, et al. Comparison of Arsenic geochemical evolution in the Datong Basin (Shanxi) and Hetao Basin (Inner Mongolia), China. Appl. Geochem. (2012) 27: 2315-2323
[11]Tseng C-H, Chong C-K, Tseng C-P, et al. Long-term arsenic exposure and ischemic heart disease in arseniasis-hyperendemic villages in Taiwan. Toxicol. Lett. (2003) 137:15-21
[12]Michael HA. An arsenic forecast for China. Science (2013) 341:852-853
[13]Ferreccio C, Sancha AM. Arsenic exposure and its impact on health in Chile. J. Health. Popul. Nutr. (2011) 24:164-175
[14]Jomova K, Jenisova Z, Feszterova M, et al. Arsenic:toxicity, oxidative stress and human disease. J. Appl. Toxicol. (2011) 31:95-107
[15]Knobeloch LM, Zierold KM and Anderson HA. Association of arsenic-contaminated drinking-water with prevalence of skin cancer in Wisconsin's Fox River Valley. J. Health. Popul. Nutr. (2011) 24:206-213
[16]胡立刚,蔡勇.砷的生物地球化学.化学进展(2009)：458-466
[17]Erban LE, Gorelick SM, Zebker HA, et al. Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence. Proc. Nat. Aca. Sci. (2013).
[18]Majumder S, Sarkar S, Chatterjee D, et al. Role of colloidal particles as scavengers of groundwater arsenic:A case study from rural Bengal. Procedia Earth Planetary Sci. (2013)7:546-549
[19]Radloff K, Zheng Y, Michael H, et al. Arsenic migration to deep groundwater in Bangladesh influenced by adsorption and water demand. Nat. Geosci. (2011) 4:793-798
[20]Routh J, Hjelmquist P. Distribution of arsenic and its mobility in shallow aquifer sediments from Ambikanagar, West Bengal, India. Appl. Geochem. (2011) 26:505-515
[21]Anawar HM, Akai J, Mihaljevic M, et al. Arsenic contamination in groundwater of Bangladesh:Perspectives on geochemical, microbial and anthropogenic Issues. Water (2011)3:1050-1076
[22]Nickson RT, McArthur JM, Ravenscroft P, et al. Mechanism of arsenic release to groundwater, Bangladesh and West Bengal. Appl. Geochem. (2000) 15:403-413
[23]Ahmed KM, Bhattacharya P, Hasan MA, et al. Arsenic enrichment in groundwater of the alluvial aquifers in Bangladesh:an overview. Appl. Geochem. (2004) 19:181-200
[24]Kulp TR, Hoeft SE, Asao M, et al. Arsenic(III) fuels anoxygenic photosynthesis in hot spring biofilms from Mono Lake, California. Science (2008) 321:967-970
[25]Gorra R, Webster G, Martin M, et al. Dynamic microbial community associated with Iron-Arsenic co-precipitation products from a groundwater storage system in Bangladesh. Microb. Ecol. (2012) 64:171-186
[26]Oremland RS, Stolz JF. The ecology of arsenic. Science (2003) 300:939-944
[27]Islam FS, Gault AG, Boothman C, et al. Role of metal-reducing bacteria in arsenic release from Bengal delta sediments. Nature (2004) 430:68-71
[28]Fisher JC, Wallschlager D, Planer-Friedrich B, et al. A new role for sulfur in arsenic cycling. Environ. Sci. Technol. (2007) 42:81-85
[29]Guo H, Tang X, Yang S, et al. Effect of indigenous bacteria on geochemical behavior of arsenic in aquifer sediments from the Hetao Basin, Inner Mongolia:Evidence from sediment incubations. Appl. Geochem. (2008) 23:3267-3277
[30]Peters SC, Blum JD, Klaue B, et al. Arsenic occurrence in New Hampshire drinking water. Environ. Sci. Technol. (1999) 33:1328-1333
[31]Zobrist J, Dowdle PR, Davis JA, et al. Mobilization of arsenite by dissimilatory reduction of adsorbed arsenate. Environ. Sci. Technol. (2000) 34:4747-4753
[32]邓娅敏.河套盆地西部高砷地下水系统中的地球化学过程研究：博士学位论文.武汉：中国地质大学,2008
[33]Deng Y, Wang Y, Ma T, et al. Speciation and enrichment of arsenic in strongly reducing shallow aquifers at western Hetao Plain, northern China. Environ. Geol. (2009) 56: 1467-1477
[34]Guo H, Zhang B, Wang G, et al. Geochemical controls on arsenic and rare earth elements approximately along a groundwater flow path in the shallow aquifer of the Hetao Basin, Inner Mongolia. Chem. Geol. (2010) 270:117-125
[35]Jia Y, Guo H. Hydrogeochemical zonation of deep groundwaters near Langshan Mountain of the Hetao Basin, Inner Mongolia. Procedia Earth Planetary Sci. (2013) 7: 393-396
[36]Smedley P, Kinniburgh D. A review of the source, behaviour and distribution of arsenic in natural waters. Appl. Geochem. (2002) 17:517-568
[37]Rodriguez-Lado L, Sun G, Berg M, et al. Groundwater arsenic contamination throughout China. Science (2013) 341:866-868
[38]Guo H, Yang S, Tang X, et al. Groundwater geochemistry and its implications for arsenic mobilization in shallow aquifers of the Hetao Basin, Inner Mongolia. Sci. Total Environ. (2008)393:131-144
[39]Zhang H, Ma D and Hu X. Arsenic pollution in groundwater from Hetao Area, China. Environ. Geol. (2002) 41:638-643
[40]Masscheleyn PH, Delaune RD and Patrick Jr WH. Effect of redox potential and pH on arsenic speciation and solubility in a contaminated soil. Environ. Sci. Technol. (1991) 25: 1414-1419
[41]Guo H, Zhang B and Zhang Y. Control of organic and iron colloids on arsenic partition and transport in high arsenic groundwaters in the Hetao basin, Inner Mongolia. Appl. Geochem. (2011) 26:360-370
[42]Park J, Lee J, Lee J-U, et al. Microbial effects on geochemical behavior of arsenic in As-contaminated sediments. J. Geochem. Explor. (2006) 88:134-138
[43]Lloyd JR, Oremland RS. Microbial transformations of arsenic in the environment:From soda lakes to aquifers. Elements (2006) 2:85-90
[44]Sun W, Sierra-Alvarez R, Milner L, et al. Arsenite and ferrous iron oxidation linked to chemolithotrophic denitrification for the immobilization of arsenic in anoxic environments. Environ. Sci. Technol. (2009) 43:6585-6591
[45]Baesman SM, Stolz JF, Kulp TR, et al. Enrichment and isolation of Bacillus beveridgei sp nov., a facultative anaerobic haloalkaliphile from Mono Lake, California, that respires oxyanions of tellurium, selenium, and arsenic. Extremophiles (2009) 13:695-705
[46]Guo H, Stuben D, Berner Z, et al. Adsorption of arsenic species from water using activated siderite-hematite column filters. J. Hazard. Mater. (2008) 151:628-635
[47]Cavalca L, Corsini A, Zaccheo P, et al. Microbial transformations of arsenic: perspectives for biological removal of arsenic from water. Future Microbiol. (2013) 8: 753-768
[48]Cummings DE, Caccavo F, Fendorf S, et al. Arsenic mobilization by the dissimilatory Fe (Ⅲ)-reducing bacterium Shewanella alga BrY. Environ. Sci. Technol. (1999) 33: 723-729
[49]Zhu W, Young LY, Yee N, et al. Sulfide-driven arsenic mobilization from arsenopyrite and black shale pyrite. Geochim. Cosmochim. Acta (2008) 72:5243-5250
[50]Saalfield SL, Bostick BC. Changes in iron, sulfur, and arsenic speciation associated with bacterial sulfate reduction in ferrihydrite-rich systems. Environ. Sci. Technol. (2009) 43: 8787-8793
[51]Oremland RS, Saltikov CW, Wolfe-Simon F, et al. Arsenic in the evolution of earth and extraterrestrial ecosystems. Geomicrobiol. J. (2009) 26:522-536
[52]Handley KM, McBeth JM, Charnock JM, et al. Effect of iron redox transformations on arsenic solid-phase associations in an arsenic-rich, ferruginous hydrothermal sediment. Geochim. Cosmochim. Acta (2012) 102:124-142
[53]Kocar BD, Borch T and Fendorf S. Arsenic repartitioning during biogenic sulfidization and transformation of ferrihydrite. Geochim. Cosmochim. Acta (2010) 74:980-994
[54]Kirk MF, Holm TR, Park J, et al. Bacterial sulfate reduction limits natural arsenic contamination in groundwater. Geology (2004) 32:953-956
[55]Buschmann J, Berg M. Impact of sulfate reduction on the scale of arsenic contamination in groundwater of the Mekong, Bengal and Red River deltas. Appl. Geochem. (2009) 24: 1278-1286
[56]Mukherjee A, Bhattacharya P, Shi F, et al. Chemical evolution in the high arsenic groundwater of the Huhhot basin (Inner Mongolia, PR China) and its difference from the western Bengal basin (India). Appl. Geochem. (2009) 24:1835-1851
[57]Senn DB, Hemond HF. Nitrate controls on iron and arsenic in an urban lake. Science (2002) 296:2373-2376
[58]杨素珍.内蒙古河套平原原生高砷地下水的分布与形成机理研究：博士学位论文.北京：中国地质大学,2008
[59]何薪.河套平原农业灌溉影响下地下水中砷迁移富集规律研究：博士学位论文.武汉：中国地质大学,2010
[60]Guo H, Liu C, Lu H, et al. Pathways of coupled arsenic and iron cycling in high arsenic groundwater of the Hetao basin, Inner Mongolia, China:An iron isotope approach. Geochim. Cosmochim. Acta (2013) 112:130-145
[61]Hagiwara H, Akai J, Terasaki K, et al. Black colored sandy sediments caused by bacterial action, and the mechanism for arsenic enrichment of groundwater in Inner Mongolia. Appl. Geochem. (2011) 26:380-393
[62]Stahl DA, Lane DJ, Olsen GJ, et al. Analysis of hydrothermal vent-associated symbionts by ribosomal RNA sequences. Science (1984) 224:409-411
[63]Muyzer G, De Waal EC and Uitterlinden AG. Profiling of complex microbial populations by denaturing gradient gel electrophoresis analysis of polymerase chain reaction-amplified genes coding for 16S rRNA. Appl. Environ. Microbiol. (1993) 59: 695-700
[64]O'Sullivan LA, Sass AM, Webster G, et al. Contrasting relationships between biogeochemistry and prokaryotic diversity depth profiles along an estuarine sediment gradient. FEMS Microbiol. Ecol. (2013) 85:143-157
[65]Baker BJ, Sheik CS, Taylor CA, et al. Community transcriptomic assembly reveals microbes that contribute to deep-sea carbon and nitrogen cycling. ISME J. (2013)
[66]Caporaso JG, Lauber CL, Walters WA, et al. Ultra-high-throughput microbial community analysis on the Illumina HiSeq and MiSeq platforms. The ISME J. (2012) 6: 1621-1624
[67]Highlander SK. High throughput sequencing methods for microbiome profiling: application to food animal systems. Anim. Health Res. Rev. (2012) 13:40-53
[68]Jiang X-T, Peng X, Deng G-H, et al. Illumina sequencing of 16S rRNA tag revealed spatial variations of bacterial communities in a mangrove wetland. Microb. Ecol. (2013): 1-9
[69]Agrawal A, Lal B. Rapid detection and quantification of bisulfite reductase genes in oil field samples using real-time PCR. FEMS Microbiol. Ecol. (2009) 69:301-312
[70]Jiang H, Dong H, Yu B, et al. Abundance and diversity of aerobic anoxygenic phototrophic bacteria in saline lakes on the Tibetan plateau. FEMS Microbiol. Ecol. (2009)67:268-278
[71]Nunoura T, Oida H, Toki T, et al. Quantification of mcrA by quantitative fluorescent PCR in sediments from methane seep of the Nankai Trough. FEMS Microbiol. Ecol. (2006) 57:149-157
[72]Jones GW, Pichler T. Relationship between pyrite stability and arsenic mobility during aquifer storage and recovery in southwest central Florida. Environ. Sci. Technol. (2007) 41:723-730
[73]Arnds J, Knittel K, Buck U, et al. Development of a 16S rRNA-targeted probe set for Verrucomicrobia and its application for fluorescence in situ hybridization in a humic lake. Syst. Appl. Microbiol. (2010) 33:139-148
[74]Schmidt H, Eickhorst T. Detection and quantification of native microbial populations on soil-grown rice roots by catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). FEMS Microbiol. Ecol. (2013) 87:390-402
[75]Gentry T, Wickham G, Schadt C, et al. Microarray applications in microbial ecology research. Microb. Ecol. (2006) 52:159-175
[76]Zhang Z, Zhao X, Liang Y, et al. Microbial functional genes reveal selection of microbial community by PAHs in polluted soils. Environ. Chem. Lett. (2013) 11:11-17
[77]Marshall IP, Berggren DR, Azizian MF, et al. The Hydrogenase Chip:a tiling oligonucleotide DNA microarray technique for characterizing hydrogen-producing and-consuming microbes in microbial communities. The ISME J. (2012) 6:814-826
[78]Dowling CB, Poreda RJ, Basu AR, et al. Geochemical study of arsenic release mechanisms in the Bengal Basin groundwater. Water Resour. Res. (2002) 38:1273-1290
[79]Postma D, Jessen S, Hue NTM, et al. Mobilization of arsenic and iron from Red River floodplain sediments, Vietnam. Geochim. Cosmochim. Acta (2010) 74:3367-3381
[80]Guo H, Shen Z, Zhang Y, et al. Geochemical comparison of high and low arsenic groundwater in the Hetao Basin, Inner Mongolia. Procedia Earth Planetary Sci. (2013) 7: 313-316
[81]Deng Y, Wang Y, Ma T, et al. Arsenic associations in sediments from shallow aquifers of northwestern Hetao Basin, Inner Mongolia. Environ. Earth. Sci. (2011) 64:2001-2011
[82]Ruiz-Chancho M, Lopez-Sanchez J and Rubio R. Analytical speciation as a tool to assess arsenic behaviour in soils polluted by mining. Anal. Bioanal.Chem. (2007) 387: 627-635
[83]Yuan C, Jiang G and He B. Evaluation of the extraction methods for arsenic speciation in rice straw, Oryza sativa L., and analysis by HPLC-HG-AFS. J. Anal. At. Spectrom. (2005)20:103-110
[84]Giral M, Zagury GJ, Deschenes L, et al. Comparison of four extraction procedures to assess arsenate and arsenite species in contaminated soils. Environ. Pollut. (2010) 158: 1890-1898
[85]Li P, Wang Y, Jiang Z, et al. Microbial diversity in high arsenic groundwater in Hetao Basin of Inner Mongolia, China. Geomicrobiol. J. (2013) 30:897-909
[86]周文树,房建设.微波消解-电感耦合等离子体-原子发射光谱法测定剩余污泥中的全硫.分析仪器(2008)：18-20
[87]白云飞.土壤底泥中砷形态提取与水样中砷形态保存实验研究：硕士学位论文.北京：中国地质大学,2007
[88]Reza AHMS, Jean J-S, Lee M-K, et al. Implications of organic matter on arsenic mobilization into groundwater:Evidence from northwestern (Chapai-Nawabganj), central (Manikganj) and southeastern (Chandpur) Bangladesh. Water Res. (2010) 44: 5556-5574
[89]Barringer JL, Mumford A, Young LY, et al. Pathways for arsenic from sediments to groundwater to streams:Biogeochemical processes in the Inner Coastal Plain, New Jersey, USA. Water Res. (2010) 44:5532-5544
[90]Pedersen HD, Postma D and Jakobsen R. Release of arsenic associated with the reduction and transformation of iron oxides. Geochim. Cosmochim. Acta (2006) 70: 4116-4129
[91]Farooq S, Chandrasekharam D, Norra S, et al. Temporal variations in arsenic concentration in the groundwater of Murshidabad District, West Bengal, India. Environ. Earth. Sci. (2011) 62:223-232
[92]Oremland RS, Stolz JF and Hollibaugh JT. The microbial arsenic cycle in Mono Lake, California. FEMS Microbiol. Ecol. (2004) 48:15-27
[93]Oremland RS, Stolz JF. Arsenic, microbes and contaminated aquifers. Trends. Microbiol. (2005) 13:45-49
[94]Mumford AC, Barringer JL, Benzel WM, et al. Microbial transformations of arsenic: Mobilization from glauconitic sediments to water. Water Res. (2012) 46:2859-2868
[95]Guo H, Zhang Y, Jia Y, et al. Dynamic behaviors of water levels and arsenic concentration in shallow groundwater from the Hetao Basin, Inner Mongolia. J. Geochem. Explor. (2013) 135:130-140
[96]Thompson JR, Marcelino LA and Polz MF. Heteroduplexes in mixed-template amplifications:formation, consequence and elimination by 'reconditioning PCR'. Nucleic Acids Res. (2002) 30:2083-2088
[97]Webster G, Newberry CJ, Fry JC, et al. Assessment of bacterial community structure in the deep sub-seafloor biosphere by 16S rDNA-based techniques:a cautionary tale. J Microbiol Methods (2003) 55:155-164
[98]Marchesi JR, Sato T, Weightman AJ, et al. Design and evaluation of useful bacterium-specific PCR primers that amplify genes coding for bacterial 16S rRNA. Appl. Environ. Microbiol. (1998) 64:795-799
[99]DeLong EF. Archaea in coastal marine environments. Proc. Nat. Aca. Sci. (1992) 89: 5685-5689
[100]Nicol GW, Glover LA and Prosser JI. The impact of grassland management on archaeal community structure in upland pasture rhizosphere soil. Environ. Microbiol. (2003) 5: 152-162
[101]Li P, Wang Y, Liu K, et al. Bacterial community structure and diversity during establishment of an anaerobic bioreactor to treat swine wastewater. Water Sci. Technol. (2010)61:243-252
[102]Cavalca L, Zanchi R, Corsini A, et al. Arsenic-resistant bacteria associated with roots of the wild Cirsium arvense (L.) plant from an arsenic polluted soil, and screening of potential plant growth-promoting characteristics. Syst. Appl. Microbiol. (2010) 33: 154-164
[103]Achour AR, Bauda P and Billard P. Diversity of arsenite transporter genes from arsenic-resistant soil bacteria. Res. Microbiol. (2007) 158:128-137
[104]Chen C, Ho K, Liu F, et al. Autotrophic and heterotrophic denitrification by a newly isolated strain Pseudomonas sp. C27. Bioresour. Technol. (2013) 145:351-356
[105]Haaijer SCM, Lamers LPM, Smolders AJP, et al. Iron sulfide and pyrite as potential electron donors for microbial nitrate reduction in freshwater wetlands. Geomicrobiol. J. (2007)24:391-401
[106]Sutton NB, van der Kraan GM, van Loosdrecht M, et al. Characterization of geochemical constituents and bacterial populations associated with As mobilization in deep and shallow tube wells in Bangladesh. Water Res. (2009) 43:1720-1730
[107]Al Lawati WM, Rizoulis A, Eiche E, et al. Characterisation of organic matter and microbial communities in contrasting arsenic-rich Holocene and arsenic-poor Pleistocene aquifers, Red River Delta, Vietnam. Appl. Geochem. (2012) 27:315-325
[108]Farooq S, Chandrasekharam D, Abbt-Braun G, et al. Dissolved organic carbon from the traditional jute processing technique and its potential influence on arsenic enrichment in the Bengal Delta. Appl. Geochem. (2012) 27:292-303
[109]Hollibaugh JT, Budinoff C, Hollibaugh RA, et al. Sulfide oxidation coupled to arsenate reduction by a diverse microbial community in a soda lake. Appl. Environ. Microb. (2006) 72:2043-2049
[110]Groudieva T, Kambourova M, Yusef H, et al. Diversity and cold-active hydrolytic enzymes of culturable bacteria associated with Arctic sea ice, Spitzbergen. Extremophiles (2004) 8:475-488
[111]Knoblauch C, Sahm K and J(?)rgensen BB. Psychrophilic sulfate-reducing bacteria isolated from permanently cold Arctic marine sediments:description of Desulfofrigus oceanense gen. nov., sp. nov., Desulfofrigus fragile sp. nov., Desulfofaba gelida gen. nov., sp. nov., Desulfotalea psychrophila gen. nov., sp. nov. and Desulfotalea arctica sp. nov. Int. J. Syst. Evol. Micr. (1999) 49:1631-1643
[112]Shelobolina E, Konishi H, Xu H, et al. Isolation of phyllosilicate-iron redox cycling microorganisms from an illite-smectite rich hydromorphic soil. Front Microbiol (2012) 3: 134-143
[113]Kellermann C, Griebler C. Thiobacillus thiophilus sp. nov., a chemolithoautotrophic, thiosulfate-oxidizing bacterium isolated from contaminated aquifer sediments. Int. J. Syst. Evol. Micr. (2009) 59:583-588
[114]Oremland RS, Hoeft SE, Santini JA, et al. Anaerobic oxidation of arsenite in Mono Lake water and by facultative, arsenite-oxidizing chemoautotroph, strain MLHE-1. Appl. Environ. Microbiol. (2002) 68:4795-4802
[115]Salmassi TM, Venkateswaren K, Satomi M, et al. Oxidation of arsenite by Agrobacterium albertimagni, AOL15, sp. nov., isolated from Hot Creek, California. Geomicrobiol. J. (2002) 19:53-66
[116]Kojima H, Fukui M. Sulfuricella denitrificans gen. nov., sp. nov., a sulfur-oxidizing autotroph isolated from a freshwater lake. Int. J. Syst. Evol. Micr. (2010) 60:2862-2866
[117]Abraham WR, Strompl C, Meyer H, et al. Phylogeny and polyphasic taxonomy of Caulobacter species. Proposal of Maricaulis gen. nov. with Maricaulis maris (Poindexter) comb. nov. as the type species, and emended description of the genera Brevundimonas and Caulobacter. Int. J. Syst. Bacteriol. (1999) 49:1053-1073
[118]Inagaki F, Takai K, Kobayashi H, et al. Sulfurimonas autotrophica gen. nov., sp. nov., a novel sulfur-oxidizing ε-proteobacterium isolated from hydrothermal sediments in the Mid-Okinawa Trough. Int. J. Syst. Evol. Micr. (2003) 53:1801-1805
[119]Haaijer S, Van der Welle ME, Schmid MC, et al. Evidence for the involvement of betaproteobacterial Thiobacilli in the nitrate-dependent oxidation of iron sulfide minerals. FEMS Microbiol. Ecol. (2006) 58:439-448
[120]Muller D, Simeonova DD, Riegel P, et al. Herminiimonas arsenicoxydans sp. nov., a metalloresistant bacterium. Int. J. Syst. Evol. Micr. (2006) 56:1765-1769
[121]Quemeneur M, Heinrich-Salmeron A, Muller D, et al. Diversity surveys and evolutionary relationships of aoxB genes in aerobic arsenite-oxidizing bacteria. Appl. Environ. Microb. (2008) 74:4567-4573
[122]Garcia-Dominguez E, Mumford A, Rhine ED, et al. Novel autotrophic arsenite-oxidizing bacteria isolated from soil and sediments. FEMS Microbiol. Ecol. (2008) 66:401-410
[123]Haaijer SC, Crienen G, Jetten MS, et al. Anoxic iron cycling bacteria from an iron sulfide-and nitrate-rich freshwater environment. Front Microbiol (2012) 3:26-33
[124]Freikowski D, Winter J and Gallert C. Hydrogen formation by an arsenate-reducing Pseudomonas putida, isolated from arsenic-contaminated groundwater in West Bengal, India. Appl. Microbiol. Biotech. (2010) 88:1363-1371
[125]Srivastava D, Madamwar D and Subramanian R. Pentavalent arsenate reductase activity in cytosolic fractions of Pseudomonas sp., isolated from arsenic-contaminated sites of Tezpur, Assam. Appl. Biochem. Biotech. (2010) 162:766-779
[126]Procopio L, Alvarez VM, Jurelevicius DA, et al. Insight from the draft genome of Dietzia cinnamea P4 reveals mechanisms of survival in complex tropical soil habitats and biotechnology potential. Anton. Leeuw. Int. (2012) 101:289-302
[127]Pester M, Schleper C and Wagner M. The Thaumarchaeota:an emerging view of their phylogeny and ecophysiology. Curr. Opin. Microbiol. (2011) 14:300-306
[128]Chaganti SR, Lalman JA and Heath DD.16S rRNA gene based analysis of the microbial diversity and hydrogen production in three mixed anaerobic cultures. Int. J. Hydrogen Energy (2012) 37:9002-9017
[129]Meyer M, Stenzel U, Myles S, et al. Targeted high-throughput sequencing of tagged nucleic acid samples. Nucleic Acids Res. (2007) 35:e97
[130]Jones RT, Robeson MS, Lauber CL, et al. A comprehensive survey of soil acidobacterial diversity using pyrosequencing and clone library analyses. The ISME J. (2009) 3: 442-453
[131]Mackelprang R, Waldrop MP, DeAngelis KM, et al. Metagenomic analysis of a permafrost microbial community reveals a rapid response to thaw. Nature (2011) 480: 368-U120
[132]Lauber CL, Hamady M, Knight R, et al. Pyrosequencing-based assessment of soil pH as a predictor of soil bacterial community structure at the continental scale. Appl. Environ. Microb. (2009) 75:5111-5120
[133]Goldberg SM, Johnson J, Busam D, et al. A Sanger/pyrosequencing hybrid approach for the generation of high-quality draft assemblies of marine microbial genomes. Proc. Nat. Aca. Sci. (2006) 103:11240-11245
[134]Bates ST, Berg-Lyons D, Caporaso JG, et al. Examining the global distribution of dominant archaeal populations in soil. The ISME J. (2011) 5:908-917
[135]Caporaso JG, Kuczynski J, Stombaugh J, et al. QIIME allows analysis of high-throughput community sequencing data. Nat. Methods (2010) 7:335-336
[136]Magoc T, Salzberg SL. FLASH:fast length adjustment of short reads to improve genome assemblies. Bioinformatics (2011) 27:2957-2963
[137]Chessel D, Dufour AB and Thioulouse J. The ade4 package-I-One-table methods. R news (2004) 4:5-10
[138]Dray S, Dufour A-B. The ade4 package:implementing the duality diagram for ecologists. J. Stat. Softw. (2007) 22:1-20
[139]Clarke K,Warwick R. Similarity-based testing for community pattern:the two-way layout with no replication. Mar. Biol. (1994) 118:167-176
[140]Rhine ED, Phelps CD and Young L. Anaerobic arsenite oxidation by novel denitrifying isolates. Environ. Microbiol. (2006) 8:899-908
[141]Davolos D, Pietrangeli B. A molecular study on bacterial resistance to arsenic-toxicity in surface and underground waters of Latium (Italy). Ecotox. Environ, Safe. (2013) 96:1-9
[142]Jain R, Jha S, Adhikary H, et al. Isolation and molecular characterization of arsenite-tolerant Alishewanella sp. GIDC-5 originated from industrial effluents. Geomicrobiol. J. (2014) 31:82-90
[143]Shah R, Jha S. Alishewanella sp. strain GIDC-5, Arsenite hyper-tolerant bacteria isolated from industrial effluent of South Gujarat, India. Chem. Ecol. (2013) 29:427-436
[144]Dole dec S, Chessel D. Co-inertia analysis:an alternative method for studying species-environment relationships. Freshwater Biol. (1994) 31:277-294
[145]Dray S, Chessel D and Thioulouse J. Co-inertia analysis and the linking of ecological data tables. Ecology (2003) 84:3078-3089
[146]Luton PE, Wayne JM, Sharp RJ, et al. The mcrA gene as an alternative to 16S rRNA in the phylogenetic analysis of methanogen populations in landfill. Microbiology (2002) 148:3521-3530
[147]Bahr M, Crump BC, Klepac-Ceraj V, et al. Molecular characterization of sulfate-reducing bacteria in a New England salt marsh. Enviorn. Microbiol. (2005) 7: 1175-1185
[148]Rastogi G, Barua S, Sani RK, et al. Investigation of microbial populations in the extremely metal-contaminated Coeur d'Alene River sediments. Microb. Ecol. (2011) 62: 1-13
[149]Battaglia-Brunet F, Crouzet C, Burnol A, et al. Precipitation of arsenic sulphide from acidic water in a fixed-film bioreactor. Water Res. (2012) 46:3923-3933
[150]Zhang W, Ki J-S and Qian P-Y. Microbial diversity in polluted harbor sediments I: bacterial community assessment based on four clone libraries of 16S rDNA. Estuar. Coast. Shelf S. (2008) 76:668-681
[151]Macy JM, Santini JM, Pauling BV, et al. Two new arsenate/sulfate-reducing bacteria: mechanisms of arsenate reduction. Arch. Microbiol. (2000) 173:49-57
[152]Newman DK, Kennedy EK, Coates JD, et al. Dissimilatory arsenate and sulfate reduction in Desulfotomaculum auripigmentum sp. nov. Arch. Microbiol. (1997) 168: 380-388
[153]O'Day PA, Vlassopoulos D, Root R, et al. The influence of sulfur and iron on dissolved arsenic concentrations in the shallow subsurface under changing redox conditions. Proc. Nat. Aca. Sci. (2004) 101:13703-13708
[154]Bose P,Sharma A. Role of iron in controlling speciation and mobilization of arsenic in subsurface environment. Water Res. (2002) 36:4916-4926
[155]Varsanyi I, Kovacs LO. Arsenic, iron and organic matter in sediments and groundwater in the Pannonian Basin, Hungary. Appl. Geochem. (2006) 21:949-963
[156]Malasarn D, Saltikov C, Campbell K, et al. arrA is a reliable marker for As (V) respiration. Science (2004) 306:455-455
[157]Oremland RS, Stolz JF, Saltikov CW, et al. Anaerobic oxidation of arsenite by autotrophic bacteria:The view from Mono Lake, California. The Metabolism of Arsenite (2012):73-80
[158]Liao VHC, Chu YJ, Su YC, et al. Arsenite-oxidizing and arsenate-reducing bacteria associated with arsenic-rich groundwater in Taiwan. J. Contarn. Hydrol. (2011) 123: 20-29
[159]Wagner M, Roger AJ, Flax JL, et al. Phylogeny of dissimilatory sulfite reductases supports an early origin of sulfate respiration. J. Bacteriol. (1998) 180:2975-2982
[160]Geets J, Borremans B, Diels L, et al. DsrB gene-based DGGE for community and diversity surveys of sulfate-reducing bacteria. J. Microbiol. Meth. (2006) 66:194-205
[161]Song B, Chyun E, Jaffe PR, et al. Molecular methods to detect and monitor dissimilatory arsenate-respiring bacteria (DARB) in sediments. FEMS Microbiol. Ecol. (2009) 68: 108-117
[162]Hamamura N, Macur R, Korf S, et al. Linking microbial oxidation of arsenic with detection and phylogenetic analysis of arsenite oxidase genes in diverse geothermal environments. Environ. Microbiol. (2009) 11:421-431
[163]Steinberg LM,Regan JM. Phylogenetic comparison of the methanogenic communities from an acidic, oligotrophic fen and an anaerobic digester treating municipal wastewater sludge. Appl. Environ. Microbiol. (2008) 74:6663-6671
[164]O'Sullivan LA, Webster G, Fry JC, et al. Modified linker-PCR primers facilitate complete sequencing of DGGE DNA fragments. J. Microbiol. Meth. (2008) 75:579-581
[165]Takai K, Horikoshi K. Rapid detection and quantification of members of the archaeal community by quantitative PCR using fluorogenic probes. Appl. Environ. Microb. (2000) 66:5066-5072
[166]Suzuki MT, Taylor LT and DeLong EF. Quantitative analysis of small-subunit rRNA genes in mixed microbial populations via 5'-nuclease assays. Appl. Environ. Microb. (2000)66:4605-4614
[167]Stolz JF, Oremland RS. Bacterial respiration of arsenic and selenium. FEMS Microbiol. Rev. (1999) 23:615-627
[168]Dar SA, Yao L, van Dongen U, et al. Analysis of diversity and activity of sulfate-reducing bacterial communities in sulfidogenic bioreactors using 16S rRNA and dsrB genes as molecular markers. Appl. Environ. Microb. (2007) 73:594-604
[169]Jiang L, Zheng Y, Peng X, et al. Vertical distribution and diversity of sulfate-reducing prokaryotes in the Pearl River estuarine sediments, Southern China. FEMS Microbiol. Ecol. (2009)70:93-106
[170]Klappenbach JA, Saxman PR, Cole JR, et al. rrndb:the ribosomal RNA operon copy number database. Nucleic Acids Res. (2001) 29:181-184
[171]Brauer SL, Cadillo-Quiroz H, Ward RJ, et al. Methanoregula boonei gen. nov., sp. nov., an acidiphilic methanogen isolated from an acidic peat bog. Int. J. Syst. Evol. Micr. (2011)61:45-52
[172]lino T, Mori K and Suzuki K-i. Methanospirillum lacunae sp. nov., a methane-producing archaeon isolated from a puddly soil, and emended descriptions of the genus Methanospirillum and Methanospirillum hungatei. Int. J. Syst. Evol. Micr. (2010) 60: 2563-2566
[173]Imachi H, Sakai S, Sekiguchi Y, et al. Methanolinea tarda gen. nov., sp. nov., a methane-producing archaeon isolated from a methanogenic digester sludge. Int. J. Syst. Evol. Micr. (2008) 58:294-301
[174]Zhao Y, Boone DR, Mah RA, et al. Isolation and characterization of Methanocorpusculum labreanum sp. nov. from the LaBrea Tar Pits. Int. J. Syst. Bacteriol. (1989)39:10-13
[175]Barbier BA, Dziduch I, Liebner S, et al. Methane-cycling communities in a permafrost-affected soil on Herschel Island, Western Canadian Arctic:active layer profiling of mcrA and pmoA genes. FEMS Microbiol. Ecol. (2012) 82:287-302
[176]Zhu J, Liu X and Dong X. Methanobacterium movens sp. nov. and Methanobacterium flexile sp. nov., isolated from lake sediment. Int. J. Syst. Evol. Micr. (2011) 61: 2974-2978
[177]Steinberg LM, Regan JM. mcrA-targeted real-time quantitative PCR method to examine methanogen communities. Appl. Environ. Microbiol. (2009) 75:4435-4442
[178]Freitag TE, Prosser JI. Correlation of methane production and functional gene transcriptional activity in a peat soil. Appl. Environ. Microbiol. (2009) 75:6679-6687
[179]Finneran KT, Johnsen CV and Lovley DR. Rhodoferax ferrireducens sp. nov., a psychrotolerant, facultatively anaerobic bacterium that oxidizes acetate with the reduction of Fe (Ⅲ). Int. J. Syst. Evol. Micr. (2003) 53:669-673
[180]Sultana M, Vogler S, Zargar K, et al. New clusters of arsenite oxidase and unusual bacterial groups in enrichments from arsenic-contaminated soil. Arch. Microbiol. (2012) 194:623-635
[181]Ohtsuka T, Yamaguchi N, Makino T, et al. Arsenic dissolution from Japanese paddy soil by a dissimilatory arsenate-reducing bacterium Geobacter sp. OR-1. Environ. Sci. Technol. (2013) 47:6263-6271
[182]Perez-Jimenez JR, DeFraia C and Young L. Arsenate respiratory reductase gene arrA for Desulfosporosinus sp. strain Y5. Biochem. Biophys. Res. Commun. (2005) 338:825-829
[2]Fan H, Su C, Wang Y, et al. Sedimentary arsenite-oxidizing and arsenate-reducing bacteria associated with high arsenic groundwater from Shanyin, Northwestern China. J. Appl. Microbiol. (2008) 105:529-539
[3]Barringer JL, Reilly PA, Eberl DD, et al. Arsenic in sediments, groundwater, and streamwater of a glauconitic Coastal Plain terrain, New Jersey, USA-Chemical "fingerprints" for geogenic and anthropogenic sources. Appl. Geochem. (2011) 26: 763-776
[4]Bhattacharya P, Claesson M, Fagerberg J, et al. Natural arsenic in the groundwater of the alluvial aquifers of Santiago del Estero Province, Argentina. (2005):57-65
[5]Harvey CF, Swartz CH, Badruzzaman ABM, et al. Arsenic mobility and groundwater extraction in Bangladesh. Science (2002) 298:1602-1606
[6]Meharg AA, Scrimgeour C, Hossain SA, et al. Codeposition of organic carbon and arsenic in Bengal Delta aquifers. Environ. Sci. Technol. (2006) 40:4928-4935
[7]Winkel LH, Trang PTK, Lan VM, et al. Arsenic pollution of groundwater in Vietnam exacerbated by deep aquifer exploitation for more than a century. Proc. Nat. Aca. Sci. (2011)108:1246-1251
[8]Liu J, Zheng B, Aposhian HV, et al. Chronic arsenic poisoning from burning high-arsenic-containing coal in Guizhou, China. J. Peripher. Nerv. Syst. (2002) 7: 208-208
[9]Guo XJ, Fujino Y, Kaneko S, et al. Arsenic contamination of groundwater and prevalence of arsenical dermatosis in the Hetao plain area, Inner Mongolia, China. Mol. Cell. Biochem. (2001) 222:137-140
[10]Luo T, Hu S, Cui J, et al. Comparison of Arsenic geochemical evolution in the Datong Basin (Shanxi) and Hetao Basin (Inner Mongolia), China. Appl. Geochem. (2012) 27: 2315-2323
[11]Tseng C-H, Chong C-K, Tseng C-P, et al. Long-term arsenic exposure and ischemic heart disease in arseniasis-hyperendemic villages in Taiwan. Toxicol. Lett. (2003) 137:15-21
[12]Michael HA. An arsenic forecast for China. Science (2013) 341:852-853
[13]Ferreccio C, Sancha AM. Arsenic exposure and its impact on health in Chile. J. Health. Popul. Nutr. (2011) 24:164-175
[14]Jomova K, Jenisova Z, Feszterova M, et al. Arsenic:toxicity, oxidative stress and human disease. J. Appl. Toxicol. (2011) 31:95-107
[15]Knobeloch LM, Zierold KM and Anderson HA. Association of arsenic-contaminated drinking-water with prevalence of skin cancer in Wisconsin's Fox River Valley. J. Health. Popul. Nutr. (2011) 24:206-213
[16]胡立刚,蔡勇.砷的生物地球化学.化学进展(2009)：458-466
[17]Erban LE, Gorelick SM, Zebker HA, et al. Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence. Proc. Nat. Aca. Sci. (2013).
[18]Majumder S, Sarkar S, Chatterjee D, et al. Role of colloidal particles as scavengers of groundwater arsenic:A case study from rural Bengal. Procedia Earth Planetary Sci. (2013)7:546-549
[19]Radloff K, Zheng Y, Michael H, et al. Arsenic migration to deep groundwater in Bangladesh influenced by adsorption and water demand. Nat. Geosci. (2011) 4:793-798
[20]Routh J, Hjelmquist P. Distribution of arsenic and its mobility in shallow aquifer sediments from Ambikanagar, West Bengal, India. Appl. Geochem. (2011) 26:505-515
[21]Anawar HM, Akai J, Mihaljevic M, et al. Arsenic contamination in groundwater of Bangladesh:Perspectives on geochemical, microbial and anthropogenic Issues. Water (2011)3:1050-1076
[22]Nickson RT, McArthur JM, Ravenscroft P, et al. Mechanism of arsenic release to groundwater, Bangladesh and West Bengal. Appl. Geochem. (2000) 15:403-413
[23]Ahmed KM, Bhattacharya P, Hasan MA, et al. Arsenic enrichment in groundwater of the alluvial aquifers in Bangladesh:an overview. Appl. Geochem. (2004) 19:181-200
[24]Kulp TR, Hoeft SE, Asao M, et al. Arsenic(III) fuels anoxygenic photosynthesis in hot spring biofilms from Mono Lake, California. Science (2008) 321:967-970
[25]Gorra R, Webster G, Martin M, et al. Dynamic microbial community associated with Iron-Arsenic co-precipitation products from a groundwater storage system in Bangladesh. Microb. Ecol. (2012) 64:171-186
[26]Oremland RS, Stolz JF. The ecology of arsenic. Science (2003) 300:939-944
[27]Islam FS, Gault AG, Boothman C, et al. Role of metal-reducing bacteria in arsenic release from Bengal delta sediments. Nature (2004) 430:68-71
[28]Fisher JC, Wallschlager D, Planer-Friedrich B, et al. A new role for sulfur in arsenic cycling. Environ. Sci. Technol. (2007) 42:81-85
[29]Guo H, Tang X, Yang S, et al. Effect of indigenous bacteria on geochemical behavior of arsenic in aquifer sediments from the Hetao Basin, Inner Mongolia:Evidence from sediment incubations. Appl. Geochem. (2008) 23:3267-3277
[30]Peters SC, Blum JD, Klaue B, et al. Arsenic occurrence in New Hampshire drinking water. Environ. Sci. Technol. (1999) 33:1328-1333
[31]Zobrist J, Dowdle PR, Davis JA, et al. Mobilization of arsenite by dissimilatory reduction of adsorbed arsenate. Environ. Sci. Technol. (2000) 34:4747-4753
[32]邓娅敏.河套盆地西部高砷地下水系统中的地球化学过程研究：博士学位论文.武汉：中国地质大学,2008
[33]Deng Y, Wang Y, Ma T, et al. Speciation and enrichment of arsenic in strongly reducing shallow aquifers at western Hetao Plain, northern China. Environ. Geol. (2009) 56: 1467-1477
[34]Guo H, Zhang B, Wang G, et al. Geochemical controls on arsenic and rare earth elements approximately along a groundwater flow path in the shallow aquifer of the Hetao Basin, Inner Mongolia. Chem. Geol. (2010) 270:117-125
[35]Jia Y, Guo H. Hydrogeochemical zonation of deep groundwaters near Langshan Mountain of the Hetao Basin, Inner Mongolia. Procedia Earth Planetary Sci. (2013) 7: 393-396
[36]Smedley P, Kinniburgh D. A review of the source, behaviour and distribution of arsenic in natural waters. Appl. Geochem. (2002) 17:517-568
[37]Rodriguez-Lado L, Sun G, Berg M, et al. Groundwater arsenic contamination throughout China. Science (2013) 341:866-868
[38]Guo H, Yang S, Tang X, et al. Groundwater geochemistry and its implications for arsenic mobilization in shallow aquifers of the Hetao Basin, Inner Mongolia. Sci. Total Environ. (2008)393:131-144
[39]Zhang H, Ma D and Hu X. Arsenic pollution in groundwater from Hetao Area, China. Environ. Geol. (2002) 41:638-643
[40]Masscheleyn PH, Delaune RD and Patrick Jr WH. Effect of redox potential and pH on arsenic speciation and solubility in a contaminated soil. Environ. Sci. Technol. (1991) 25: 1414-1419
[41]Guo H, Zhang B and Zhang Y. Control of organic and iron colloids on arsenic partition and transport in high arsenic groundwaters in the Hetao basin, Inner Mongolia. Appl. Geochem. (2011) 26:360-370
[42]Park J, Lee J, Lee J-U, et al. Microbial effects on geochemical behavior of arsenic in As-contaminated sediments. J. Geochem. Explor. (2006) 88:134-138
[43]Lloyd JR, Oremland RS. Microbial transformations of arsenic in the environment:From soda lakes to aquifers. Elements (2006) 2:85-90
[44]Sun W, Sierra-Alvarez R, Milner L, et al. Arsenite and ferrous iron oxidation linked to chemolithotrophic denitrification for the immobilization of arsenic in anoxic environments. Environ. Sci. Technol. (2009) 43:6585-6591
[45]Baesman SM, Stolz JF, Kulp TR, et al. Enrichment and isolation of Bacillus beveridgei sp nov., a facultative anaerobic haloalkaliphile from Mono Lake, California, that respires oxyanions of tellurium, selenium, and arsenic. Extremophiles (2009) 13:695-705
[46]Guo H, Stuben D, Berner Z, et al. Adsorption of arsenic species from water using activated siderite-hematite column filters. J. Hazard. Mater. (2008) 151:628-635
[47]Cavalca L, Corsini A, Zaccheo P, et al. Microbial transformations of arsenic: perspectives for biological removal of arsenic from water. Future Microbiol. (2013) 8: 753-768
[48]Cummings DE, Caccavo F, Fendorf S, et al. Arsenic mobilization by the dissimilatory Fe (Ⅲ)-reducing bacterium Shewanella alga BrY. Environ. Sci. Technol. (1999) 33: 723-729
[49]Zhu W, Young LY, Yee N, et al. Sulfide-driven arsenic mobilization from arsenopyrite and black shale pyrite. Geochim. Cosmochim. Acta (2008) 72:5243-5250
[50]Saalfield SL, Bostick BC. Changes in iron, sulfur, and arsenic speciation associated with bacterial sulfate reduction in ferrihydrite-rich systems. Environ. Sci. Technol. (2009) 43: 8787-8793
[51]Oremland RS, Saltikov CW, Wolfe-Simon F, et al. Arsenic in the evolution of earth and extraterrestrial ecosystems. Geomicrobiol. J. (2009) 26:522-536
[52]Handley KM, McBeth JM, Charnock JM, et al. Effect of iron redox transformations on arsenic solid-phase associations in an arsenic-rich, ferruginous hydrothermal sediment. Geochim. Cosmochim. Acta (2012) 102:124-142
[53]Kocar BD, Borch T and Fendorf S. Arsenic repartitioning during biogenic sulfidization and transformation of ferrihydrite. Geochim. Cosmochim. Acta (2010) 74:980-994
[54]Kirk MF, Holm TR, Park J, et al. Bacterial sulfate reduction limits natural arsenic contamination in groundwater. Geology (2004) 32:953-956
[55]Buschmann J, Berg M. Impact of sulfate reduction on the scale of arsenic contamination in groundwater of the Mekong, Bengal and Red River deltas. Appl. Geochem. (2009) 24: 1278-1286
[56]Mukherjee A, Bhattacharya P, Shi F, et al. Chemical evolution in the high arsenic groundwater of the Huhhot basin (Inner Mongolia, PR China) and its difference from the western Bengal basin (India). Appl. Geochem. (2009) 24:1835-1851
[57]Senn DB, Hemond HF. Nitrate controls on iron and arsenic in an urban lake. Science (2002) 296:2373-2376
[58]杨素珍.内蒙古河套平原原生高砷地下水的分布与形成机理研究：博士学位论文.北京：中国地质大学,2008
[59]何薪.河套平原农业灌溉影响下地下水中砷迁移富集规律研究：博士学位论文.武汉：中国地质大学,2010
[60]Guo H, Liu C, Lu H, et al. Pathways of coupled arsenic and iron cycling in high arsenic groundwater of the Hetao basin, Inner Mongolia, China:An iron isotope approach. Geochim. Cosmochim. Acta (2013) 112:130-145
[61]Hagiwara H, Akai J, Terasaki K, et al. Black colored sandy sediments caused by bacterial action, and the mechanism for arsenic enrichment of groundwater in Inner Mongolia. Appl. Geochem. (2011) 26:380-393
[62]Stahl DA, Lane DJ, Olsen GJ, et al. Analysis of hydrothermal vent-associated symbionts by ribosomal RNA sequences. Science (1984) 224:409-411
[63]Muyzer G, De Waal EC and Uitterlinden AG. Profiling of complex microbial populations by denaturing gradient gel electrophoresis analysis of polymerase chain reaction-amplified genes coding for 16S rRNA. Appl. Environ. Microbiol. (1993) 59: 695-700
[64]O'Sullivan LA, Sass AM, Webster G, et al. Contrasting relationships between biogeochemistry and prokaryotic diversity depth profiles along an estuarine sediment gradient. FEMS Microbiol. Ecol. (2013) 85:143-157
[65]Baker BJ, Sheik CS, Taylor CA, et al. Community transcriptomic assembly reveals microbes that contribute to deep-sea carbon and nitrogen cycling. ISME J. (2013)
[66]Caporaso JG, Lauber CL, Walters WA, et al. Ultra-high-throughput microbial community analysis on the Illumina HiSeq and MiSeq platforms. The ISME J. (2012) 6: 1621-1624
[67]Highlander SK. High throughput sequencing methods for microbiome profiling: application to food animal systems. Anim. Health Res. Rev. (2012) 13:40-53
[68]Jiang X-T, Peng X, Deng G-H, et al. Illumina sequencing of 16S rRNA tag revealed spatial variations of bacterial communities in a mangrove wetland. Microb. Ecol. (2013): 1-9
[69]Agrawal A, Lal B. Rapid detection and quantification of bisulfite reductase genes in oil field samples using real-time PCR. FEMS Microbiol. Ecol. (2009) 69:301-312
[70]Jiang H, Dong H, Yu B, et al. Abundance and diversity of aerobic anoxygenic phototrophic bacteria in saline lakes on the Tibetan plateau. FEMS Microbiol. Ecol. (2009)67:268-278
[71]Nunoura T, Oida H, Toki T, et al. Quantification of mcrA by quantitative fluorescent PCR in sediments from methane seep of the Nankai Trough. FEMS Microbiol. Ecol. (2006) 57:149-157
[72]Jones GW, Pichler T. Relationship between pyrite stability and arsenic mobility during aquifer storage and recovery in southwest central Florida. Environ. Sci. Technol. (2007) 41:723-730
[73]Arnds J, Knittel K, Buck U, et al. Development of a 16S rRNA-targeted probe set for Verrucomicrobia and its application for fluorescence in situ hybridization in a humic lake. Syst. Appl. Microbiol. (2010) 33:139-148
[74]Schmidt H, Eickhorst T. Detection and quantification of native microbial populations on soil-grown rice roots by catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). FEMS Microbiol. Ecol. (2013) 87:390-402
[75]Gentry T, Wickham G, Schadt C, et al. Microarray applications in microbial ecology research. Microb. Ecol. (2006) 52:159-175
[76]Zhang Z, Zhao X, Liang Y, et al. Microbial functional genes reveal selection of microbial community by PAHs in polluted soils. Environ. Chem. Lett. (2013) 11:11-17
[77]Marshall IP, Berggren DR, Azizian MF, et al. The Hydrogenase Chip:a tiling oligonucleotide DNA microarray technique for characterizing hydrogen-producing and-consuming microbes in microbial communities. The ISME J. (2012) 6:814-826
[78]Dowling CB, Poreda RJ, Basu AR, et al. Geochemical study of arsenic release mechanisms in the Bengal Basin groundwater. Water Resour. Res. (2002) 38:1273-1290
[79]Postma D, Jessen S, Hue NTM, et al. Mobilization of arsenic and iron from Red River floodplain sediments, Vietnam. Geochim. Cosmochim. Acta (2010) 74:3367-3381
[80]Guo H, Shen Z, Zhang Y, et al. Geochemical comparison of high and low arsenic groundwater in the Hetao Basin, Inner Mongolia. Procedia Earth Planetary Sci. (2013) 7: 313-316
[81]Deng Y, Wang Y, Ma T, et al. Arsenic associations in sediments from shallow aquifers of northwestern Hetao Basin, Inner Mongolia. Environ. Earth. Sci. (2011) 64:2001-2011
[82]Ruiz-Chancho M, Lopez-Sanchez J and Rubio R. Analytical speciation as a tool to assess arsenic behaviour in soils polluted by mining. Anal. Bioanal.Chem. (2007) 387: 627-635
[83]Yuan C, Jiang G and He B. Evaluation of the extraction methods for arsenic speciation in rice straw, Oryza sativa L., and analysis by HPLC-HG-AFS. J. Anal. At. Spectrom. (2005)20:103-110
[84]Giral M, Zagury GJ, Deschenes L, et al. Comparison of four extraction procedures to assess arsenate and arsenite species in contaminated soils. Environ. Pollut. (2010) 158: 1890-1898
[85]Li P, Wang Y, Jiang Z, et al. Microbial diversity in high arsenic groundwater in Hetao Basin of Inner Mongolia, China. Geomicrobiol. J. (2013) 30:897-909
[86]周文树,房建设.微波消解-电感耦合等离子体-原子发射光谱法测定剩余污泥中的全硫.分析仪器(2008)：18-20
[87]白云飞.土壤底泥中砷形态提取与水样中砷形态保存实验研究：硕士学位论文.北京：中国地质大学,2007
[88]Reza AHMS, Jean J-S, Lee M-K, et al. Implications of organic matter on arsenic mobilization into groundwater:Evidence from northwestern (Chapai-Nawabganj), central (Manikganj) and southeastern (Chandpur) Bangladesh. Water Res. (2010) 44: 5556-5574
[89]Barringer JL, Mumford A, Young LY, et al. Pathways for arsenic from sediments to groundwater to streams:Biogeochemical processes in the Inner Coastal Plain, New Jersey, USA. Water Res. (2010) 44:5532-5544
[90]Pedersen HD, Postma D and Jakobsen R. Release of arsenic associated with the reduction and transformation of iron oxides. Geochim. Cosmochim. Acta (2006) 70: 4116-4129
[91]Farooq S, Chandrasekharam D, Norra S, et al. Temporal variations in arsenic concentration in the groundwater of Murshidabad District, West Bengal, India. Environ. Earth. Sci. (2011) 62:223-232
[92]Oremland RS, Stolz JF and Hollibaugh JT. The microbial arsenic cycle in Mono Lake, California. FEMS Microbiol. Ecol. (2004) 48:15-27
[93]Oremland RS, Stolz JF. Arsenic, microbes and contaminated aquifers. Trends. Microbiol. (2005) 13:45-49
[94]Mumford AC, Barringer JL, Benzel WM, et al. Microbial transformations of arsenic: Mobilization from glauconitic sediments to water. Water Res. (2012) 46:2859-2868
[95]Guo H, Zhang Y, Jia Y, et al. Dynamic behaviors of water levels and arsenic concentration in shallow groundwater from the Hetao Basin, Inner Mongolia. J. Geochem. Explor. (2013) 135:130-140
[96]Thompson JR, Marcelino LA and Polz MF. Heteroduplexes in mixed-template amplifications:formation, consequence and elimination by 'reconditioning PCR'. Nucleic Acids Res. (2002) 30:2083-2088
[97]Webster G, Newberry CJ, Fry JC, et al. Assessment of bacterial community structure in the deep sub-seafloor biosphere by 16S rDNA-based techniques:a cautionary tale. J Microbiol Methods (2003) 55:155-164
[98]Marchesi JR, Sato T, Weightman AJ, et al. Design and evaluation of useful bacterium-specific PCR primers that amplify genes coding for bacterial 16S rRNA. Appl. Environ. Microbiol. (1998) 64:795-799
[99]DeLong EF. Archaea in coastal marine environments. Proc. Nat. Aca. Sci. (1992) 89: 5685-5689
[100]Nicol GW, Glover LA and Prosser JI. The impact of grassland management on archaeal community structure in upland pasture rhizosphere soil. Environ. Microbiol. (2003) 5: 152-162
[101]Li P, Wang Y, Liu K, et al. Bacterial community structure and diversity during establishment of an anaerobic bioreactor to treat swine wastewater. Water Sci. Technol. (2010)61:243-252
[102]Cavalca L, Zanchi R, Corsini A, et al. Arsenic-resistant bacteria associated with roots of the wild Cirsium arvense (L.) plant from an arsenic polluted soil, and screening of potential plant growth-promoting characteristics. Syst. Appl. Microbiol. (2010) 33: 154-164
[103]Achour AR, Bauda P and Billard P. Diversity of arsenite transporter genes from arsenic-resistant soil bacteria. Res. Microbiol. (2007) 158:128-137
[104]Chen C, Ho K, Liu F, et al. Autotrophic and heterotrophic denitrification by a newly isolated strain Pseudomonas sp. C27. Bioresour. Technol. (2013) 145:351-356
[105]Haaijer SCM, Lamers LPM, Smolders AJP, et al. Iron sulfide and pyrite as potential electron donors for microbial nitrate reduction in freshwater wetlands. Geomicrobiol. J. (2007)24:391-401
[106]Sutton NB, van der Kraan GM, van Loosdrecht M, et al. Characterization of geochemical constituents and bacterial populations associated with As mobilization in deep and shallow tube wells in Bangladesh. Water Res. (2009) 43:1720-1730
[107]Al Lawati WM, Rizoulis A, Eiche E, et al. Characterisation of organic matter and microbial communities in contrasting arsenic-rich Holocene and arsenic-poor Pleistocene aquifers, Red River Delta, Vietnam. Appl. Geochem. (2012) 27:315-325
[108]Farooq S, Chandrasekharam D, Abbt-Braun G, et al. Dissolved organic carbon from the traditional jute processing technique and its potential influence on arsenic enrichment in the Bengal Delta. Appl. Geochem. (2012) 27:292-303
[109]Hollibaugh JT, Budinoff C, Hollibaugh RA, et al. Sulfide oxidation coupled to arsenate reduction by a diverse microbial community in a soda lake. Appl. Environ. Microb. (2006) 72:2043-2049
[110]Groudieva T, Kambourova M, Yusef H, et al. Diversity and cold-active hydrolytic enzymes of culturable bacteria associated with Arctic sea ice, Spitzbergen. Extremophiles (2004) 8:475-488
[111]Knoblauch C, Sahm K and J(?)rgensen BB. Psychrophilic sulfate-reducing bacteria isolated from permanently cold Arctic marine sediments:description of Desulfofrigus oceanense gen. nov., sp. nov., Desulfofrigus fragile sp. nov., Desulfofaba gelida gen. nov., sp. nov., Desulfotalea psychrophila gen. nov., sp. nov. and Desulfotalea arctica sp. nov. Int. J. Syst. Evol. Micr. (1999) 49:1631-1643
[112]Shelobolina E, Konishi H, Xu H, et al. Isolation of phyllosilicate-iron redox cycling microorganisms from an illite-smectite rich hydromorphic soil. Front Microbiol (2012) 3: 134-143
[113]Kellermann C, Griebler C. Thiobacillus thiophilus sp. nov., a chemolithoautotrophic, thiosulfate-oxidizing bacterium isolated from contaminated aquifer sediments. Int. J. Syst. Evol. Micr. (2009) 59:583-588
[114]Oremland RS, Hoeft SE, Santini JA, et al. Anaerobic oxidation of arsenite in Mono Lake water and by facultative, arsenite-oxidizing chemoautotroph, strain MLHE-1. Appl. Environ. Microbiol. (2002) 68:4795-4802
[115]Salmassi TM, Venkateswaren K, Satomi M, et al. Oxidation of arsenite by Agrobacterium albertimagni, AOL15, sp. nov., isolated from Hot Creek, California. Geomicrobiol. J. (2002) 19:53-66
[116]Kojima H, Fukui M. Sulfuricella denitrificans gen. nov., sp. nov., a sulfur-oxidizing autotroph isolated from a freshwater lake. Int. J. Syst. Evol. Micr. (2010) 60:2862-2866
[117]Abraham WR, Strompl C, Meyer H, et al. Phylogeny and polyphasic taxonomy of Caulobacter species. Proposal of Maricaulis gen. nov. with Maricaulis maris (Poindexter) comb. nov. as the type species, and emended description of the genera Brevundimonas and Caulobacter. Int. J. Syst. Bacteriol. (1999) 49:1053-1073
[118]Inagaki F, Takai K, Kobayashi H, et al. Sulfurimonas autotrophica gen. nov., sp. nov., a novel sulfur-oxidizing ε-proteobacterium isolated from hydrothermal sediments in the Mid-Okinawa Trough. Int. J. Syst. Evol. Micr. (2003) 53:1801-1805
[119]Haaijer S, Van der Welle ME, Schmid MC, et al. Evidence for the involvement of betaproteobacterial Thiobacilli in the nitrate-dependent oxidation of iron sulfide minerals. FEMS Microbiol. Ecol. (2006) 58:439-448
[120]Muller D, Simeonova DD, Riegel P, et al. Herminiimonas arsenicoxydans sp. nov., a metalloresistant bacterium. Int. J. Syst. Evol. Micr. (2006) 56:1765-1769
[121]Quemeneur M, Heinrich-Salmeron A, Muller D, et al. Diversity surveys and evolutionary relationships of aoxB genes in aerobic arsenite-oxidizing bacteria. Appl. Environ. Microb. (2008) 74:4567-4573
[122]Garcia-Dominguez E, Mumford A, Rhine ED, et al. Novel autotrophic arsenite-oxidizing bacteria isolated from soil and sediments. FEMS Microbiol. Ecol. (2008) 66:401-410
[123]Haaijer SC, Crienen G, Jetten MS, et al. Anoxic iron cycling bacteria from an iron sulfide-and nitrate-rich freshwater environment. Front Microbiol (2012) 3:26-33
[124]Freikowski D, Winter J and Gallert C. Hydrogen formation by an arsenate-reducing Pseudomonas putida, isolated from arsenic-contaminated groundwater in West Bengal, India. Appl. Microbiol. Biotech. (2010) 88:1363-1371
[125]Srivastava D, Madamwar D and Subramanian R. Pentavalent arsenate reductase activity in cytosolic fractions of Pseudomonas sp., isolated from arsenic-contaminated sites of Tezpur, Assam. Appl. Biochem. Biotech. (2010) 162:766-779
[126]Procopio L, Alvarez VM, Jurelevicius DA, et al. Insight from the draft genome of Dietzia cinnamea P4 reveals mechanisms of survival in complex tropical soil habitats and biotechnology potential. Anton. Leeuw. Int. (2012) 101:289-302
[127]Pester M, Schleper C and Wagner M. The Thaumarchaeota:an emerging view of their phylogeny and ecophysiology. Curr. Opin. Microbiol. (2011) 14:300-306
[128]Chaganti SR, Lalman JA and Heath DD.16S rRNA gene based analysis of the microbial diversity and hydrogen production in three mixed anaerobic cultures. Int. J. Hydrogen Energy (2012) 37:9002-9017
[129]Meyer M, Stenzel U, Myles S, et al. Targeted high-throughput sequencing of tagged nucleic acid samples. Nucleic Acids Res. (2007) 35:e97
[130]Jones RT, Robeson MS, Lauber CL, et al. A comprehensive survey of soil acidobacterial diversity using pyrosequencing and clone library analyses. The ISME J. (2009) 3: 442-453
[131]Mackelprang R, Waldrop MP, DeAngelis KM, et al. Metagenomic analysis of a permafrost microbial community reveals a rapid response to thaw. Nature (2011) 480: 368-U120
[132]Lauber CL, Hamady M, Knight R, et al. Pyrosequencing-based assessment of soil pH as a predictor of soil bacterial community structure at the continental scale. Appl. Environ. Microb. (2009) 75:5111-5120
[133]Goldberg SM, Johnson J, Busam D, et al. A Sanger/pyrosequencing hybrid approach for the generation of high-quality draft assemblies of marine microbial genomes. Proc. Nat. Aca. Sci. (2006) 103:11240-11245
[134]Bates ST, Berg-Lyons D, Caporaso JG, et al. Examining the global distribution of dominant archaeal populations in soil. The ISME J. (2011) 5:908-917
[135]Caporaso JG, Kuczynski J, Stombaugh J, et al. QIIME allows analysis of high-throughput community sequencing data. Nat. Methods (2010) 7:335-336
[136]Magoc T, Salzberg SL. FLASH:fast length adjustment of short reads to improve genome assemblies. Bioinformatics (2011) 27:2957-2963
[137]Chessel D, Dufour AB and Thioulouse J. The ade4 package-I-One-table methods. R news (2004) 4:5-10
[138]Dray S, Dufour A-B. The ade4 package:implementing the duality diagram for ecologists. J. Stat. Softw. (2007) 22:1-20
[139]Clarke K,Warwick R. Similarity-based testing for community pattern:the two-way layout with no replication. Mar. Biol. (1994) 118:167-176
[140]Rhine ED, Phelps CD and Young L. Anaerobic arsenite oxidation by novel denitrifying isolates. Environ. Microbiol. (2006) 8:899-908
[141]Davolos D, Pietrangeli B. A molecular study on bacterial resistance to arsenic-toxicity in surface and underground waters of Latium (Italy). Ecotox. Environ, Safe. (2013) 96:1-9
[142]Jain R, Jha S, Adhikary H, et al. Isolation and molecular characterization of arsenite-tolerant Alishewanella sp. GIDC-5 originated from industrial effluents. Geomicrobiol. J. (2014) 31:82-90
[143]Shah R, Jha S. Alishewanella sp. strain GIDC-5, Arsenite hyper-tolerant bacteria isolated from industrial effluent of South Gujarat, India. Chem. Ecol. (2013) 29:427-436
[144]Dole dec S, Chessel D. Co-inertia analysis:an alternative method for studying species-environment relationships. Freshwater Biol. (1994) 31:277-294
[145]Dray S, Chessel D and Thioulouse J. Co-inertia analysis and the linking of ecological data tables. Ecology (2003) 84:3078-3089
[146]Luton PE, Wayne JM, Sharp RJ, et al. The mcrA gene as an alternative to 16S rRNA in the phylogenetic analysis of methanogen populations in landfill. Microbiology (2002) 148:3521-3530
[147]Bahr M, Crump BC, Klepac-Ceraj V, et al. Molecular characterization of sulfate-reducing bacteria in a New England salt marsh. Enviorn. Microbiol. (2005) 7: 1175-1185
[148]Rastogi G, Barua S, Sani RK, et al. Investigation of microbial populations in the extremely metal-contaminated Coeur d'Alene River sediments. Microb. Ecol. (2011) 62: 1-13
[149]Battaglia-Brunet F, Crouzet C, Burnol A, et al. Precipitation of arsenic sulphide from acidic water in a fixed-film bioreactor. Water Res. (2012) 46:3923-3933
[150]Zhang W, Ki J-S and Qian P-Y. Microbial diversity in polluted harbor sediments I: bacterial community assessment based on four clone libraries of 16S rDNA. Estuar. Coast. Shelf S. (2008) 76:668-681
[151]Macy JM, Santini JM, Pauling BV, et al. Two new arsenate/sulfate-reducing bacteria: mechanisms of arsenate reduction. Arch. Microbiol. (2000) 173:49-57
[152]Newman DK, Kennedy EK, Coates JD, et al. Dissimilatory arsenate and sulfate reduction in Desulfotomaculum auripigmentum sp. nov. Arch. Microbiol. (1997) 168: 380-388
[153]O'Day PA, Vlassopoulos D, Root R, et al. The influence of sulfur and iron on dissolved arsenic concentrations in the shallow subsurface under changing redox conditions. Proc. Nat. Aca. Sci. (2004) 101:13703-13708
[154]Bose P,Sharma A. Role of iron in controlling speciation and mobilization of arsenic in subsurface environment. Water Res. (2002) 36:4916-4926
[155]Varsanyi I, Kovacs LO. Arsenic, iron and organic matter in sediments and groundwater in the Pannonian Basin, Hungary. Appl. Geochem. (2006) 21:949-963
[156]Malasarn D, Saltikov C, Campbell K, et al. arrA is a reliable marker for As (V) respiration. Science (2004) 306:455-455
[157]Oremland RS, Stolz JF, Saltikov CW, et al. Anaerobic oxidation of arsenite by autotrophic bacteria:The view from Mono Lake, California. The Metabolism of Arsenite (2012):73-80
[158]Liao VHC, Chu YJ, Su YC, et al. Arsenite-oxidizing and arsenate-reducing bacteria associated with arsenic-rich groundwater in Taiwan. J. Contarn. Hydrol. (2011) 123: 20-29
[159]Wagner M, Roger AJ, Flax JL, et al. Phylogeny of dissimilatory sulfite reductases supports an early origin of sulfate respiration. J. Bacteriol. (1998) 180:2975-2982
[160]Geets J, Borremans B, Diels L, et al. DsrB gene-based DGGE for community and diversity surveys of sulfate-reducing bacteria. J. Microbiol. Meth. (2006) 66:194-205
[161]Song B, Chyun E, Jaffe PR, et al. Molecular methods to detect and monitor dissimilatory arsenate-respiring bacteria (DARB) in sediments. FEMS Microbiol. Ecol. (2009) 68: 108-117
[162]Hamamura N, Macur R, Korf S, et al. Linking microbial oxidation of arsenic with detection and phylogenetic analysis of arsenite oxidase genes in diverse geothermal environments. Environ. Microbiol. (2009) 11:421-431
[163]Steinberg LM,Regan JM. Phylogenetic comparison of the methanogenic communities from an acidic, oligotrophic fen and an anaerobic digester treating municipal wastewater sludge. Appl. Environ. Microbiol. (2008) 74:6663-6671
[164]O'Sullivan LA, Webster G, Fry JC, et al. Modified linker-PCR primers facilitate complete sequencing of DGGE DNA fragments. J. Microbiol. Meth. (2008) 75:579-581
[165]Takai K, Horikoshi K. Rapid detection and quantification of members of the archaeal community by quantitative PCR using fluorogenic probes. Appl. Environ. Microb. (2000) 66:5066-5072
[166]Suzuki MT, Taylor LT and DeLong EF. Quantitative analysis of small-subunit rRNA genes in mixed microbial populations via 5'-nuclease assays. Appl. Environ. Microb. (2000)66:4605-4614
[167]Stolz JF, Oremland RS. Bacterial respiration of arsenic and selenium. FEMS Microbiol. Rev. (1999) 23:615-627
[168]Dar SA, Yao L, van Dongen U, et al. Analysis of diversity and activity of sulfate-reducing bacterial communities in sulfidogenic bioreactors using 16S rRNA and dsrB genes as molecular markers. Appl. Environ. Microb. (2007) 73:594-604
[169]Jiang L, Zheng Y, Peng X, et al. Vertical distribution and diversity of sulfate-reducing prokaryotes in the Pearl River estuarine sediments, Southern China. FEMS Microbiol. Ecol. (2009)70:93-106
[170]Klappenbach JA, Saxman PR, Cole JR, et al. rrndb:the ribosomal RNA operon copy number database. Nucleic Acids Res. (2001) 29:181-184
[171]Brauer SL, Cadillo-Quiroz H, Ward RJ, et al. Methanoregula boonei gen. nov., sp. nov., an acidiphilic methanogen isolated from an acidic peat bog. Int. J. Syst. Evol. Micr. (2011)61:45-52
[172]lino T, Mori K and Suzuki K-i. Methanospirillum lacunae sp. nov., a methane-producing archaeon isolated from a puddly soil, and emended descriptions of the genus Methanospirillum and Methanospirillum hungatei. Int. J. Syst. Evol. Micr. (2010) 60: 2563-2566
[173]Imachi H, Sakai S, Sekiguchi Y, et al. Methanolinea tarda gen. nov., sp. nov., a methane-producing archaeon isolated from a methanogenic digester sludge. Int. J. Syst. Evol. Micr. (2008) 58:294-301
[174]Zhao Y, Boone DR, Mah RA, et al. Isolation and characterization of Methanocorpusculum labreanum sp. nov. from the LaBrea Tar Pits. Int. J. Syst. Bacteriol. (1989)39:10-13
[175]Barbier BA, Dziduch I, Liebner S, et al. Methane-cycling communities in a permafrost-affected soil on Herschel Island, Western Canadian Arctic:active layer profiling of mcrA and pmoA genes. FEMS Microbiol. Ecol. (2012) 82:287-302
[176]Zhu J, Liu X and Dong X. Methanobacterium movens sp. nov. and Methanobacterium flexile sp. nov., isolated from lake sediment. Int. J. Syst. Evol. Micr. (2011) 61: 2974-2978
[177]Steinberg LM, Regan JM. mcrA-targeted real-time quantitative PCR method to examine methanogen communities. Appl. Environ. Microbiol. (2009) 75:4435-4442
[178]Freitag TE, Prosser JI. Correlation of methane production and functional gene transcriptional activity in a peat soil. Appl. Environ. Microbiol. (2009) 75:6679-6687
[179]Finneran KT, Johnsen CV and Lovley DR. Rhodoferax ferrireducens sp. nov., a psychrotolerant, facultatively anaerobic bacterium that oxidizes acetate with the reduction of Fe (Ⅲ). Int. J. Syst. Evol. Micr. (2003) 53:669-673
[180]Sultana M, Vogler S, Zargar K, et al. New clusters of arsenite oxidase and unusual bacterial groups in enrichments from arsenic-contaminated soil. Arch. Microbiol. (2012) 194:623-635
[181]Ohtsuka T, Yamaguchi N, Makino T, et al. Arsenic dissolution from Japanese paddy soil by a dissimilatory arsenate-reducing bacterium Geobacter sp. OR-1. Environ. Sci. Technol. (2013) 47:6263-6271
[182]Perez-Jimenez JR, DeFraia C and Young L. Arsenate respiratory reductase gene arrA for Desulfosporosinus sp. strain Y5. Biochem. Biophys. Res. Commun. (2005) 338:825-829
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