Microbial Community in High Arsenic Shallow Aquifers in Hetao Basin of Inner Mongolia, China by 454 Pyrosequencing

A comprehensive survey of microbial community with 454 Pyrosequencing was carried out in 20 groundwater samples (4 low and 16 high arsenic groundwater) and 19 sediments from three boreholes (two high arsenic boreholes and one low arsenic borehole) in a high arsenic groundwater system located in Hetao Basin, Inner Mongolia by. A total of 233,704 reads and 12-267 species-level OTUs were detected. Richness and diversity of microbial communities in high arsenic sediments are higher than those in high arsenic groundwater. Microbial community structure was significantly different either between low arsenic and high arsenic samples or between groundwater and sediments. Acinetobacter, Pseudomonas, Psychrobacter and Alishewanella were the top four predominant populations in high arsenic groundwater, while Thiobacillus, Pseudomonas, Hydrogenophaga, Enterobacteriaceae, Sulfuricurvum and Arthrobacter were distinctly dominated in high arsenic sediments. Acinetobacter was distinctly dominated in groundwater with the markedly high relative abundance (average 62.41%), and Thiobacillus was significantly abundant (average abundance 24.62%) in sediments. Archaeal sequences of high arsenic groundwater were mostly related to methanogens. Groundwater and sediment samples were divided into low and high arsenic groups based on geochemical parameters and microbial communities by hierarchical clustering and PCoA analyses. This suggested that arsenic is a critical environmental factor that contributes to the difference microbial community structure. BIO-ENV and co-inertia analyses showed that some other geochemical parameters including TOC, SO42-, SO42-/TS and Fe2+ were also the important factors causing the difference of the microbial community. The results of this study expand our current understanding of microbial ecology in high arsenic aquifers and emphasize the potential importance of microbes in arsenic mobilization in the shallow aquifers of Hetao Basin, Inner Mongolia.

本研究针对内蒙古河套盆地某高砷地下水系统，采用454焦磷酸测序（454 Pyrosequencing）技术对微生物群落开展了全面调研：共采集20件地下水样品（其中低砷地下水4件、高砷地下水16件），以及来自3个钻孔（2个高砷钻孔、1个低砷钻孔）的19件沉积物样品。本次测序共获得233704条读段（reads），并鉴定得到12~267个物种级操作分类单元（OTUs）。高砷沉积物中的微生物群落丰富度与多样性均高于高砷地下水。无论低砷与高砷样品之间，还是地下水与沉积物之间，微生物群落结构均存在显著差异。高砷地下水中的优势菌群前四位依次为不动杆菌属（Acinetobacter）、假单胞菌属（Pseudomonas）、嗜冷杆菌属（Psychrobacter）以及阿里谢瓦菌属（Alishewanella）；而高砷沉积物中的优势菌群则以硫杆菌属（Thiobacillus）、假单胞菌属、噬氢菌属（Hydrogenophaga）、肠杆菌科（Enterobacteriaceae）、硫弯曲菌属（Sulfuricurvum）和节杆菌属（Arthrobacter）为主。地下水中以不动杆菌属为绝对优势类群，其相对丰度均值高达62.41%；沉积物中则以硫杆菌属为优势类群，平均相对丰度达24.62%。高砷地下水中的古菌序列大多与产甲烷菌相关。通过层级聚类（hierarchical clustering）与主坐标分析（PCoA），基于地球化学参数与微生物群落特征，可将地下水与沉积物样品划分为低砷组与高砷组。这表明砷是驱动微生物群落结构产生差异的关键环境因子。BIO-ENV与共惯量分析（co-inertia）结果显示，总有机碳（TOC, Total Organic Carbon）、硫酸根（SO₄²⁻）、硫酸根/总硫比值（SO₄²⁻/TS）以及亚铁离子（Fe²⁺）等其他地球化学参数，同样是影响微生物群落结构差异的重要因素。本研究结果拓展了我们对高砷含水层微生物生态的现有认知，并强调了内蒙古河套盆地浅层含水层中微生物在砷迁移活化过程中的潜在重要性。