Vrionis Helen A, Anderson Robert T, Ortiz-Bernad Irene, O'Neill Kathleen R, Resch Charles T, Peacock Aaron D, Dayvault Richard, White David C, Long Philip E, Lovley Derek R
Department of Microbiology, Morrill Science IVN, University of Massachusetts, Amherst, MA 01003, USA.
Appl Environ Microbiol. 2005 Oct;71(10):6308-18. doi: 10.1128/AEM.71.10.6308-6318.2005.
The geochemistry and microbiology of a uranium-contaminated subsurface environment that had undergone two seasons of acetate addition to stimulate microbial U(VI) reduction was examined. There were distinct horizontal and vertical geochemical gradients that could be attributed in large part to the manner in which acetate was distributed in the aquifer, with more reduction of Fe(III) and sulfate occurring at greater depths and closer to the point of acetate injection. Clone libraries of 16S rRNA genes derived from sediments and groundwater indicated an enrichment of sulfate-reducing bacteria in the order Desulfobacterales in sediment and groundwater samples. These samples were collected nearest the injection gallery where microbially reducible Fe(III) oxides were highly depleted, groundwater sulfate concentrations were low, and increases in acid volatile sulfide were observed in the sediment. Further down-gradient, metal-reducing conditions were present as indicated by intermediate Fe(II)/Fe(total) ratios, lower acid volatile sulfide values, and increased abundance of 16S rRNA gene sequences belonging to the dissimilatory Fe(III)- and U(VI)-reducing family Geobacteraceae. Maximal Fe(III) and U(VI) reduction correlated with maximal recovery of Geobacteraceae 16S rRNA gene sequences in both groundwater and sediment; however, the sites at which these maxima occurred were spatially separated within the aquifer. The substantial microbial and geochemical heterogeneity at this site demonstrates that attempts should be made to deliver acetate in a more uniform manner and that closely spaced sampling intervals, horizontally and vertically, in both sediment and groundwater are necessary in order to obtain a more in-depth understanding of microbial processes and the relative contribution of attached and planktonic populations to in situ uranium bioremediation.
对一个受铀污染的地下环境进行了地球化学和微生物学研究，该环境已添加醋酸盐两个季节以刺激微生物对U(VI)的还原作用。存在明显的水平和垂直地球化学梯度，这在很大程度上可归因于醋酸盐在含水层中的分布方式，在更深且更靠近醋酸盐注入点的地方，Fe(III)和硫酸盐的还原作用更强。从沉积物和地下水中提取的16S rRNA基因克隆文库表明，在沉积物和地下水样本中，脱硫杆菌目硫酸盐还原菌富集。这些样本是在最靠近注入廊道的地方采集的，那里可被微生物还原的Fe(III)氧化物高度耗尽，地下水中硫酸盐浓度较低，且在沉积物中观察到酸挥发性硫化物增加。在下游更远的地方，存在金属还原条件，表现为中等的Fe(II)/Fe(总)比值、较低的酸挥发性硫化物值以及属于异化Fe(III)和U(VI)还原菌科地杆菌科的16S rRNA基因序列丰度增加。最大的Fe(III)和U(VI)还原与地杆菌科16S rRNA基因序列在地下水和沉积物中的最大回收率相关；然而，这些最大值出现的位置在含水层内空间上是分开的。该地点显著的微生物和地球化学异质性表明，应尝试以更均匀的方式输送醋酸盐，并且在沉积物和地下水中水平和垂直方向上进行紧密间隔的采样是必要的，以便更深入地了解微生物过程以及附着和浮游种群对原位铀生物修复的相对贡献。
