Holmes Dawn E, Finneran Kevin T, O'Neil Regina A, Lovley Derek R
Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Appl Environ Microbiol. 2002 May;68(5):2300-6. doi: 10.1128/AEM.68.5.2300-2306.2002.
Stimulating microbial reduction of soluble U(VI) to insoluble U(IV) shows promise as a strategy for immobilizing uranium in uranium-contaminated subsurface environments. In order to learn more about which microorganisms might be involved in U(VI) reduction in situ, the changes in the microbial community when U(VI) reduction was stimulated with the addition of acetate were monitored in sediments from three different uranium-contaminated sites in the floodplain of the San Juan River in Shiprock, N.Mex. In all three sediments U(VI) reduction was accompanied by concurrent Fe(III) reduction and a dramatic enrichment of microorganisms in the family Geobacteraceae, which are known U(VI)- and Fe(III)-reducing microorganisms. At the point when U(VI) reduction and Fe(III) reduction were nearing completion, Geobacteraceae accounted for ca. 40% of the 16S ribosomal DNA (rDNA) sequences recovered from the sediments with bacterial PCR primers, whereas Geobacteraceae accounted for fewer than 5% of the 16S rDNA sequences in control sediments that were not amended with acetate and in which U(VI) and Fe(III) reduction were not stimulated. Between 55 and 65% of these Geobacteraceae sequences were most similar to sequences from Desulfuromonas species, with the remainder being most closely related to Geobacter species. Quantitative analysis of Geobacteraceae sequences with most-probable-number PCR and TaqMan analyses indicated that the number of Geobacteraceae sequences increased from 2 to 4 orders of magnitude over the course of U(VI) and Fe(III) reduction in the acetate-amended sediments from the three sites. No increase in Geobacteraceae sequences was observed in control sediments. In contrast to the predominance of Geobacteraceae sequences, no sequences related to other known Fe(III)-reducing microorganisms were detected in sediments. These results compare favorably with an increasing number of studies which have demonstrated that Geobacteraceae are important components of the microbial community in a diversity of subsurface environments in which Fe(III) reduction is an important process. The combination of these results with the finding that U(VI) reduction takes place during Fe(III) reduction and prior to sulfate reduction suggests that Geobacteraceae will be responsible for much of the Fe(III) and U(VI) reduction during uranium bioremediation in these sediments.
刺激微生物将可溶性U(VI)还原为不溶性U(IV)，作为一种在铀污染的地下环境中固定铀的策略，显示出了前景。为了更多地了解原位U(VI)还原过程中可能涉及哪些微生物，在新墨西哥州希普罗克市圣胡安河漫滩三个不同铀污染场地的沉积物中，监测了添加乙酸盐刺激U(VI)还原时微生物群落的变化。在所有这三种沉积物中，U(VI)还原都伴随着同时发生的Fe(III)还原以及地杆菌科微生物的显著富集，地杆菌科是已知的U(VI)和Fe(III)还原微生物。当U(VI)还原和Fe(III)还原接近完成时，用地杆菌科细菌PCR引物从沉积物中回收的16S核糖体DNA（rDNA）序列中，地杆菌科约占40%，而在未添加乙酸盐且未刺激U(VI)和Fe(III)还原的对照沉积物中，地杆菌科在16S rDNA序列中所占比例不到5%。这些地杆菌科序列中，55%至65%与脱硫单胞菌属的序列最为相似，其余的与地杆菌属关系最为密切。用地杆菌科序列的最可能数PCR和TaqMan分析进行定量分析表明，在三个场地添加乙酸盐的沉积物中，在U(VI)和Fe(III)还原过程中，地杆菌科序列的数量增加了2到4个数量级。在对照沉积物中未观察到地杆菌科序列的增加。与地杆菌科序列占主导地位形成对比的是，在沉积物中未检测到与其他已知Fe(III)还原微生物相关的序列。这些结果与越来越多的研究结果相符，这些研究表明，地杆菌科是各种地下环境中微生物群落的重要组成部分，在这些环境中Fe(III)还原是一个重要过程。这些结果与U(VI)还原在Fe(III)还原期间且在硫酸盐还原之前发生这一发现相结合，表明地杆菌科将在这些沉积物的铀生物修复过程中负责大部分的Fe(III)和U(VI)还原。
