Environmental and Life Sciences Graduate Program, Department of Chemistry, Trent University, 1600 West Bank Drive, Peterborough, Ontario, Canada K9J 7B8.
Chemosphere. 2011 Feb;82(6):911-6. doi: 10.1016/j.chemosphere.2010.10.050. Epub 2010 Nov 11.
Sulfate reducing bacteria (SRB) are important mercury methylators in sediments, but information on mercury methylators in other compartments is ambiguous. To investigate SRB involvement in methylation in Amazonian periphyton, the relationship between Hg methylation potential and SRB (Desulfobacteraceae, Desulfobulbaceae and Desulfovibrionaceae) abundance in Eichhornia crassipes and Polygonum densiflorum root associated periphyton was examined. Periphyton subsamples of each macrophyte were amended with electron donors (lactate, acetate and propionate) or inhibitors (molybdate) of sulfate reduction to create differences in SRB subgroup abundance, which was measured by quantitative real-time PCR with primers specific for the 16S rRNA gene. Mercury methylation and demethylation potentials were determined by a stable isotope tracer technique using 200HgCl and CH3(202)HgCl, respectively. Relative abundance of Desulfobacteraceae (<0.01-12.5%) and Desulfovibrionaceae (0.01-6.8%) were both highly variable among samples and subsamples, but a significant linear relationship (p<0.05) was found between Desulfobacteraceae abundance and net methylmercury formation among treatments of the same macrophyte periphyton and among all P. densiflorum samples, suggesting that Desulfobacteraceae bacteria are the most important mercury methylators among SRB families. Yet, molybdate only partially inhibited mercury methylation potentials, suggesting the involvement of other microorganisms as well. The response of net methylmercury production to the different electron donors and molybdate was highly variable (3-1104 pg g(-1) in 12 h) among samples, as was the net formation in control samples (17-164 pg g(-1) in 12 h). This demonstrates the importance of community variability and complexity of microbial interactions for the overall methylmercury production in periphyton and their response to external stimulus.
硫酸盐还原菌 (SRB) 是沉积物中重要的汞甲基化菌，但其他环境中汞甲基化菌的信息尚不清楚。为了研究亚马逊河沿岸水生植物附生生物中硫酸盐还原菌 (脱硫杆菌科、脱硫球杆菌科和脱硫弧菌科) 与汞甲基化之间的关系，本研究检测了凤眼莲和密齿酸模根相关附生生物中 Hg 甲基化潜能与 SRB 丰度的关系。通过定量实时 PCR 用特定 16S rRNA 基因的引物来测量 SRB 亚群丰度，为每个大型植物的附生生物亚样本添加电子供体（乳酸盐、醋酸盐和丙酸盐）或硫酸盐还原抑制剂（钼酸盐）以产生 SRB 亚群丰度的差异。通过使用 200HgCl 和 CH3(202)HgCl 进行稳定同位素示踪技术，分别测定汞的甲基化和去甲基化潜能。尽管脱硫杆菌科 (<0.01-12.5%) 和脱硫弧菌科 (0.01-6.8%) 的相对丰度在样品和亚样品之间变化很大，但在同一大型植物附生生物的处理和所有密齿酸模根样本中，脱硫杆菌科丰度与净甲基汞形成之间存在显著的线性关系 (p<0.05)，这表明脱硫杆菌科细菌是 SRB 家族中最重要的汞甲基化菌。然而，钼酸盐仅部分抑制了汞的甲基化潜能，这表明其他微生物也参与其中。不同电子供体和钼酸盐对净甲基汞生成的响应在样品之间变化很大 (12 小时内 3-1104 pg g(-1))，在对照样品中净生成也变化很大 (12 小时内 17-164 pg g(-1))。这表明微生物群落的变异性和相互作用的复杂性对附生生物中总甲基汞的生成及其对外部刺激的反应非常重要。
