Moreau John W, Gionfriddo Caitlin M, Krabbenhoft David P, Ogorek Jacob M, DeWild John F, Aiken George R, Roden Eric E
School of Earth Sciences, University of Melbourne Melbourne, VIC, Australia.
United States Geological Survey Middleton, WI, USA.
Front Microbiol. 2015 Dec 18;6:1389. doi: 10.3389/fmicb.2015.01389. eCollection 2015.
Methylation of tracer and ambient mercury ((200)Hg and (202)Hg, respectively) equilibrated with four different natural organic matter (NOM) isolates was investigated in vivo using the Hg-methylating sulfate-reducing bacterium Desulfobulbus propionicus 1pr3. Desulfobulbus cultures grown fermentatively with environmentally representative concentrations of dissolved NOM isolates, Hg[II], and HS(-) were assayed for absolute methylmercury (MeHg) concentration and conversion of Hg(II) to MeHg relative to total unfiltered Hg(II). Results showed the (200)Hg tracer was methylated more efficiently in the presence of hydrophobic NOM isolates than in the presence of transphilic NOM, or in the absence of NOM. Different NOM isolates were associated with variable methylation efficiencies for either the (202)Hg tracer or ambient (200)Hg. One hydrophobic NOM, F1 HpoA derived from dissolved organic matter from the Florida Everglades, was equilibrated for different times with Hg tracer, which resulted in different methylation rates. A 5 day equilibration with F1 HpoA resulted in more MeHg production than either the 4 h or 30 day equilibration periods, suggesting a time dependence for NOM-enhanced Hg bioavailability for methylation.
使用汞甲基化硫酸盐还原菌丙酸脱硫球菌1pr3在体内研究了与四种不同天然有机物（NOM）分离物平衡的示踪汞和环境汞（分别为²⁰⁰Hg和²⁰²Hg）的甲基化情况。用具有环境代表性浓度的溶解NOM分离物、Hg[II]和HS⁻进行发酵培养的丙酸脱硫球菌培养物，测定了绝对甲基汞（MeHg）浓度以及相对于总未过滤Hg(II)而言Hg(II)向MeHg的转化情况。结果表明，与亲水性NOM存在时相比，在疏水性NOM分离物存在下，²⁰⁰Hg示踪剂的甲基化效率更高，或者在不存在NOM时也是如此。不同的NOM分离物与²⁰²Hg示踪剂或环境²⁰⁰Hg的甲基化效率变化相关。一种疏水性NOM，即源自佛罗里达大沼泽地溶解有机物的F1 HpoA，与Hg示踪剂平衡不同时间，这导致了不同的甲基化速率。与F1 HpoA平衡5天产生的MeHg比4小时或30天平衡期更多，这表明NOM提高汞生物可利用性以进行甲基化存在时间依赖性。
