Contrasting Effects of Dissolved Organic Matter on Mercury Methylation by Geobacter sulfurreducens PCA and Desulfovibrio desulfuricans ND132,Environmental Science & Technology

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Contrasting Effects of Dissolved Organic Matter on Mercury Methylation by Geobacter sulfurreducens PCA and Desulfovibrio desulfuricans ND132
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2017-08-29 00:00:00 , DOI: 10.1021/acs.est.7b02518
Linduo Zhao ₁ , Hongmei Chen ₁ , Xia Lu ₁ , Hui Lin ₁ , Geoff A. Christensen ₂ , Eric M. Pierce ₁ , Baohua Gu ₁

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Natural dissolved organic matter (DOM) affects mercury (Hg) redox reactions and anaerobic microbial methylation in the environment. Several studies have shown that DOM can enhance Hg methylation, especially under sulfidic conditions, whereas others show that DOM inhibits Hg methylation due to strong Hg–DOM complexation. In this study, we investigated and compared the effects of DOM on Hg methylation by an iron-reducing bacterium Geobacter sulfurreducens PCA and a sulfate-reducing bacterium Desulfovibrio desulfuricans ND132 under nonsulfidic conditions. The methylation experiment was performed with washed cells either in the absence or presence of DOM or glutathione, both of which form strong complexes with Hg via thiol-functional groups. DOM was found to greatly inhibit Hg methylation by G. Sulfurreducens PCA but enhance Hg methylation by D. desulfuricans ND132 cells with increasing DOM concentration. These strain-dependent opposing effects of DOM were also observed with glutathione, suggesting that thiols in DOM likely played an essential role in affecting microbial Hg uptake and methylation. Additionally, DOM and glutathione greatly decreased Hg sorption by G. sulfurreducens PCA but showed little effect on D. desulfuricans ND132 cells, demonstrating that ND132 has a higher affinity to sorb or take up Hg than the PCA strain. These observations indicate that DOM effects on Hg methylation are bacterial strain specific, depend on the DOM:Hg ratio or site-specific conditions, and may thus offer new insights into the role of DOM in methylmercury production in the environment.

中文翻译：

溶解性有机物对土壤杆菌还原性PCA和脱硫脱硫弧菌ND132甲基化汞甲基化的影响

天然溶解的有机物（DOM）影响环境中的汞（Hg）氧化还原反应和厌氧微生物甲基化。一些研究表明，DOM可以增强Hg甲基化，特别是在硫化条件下，而另一些研究则表明，由于Hg-DOM的强络合作用，DOM可以抑制Hg甲基化。在这项研究中，我们调查和比较了DOM对铁还原细菌Geobacter sulphreducens PCA和硫酸盐还原细菌Desulfovibrio desulfuricans对汞甲基化的影响。ND132在非硫化条件下。在不存在或存在DOM或谷胱甘肽的情况下，用洗涤过的细胞进行甲基化实验，两者均通过硫醇官能团与Hg形成强络合物。DOM被发现极大地抑制汞的甲基化G.硫还原PCA而是增强汞的甲基化由D.弧菌ND132细胞随着DOM的浓度。在谷胱甘肽中也观察到了DOM的这些依赖菌株的相反作用，这表明DOM中的硫醇可能在影响微生物吸收汞和甲基化方面起着至关重要的作用。此外，DOM和谷胱甘肽大大降低了G. sulphurensens PCA对Hg的吸附，但对D. desulfuricans几乎没有影响ND132细胞，表明ND132与PCA株相比具有更高的吸附或吸收Hg亲和力。这些观察结果表明DOM对Hg甲基化的影响是细菌菌株特异的，取决于DOM：Hg比率或特定位置的条件，因此可能为DOM在环境中甲基汞生产中的作用提供新的见解。

更新日期：2017-08-30

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