Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, New Jersey 08901, United States.
Environ Sci Technol. 2012 Mar 6;46(5):2684-91. doi: 10.1021/es2033718. Epub 2012 Feb 9.
We investigated microbial methylmercury (CH(3)Hg) production in sediments from the South River (SR), VA, an ecosystem contaminated with industrial mercury (Hg). Potential Hg methylation rates in samples collected at nine sites were low in late spring and significantly higher in late summer. Demethylation of (14)CH(3)Hg was dominated by (14)CH(4) production in spring, but switched to producing mostly (14)CO(2) in the summer. Fine-grained sediments originating from the erosion of river banks had the highest CH(3)Hg concentrations and were potential hot spots for both methylation and demethylation activities. Sequencing of 16S rRNA genes of cDNA recovered from sediment RNA extracts indicated that at least three groups of sulfate-reducing bacteria (SRB) and one group of iron-reducing bacteria (IRB), potential Hg methylators, were active in SR sediments. SRB were confirmed as a methylating guild by amendment experiments showing significant sulfate stimulation and molybdate inhibition of methylation in SR sediments. The addition of low levels of amorphous iron(III) oxyhydroxide significantly stimulated methylation rates, suggesting a role for IRB in CH(3)Hg synthesis. Overall, our studies suggest that coexisting SRB and IRB populations in river sediments contribute to Hg methylation, possibly by temporally and spatially separated processes.
我们研究了弗吉尼亚州南河（SR）沉积物中的微生物甲基汞（CH(3)Hg）的生成，该生态系统受到工业汞（Hg）的污染。在九个地点采集的样本中，春末的潜在汞甲基化率较低，而夏末则显著升高。（14）CH(3)Hg 的去甲基化在春季主要通过（14）CH(4)的生成来主导，但在夏季则主要转化为（14）CO(2)。源自河岸侵蚀的细颗粒沉积物具有最高的 CH(3)Hg 浓度，是甲基化和去甲基化活动的潜在热点。从沉积物 RNA 提取物中回收的 cDNA 的 16S rRNA 基因测序表明，至少有三组硫酸盐还原菌（SRB）和一组铁还原菌（IRB），即潜在的汞甲基化菌，在 SR 沉积物中活跃。硫酸盐还原菌通过添加硫酸盐显著刺激和钼酸盐抑制 SR 沉积物中的甲基化实验被确认为甲基化菌。添加少量无定形三价铁（III）氢氧化物显著刺激了甲基化速率，表明 IRB 在 CH(3)Hg 合成中发挥了作用。总体而言，我们的研究表明，河流沉积物中共存的 SRB 和 IRB 种群可能通过时间和空间上分离的过程促进 Hg 甲基化。
