School of Earth Sciences, University of Melbourne, Parkville, Victoria 3010, Australia.
Wisconsin Water Science Center, US Geological Survey, Middleton, Wisconsin 53562, USA.
Nat Microbiol. 2016 Aug 1;1(10):16127. doi: 10.1038/nmicrobiol.2016.127.
Atmospheric deposition of mercury onto sea ice and circumpolar sea water provides mercury for microbial methylation, and contributes to the bioaccumulation of the potent neurotoxin methylmercury in the marine food web. Little is known about the abiotic and biotic controls on microbial mercury methylation in polar marine systems. However, mercury methylation is known to occur alongside photochemical and microbial mercury reduction and subsequent volatilization. Here, we combine mercury speciation measurements of total and methylated mercury with metagenomic analysis of whole-community microbial DNA from Antarctic snow, brine, sea ice and sea water to elucidate potential microbially mediated mercury methylation and volatilization pathways in polar marine environments. Our results identify the marine microaerophilic bacterium Nitrospina as a potential mercury methylator within sea ice. Anaerobic bacteria known to methylate mercury were notably absent from sea-ice metagenomes. We propose that Antarctic sea ice can harbour a microbial source of methylmercury in the Southern Ocean.
大气中的汞沉降到海冰和环极海水中，为微生物的甲基化作用提供了汞，并导致海洋食物网中具有强烈神经毒性的甲基汞的生物累积。关于极地海洋系统中微生物汞甲基化的非生物和生物控制因素知之甚少。然而，已知汞甲基化与光化学和微生物汞还原以及随后的挥发作用同时发生。在这里，我们将南极雪、盐水、海冰和海水中整个微生物群落 DNA 的宏基因组分析与总汞和甲基汞的汞形态测量相结合，以阐明极地海洋环境中潜在的微生物介导的汞甲基化和挥发途径。我们的研究结果表明，海洋微好氧细菌 Nitrospina 是海冰中潜在的汞甲基化菌。而众所周知的能够使汞甲基化的厌氧细菌在海冰宏基因组中明显缺失。我们提出，南极海冰可以在南大洋中成为甲基汞的微生物来源。
