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Mercury methylation by metabolically versatile and cosmopolitan marine bacteria
The ISME Journal ( IF 11.0 ) Pub Date : 2021-01-27 , DOI: 10.1038/s41396-020-00889-4
Heyu Lin 1 , David B Ascher 2, 3 , Yoochan Myung 2, 3 , Carl H Lamborg 4 , Steven J Hallam 5, 6 , Caitlin M Gionfriddo 7, 8 , Kathryn E Holt 9, 10 , John W Moreau 1, 11
Affiliation  

Microbes transform aqueous mercury (Hg) into methylmercury (MeHg), a potent neurotoxin that accumulates in terrestrial and marine food webs, with potential impacts on human health. This process requires the gene pair hgcAB, which encodes for proteins that actuate Hg methylation, and has been well described for anoxic environments. However, recent studies report potential MeHg formation in suboxic seawater, although the microorganisms involved remain poorly understood. In this study, we conducted large-scale multi-omic analyses to search for putative microbial Hg methylators along defined redox gradients in Saanich Inlet, British Columbia, a model natural ecosystem with previously measured Hg and MeHg concentration profiles. Analysis of gene expression profiles along the redoxcline identified several putative Hg methylating microbial groups, including Calditrichaeota, SAR324 and Marinimicrobia, with the last the most active based on hgc transcription levels. Marinimicrobia hgc genes were identified from multiple publicly available marine metagenomes, consistent with a potential key role in marine Hg methylation. Computational homology modelling predicts that Marinimicrobia HgcAB proteins contain the highly conserved amino acid sites and folding structures required for functional Hg methylation. Furthermore, a number of terminal oxidases from aerobic respiratory chains were associated with several putative novel Hg methylators. Our findings thus reveal potential novel marine Hg-methylating microorganisms with a greater oxygen tolerance and broader habitat range than previously recognized.



中文翻译:

代谢多才多艺的海洋细菌对汞的甲基化

微生物将含水汞 (Hg) 转化为甲基汞 (MeHg),这是一种在陆地和海洋食物网中积累的强效神经毒素,对人类健康具有潜在影响。这个过程需要基因对hgcAB, 它编码驱动 Hg 甲基化的蛋白质,并且已经很好地描述了缺氧环境。然而,最近的研究报告了在低氧海水中可能形成甲基汞,尽管对所涉及的微生物仍然知之甚少。在这项研究中,我们进行了大规模的多组学分析,以在不列颠哥伦比亚省 Saanich Inlet 中沿着定义的氧化还原梯度寻找假定的微生物 Hg 甲基化物,Saanich Inlet 是一个具有先前测量的 Hg 和 MeHg 浓度分布的模型自然生态系统。沿氧化还原素的基因表达谱分析确定了几个假定的 Hg 甲基化微生物组,包括 Calditrichaeota、SAR324 和 Marinimicrobia,最后一个基于 hgc 转录水平最活跃海洋微生物hgc从多个公开可用的海洋宏基因组中鉴定出基因,这与海洋 Hg 甲基化中的潜在关键作用一致。计算同源性建模预测 Marinimicrobia HgcAB 蛋白包含功能性 Hg 甲基化所需的高度保守的氨基酸位点和折叠结构。此外,有氧呼吸链中的许多末端氧化酶与几种推定的新型 Hg 甲基化酶有关。因此,我们的研究结果揭示了潜在的新型海洋汞甲基化微生物,它们具有比以前认识到的更高的耐氧性和更广泛的栖息地范围。

更新日期:2021-01-27
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