Department of Ecology and Genetics, Limnology, Uppsala University, Uppsala, Sweden.
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Sci Rep. 2019 Jan 24;9(1):518. doi: 10.1038/s41598-018-37383-z.
The formation of the potent neurotoxic methylmercury (MeHg) is a microbially mediated process that has raised much concern because MeHg poses threats to wildlife and human health. Since boreal forest soils can be a source of MeHg in aquatic networks, it is crucial to understand the biogeochemical processes involved in the formation of this pollutant. High-throughput sequencing of 16S rRNA and the mercury methyltransferase, hgcA, combined with geochemical characterisation of soils, were used to determine the microbial populations contributing to MeHg formation in forest soils across Sweden. The hgcA sequences obtained were distributed among diverse clades, including Proteobacteria, Firmicutes, and Methanomicrobia, with Deltaproteobacteria, particularly Geobacteraceae, dominating the libraries across all soils examined. Our results also suggest that MeHg formation is also linked to the composition of non-mercury methylating bacterial communities, likely providing growth substrate (e.g. acetate) for the hgcA-carrying microorganisms responsible for the actual methylation process. While previous research focused on mercury methylating microbial communities of wetlands, this study provides some first insights into the diversity of mercury methylating microorganisms in boreal forest soils.
强神经毒性的甲基汞（MeHg）的形成是一个微生物介导的过程，引起了广泛关注，因为 MeHg 对野生动植物和人类健康构成威胁。由于北方森林土壤可能是水生网络中 MeHg 的来源，因此了解形成这种污染物的生物地球化学过程至关重要。使用 16S rRNA 和汞甲基转移酶 hgcA 的高通量测序，并结合土壤地球化学特征，确定了在瑞典各地森林土壤中形成 MeHg 的微生物种群。获得的 hgcA 序列分布在多个进化枝中，包括变形菌门、厚壁菌门和甲烷微菌门，其中δ变形菌门，特别是地杆菌科，在所有检查的土壤文库中占主导地位。我们的研究结果还表明，MeHg 的形成也与非汞甲基化细菌群落的组成有关，可能为负责实际甲基化过程的携带 hgcA 的微生物提供生长基质（例如乙酸盐）。虽然以前的研究集中于湿地中汞甲基化微生物群落，但本研究首次深入了解了北方森林土壤中汞甲基化微生物的多样性。
