State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China.
Hubei Key Laboratory of Soil Environment and Pollution Remediation, Huazhong Agricultural University, Wuhan 430070, China.
Sci Total Environ. 2020 Apr 20;714:136827. doi: 10.1016/j.scitotenv.2020.136827. Epub 2020 Jan 22.
Methylmercury (MeHg) is a neurotoxin, mainly derived from microbial mercury methylation in natural aquatic environments, and poses threats to human health. Polar regions and paddy soils are potential hotspots of mercury methylation and represent environmental settings that are susceptible to natural and anthropogenic perturbations. The effects of changing environmental conditions on the methylating microorganisms and mercury speciation due to global climate change and farming practices aimed for sustainable agriculture were discussed for polar regions and paddy soils, respectively. To better understand and predict microbial mercury methylation in the changing environment, we synthesized current understanding of how to effectively identify active mercury methylators and assess the bioavailability of different mercury species for methylation. The application of biomarkers based on the hgcAB genes have demonstrated the occurrence of potential mercury methylators, such as sulfate-reducing bacteria, iron-reducing bacteria, methanogen and syntrophs, in a diverse variety of microbial habitats. Advanced techniques, such as enriched stable isotope tracers, whole-cell biosensor and diffusive gradient thin film (DGT) have shown great promises in quantitatively assessing mercury availability to microbial methylators. Improved understanding of the complex structure of microbial communities consisting mercury methylators and non-methylators, chemical speciation of inorganic mercury under geochemically relevant conditions, and the pathway of cellular mercury uptake will undoubtedly facilitate accurate assessment and prediction of in situ microbial mercury methylation.
甲基汞（MeHg）是一种神经毒素，主要来源于自然水生环境中微生物的汞甲基化作用，对人类健康构成威胁。极地地区和稻田土壤是汞甲基化的潜在热点，代表了容易受到自然和人为干扰的环境。分别讨论了全球气候变化和旨在可持续农业的耕作实践对极地地区和稻田土壤中微生物汞甲基化的影响。为了更好地理解和预测变化环境中的微生物汞甲基化作用，我们综合了目前对如何有效识别活性汞甲基化作用者以及评估不同汞物种对甲基化作用的生物可利用性的认识。基于 hgcAB 基因的生物标志物的应用表明，硫酸盐还原菌、铁还原菌、产甲烷菌和共栖菌等潜在的汞甲基化作用者存在于各种微生物生境中。富集稳定同位素示踪剂、全细胞生物传感器和扩散梯度薄膜（DGT）等先进技术已显示出在定量评估微生物甲基化作用者对汞的利用方面具有很大的潜力。深入了解由汞甲基化作用者和非甲基化作用者组成的微生物群落的复杂结构、地球化学相关条件下无机汞的化学形态以及细胞内汞摄取途径，无疑将有助于准确评估和预测原位微生物汞甲基化作用。
