稻田土壤微生物甲烷氧化代谢产物对汞甲基化的影响
- The Effect of Microbial Methane Oxidation Metabolites in Paddy Soils on Mercury Methylation
- 摘要：稻田生态系统中厌氧微生物可以将无机汞(Hg)转化成毒性更强的甲基汞(MeHg)。稻米可以从土壤中富集 MeHg,从而威胁人类健康。土壤微生物也能将稻田系统中的甲烷(CH4)氧化,产生代谢产物会影响稻田土壤中的其它氧化还原过程。然而,稻田 CH4 氧化产生的中间代谢产物如何影响微生物对 Hg 的甲基化仍不清楚。本研究选取黑龙江海伦、湖南岳阳和广东广州三种典型稻田土壤,通过微宇宙培养实验并结合代谢组分析,探究了 CH4 氧化代谢产物对土壤 Hg甲基化的影响。结果表明,添加 CH4 氧化代谢产物均促进了三种稻田土壤中 MeHg 的生成,MeHg 浓度分别增加了 2.69、3.94 和 8.16 倍。在单菌培养下,CH4 氧化代谢产物显著促进了 Hg 甲基化微生物 Geobacter sulfurreducens PCA 对 Hg 的甲基化效率,Hg 甲基化率(%MeHg)从 8.00% 增加至 18.16%。代谢组学分析表明,培养 24 小时后,有 98 个 CH4 氧化代谢产物与 G. sulfurreducens PCA 生成 MeHg 有关。此外,KEGG 化合物分类与变量重要性投影分析结果表明,苹果酸、富马酸和丁酸是促进 Hg 甲基化效率的关键代谢产物。这些结果阐明了稻田土壤 CH4 氧化代谢产物对 Hg 甲基化影响途径,为揭示稻田土壤 MeHg 的积累机制提供理论依据。
- Abstract：Anaerobic microbes in paddy field ecosystems can convert inorganic mercury (Hg) into the more toxic methylmercury (MeHg). Rice plants accumulate MeHg from soils, thereby rice ingestion threatening human health. At the same time, microbes can also oxidize methane (CH4) and produce metabolites that influence other redox processes in paddy soils. However, how the metabolites from CH? oxidation affect Hg methylation in paddy soils and the underlying mechanisms remain unclear. Here we selected three typical rice soils from Heilongjiang Hailun, Hunan Yueyang and Guangdong Guangzhou respectively to investigate the effects of CH4 oxidative metabolites on Hg methylation in paddy soils through microcosm incubation experiments and metabolomic analysis. Results showed that the addition of methanotrophic metabolites promoted the MeHg production in all the three paddy soils, with MeHg concentrations increasing by 2.69, 3.94, and 8.16 folds, respectively. Metabolites from CH? oxidation significantly enhanced the MeHg production by Hg methylator Geobacter sulfurreducens PCA, increasing the Hg methylation rate from 8.00% to 18.16%. Metabolomics analysis showed that 98 metabolites from CH? oxidation were related to the MeHg production by G. sulfurreducens PCA after 24 hours incubation. In addition, KEGG compound classification and variable importance projection analyses identified malic acid, fumaric acid, and butyric acid as key metabolites that related to promoting the MeHg production. These findings elucidate the effects of metabolites from CH? oxidation on Hg methylation and provide a theoretical foundation for revealing the mechanisms of MeHg accumulation in paddy soils.
