硫酸盐还原菌和产甲烷古菌参与水稻土壤中砷的甲基化和脱甲基作用

来源：土壤观察

原标题：The ISME Journal：硫酸盐还原菌和产甲烷古菌参与水稻土壤中砷的甲基化和脱甲基作用|研究...

导  读

南京农业大学赵方杰教授团队成果。

来源：农业环境科学公号（2019年8月11日）

南京农业大学资源与环境学院赵方杰教授团队研究了淹水条件下三种水稻土中的DMAs的动态变化及参与该变化过程的微生物功能群。相关结果发表于The ISME Journal（IF=9.493）。

Abstract

Microbial arsenic (As) methylation and demethylation are important components of the As biogeochemical cycle. Arsenic methylation is enhanced under flooded conditions in paddy soils, producing mainly phytotoxic dimethylarsenate (DMAs) that can cause rice straighthead disease, a physiological disorder occurring widely in some rice growing regions. The key microbial groups responsible for As methylation and demethylation in paddy soils are unknown. Three paddy soils were incubated under flooded conditions. DMAs initially accumulated in the soil porewater, followed by a rapid disappearance coinciding with the production of methane. The soil from a rice straighthead disease paddy field produced a much larger amount of DMAs than the other two soils. Using metabolic inhibition, quantification of functional gene transcripts, microbial enrichment cultures and 13C-labeled DMAs, we show that sulfate-reducing bacteria (SRB) and methanogenic archaea are involved in As methylation and demethylation, respectively, controlling the dynamics of DMAs in paddy soils. We present a model of As biogeochemical cycle in paddy soils, linking the dynamics of changing soil redox potential with arsenite mobilization, arsenite methylation and subsequent demethylation driven by different microbial groups. The model provides a basis for controlling DMAs accumulation and incidence of straighthead disease in rice. 

微生物砷的甲基化和去甲基化是砷元素生物地球化学循环的重要组成部分。在淹水条件下，水稻土壤中砷的甲基化作用增强，主要产物为具有植物毒性的二甲基砷酸盐（DMAs），可引起一种在某些水稻生长区广泛发生的疾病——水稻直头病。水稻土中主导砷甲基化和去甲基化的主要微生物功能群尚不清楚。本研究在淹水条件下培育了三种水稻土。DMAs最初聚集在土壤孔隙水中，随后迅速消失并产生甲烷。水稻直头病稻田的土壤比其他两种土壤产生的DMAs量大得多。利用代谢抑制、功能基因转录物定量分析、微生物富集培养和13C标记DMAs，研究发现硫酸盐还原菌（SRB）和产甲烷古菌分别参与甲基化和去甲基化过程，控制了水稻土中的DMAs动态。

本文提出了稻田土壤中砷的生物地球化学循环模型，将土壤氧化还原电位的变化与砷的迁移、亚砷酸盐甲基化以及不同微生物功能群驱动的后续去甲基化作用联系起来。该模型为控制水稻直头病的发生和抑制土壤中DMAs积累提供了依据。