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Active microbial arsenic methylation in saline-alkaline paddy soil
Jing Liu1, Li Ye1, Chuanyong Jing2
1Shandong Key Laboratory of Environmental Processes and Health, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China.
The Science of the Total Environment
|December 26, 2022
Summary
Seawater rice cultivation faces arsenic risks. Soil microbes transform arsenic (As) into methylated forms, preventing its uptake by rice grains, ensuring food safety.
Area of Science:
- Environmental Science
- Microbiology
- Agricultural Science
Background:
- Seawater rice is crucial for food security in coastal areas.
- Salt-tolerant rice may accumulate arsenic (As) in saline-alkaline soils.
- Understanding As mobility and transformation in these environments is vital.
Purpose of the Study:
- To investigate the mobility and transformation of arsenic in saline-alkaline paddy soil.
- To identify the microbial mechanisms driving arsenic methylation.
- To assess the risk of arsenic accumulation in rice grains.
Main Methods:
- Incubation of saline-alkaline paddy soil with river water for three months.
- Analysis of arsenic species (As(V), As(III), DMA) in soil and porewater.
- Quantification of arsenic-related genes, particularly arsenite methyltransferase (arsM).
- Microbial community analysis using 16S rRNA gene sequencing (OTUs).
Main Results:
- Solid-bound arsenic (As(V)) reduced to As(III) within two weeks, releasing into porewater.
- Dissolved As(III) was methylated to dimethyl arsenate (DMA), dominating porewater (87-100%).
- High abundance of the arsenite methyltransferase gene (arsM) correlated with elevated methylation.
- Salt-tolerant bacteria, Chloroflexi and Actinobacteria, were identified as potential drivers of As methylation.
Conclusions:
- Microbial arsenic methylation in saline-alkaline soils effectively immobilizes arsenic.
- Dominance of methylated arsenic in porewater did not lead to increased accumulation in rice grains.
- Seawater rice cultivation remains a safe option regarding arsenic contamination.
