Institute of Agriculture and Life Sciences, Gyeongsang National University, Jinju, 660-701, South Korea.
Division of Applied Life Science, Gyeongsang National University, Jinju, 660-701, South Korea.
Environ Res. 2024 Dec 15;263(Pt 3):120257. doi: 10.1016/j.envres.2024.120257. Epub 2024 Oct 29.
Methanogens play an important role in the demethylation of arsenic. Soil amendments that inhibit methanogens can increase dimethylarsinic acid (DMA), which is responsible for straighthead disease in rice. A decrease in methanogenesis caused by silicate fertilizer may increase DMA concentration in paddy soils and rice grains; the relationship between these two factors and their impacts on DMA concentration remains unclear. We applied silicate fertilizer (2 Mg ha) to japonica and indica rice grown on arsenic-spiked soils and found a simultaneous reduction in methane emissions and pore-water DMA concentration, compared to no-silicate fertilization. Gene and transcript copies of mcrA and arsM, as well as dominant methanogens and arsenic-methylating microbes decreased significantly with silicate fertilization. However, the sulfate-reducing bacteria and the gene and transcript copies of dsrB did not change significantly in response to the application of silicate fertilizer to paddy soils. The abundance of arsenic methylating microbes was significantly and positively correlated with the abundance of methanogens, but not with the abundance of sulfate-reducing bacteria. Methylomonas and Methylobacter, which harbor the arsM gene, were suppressed under silicate fertilization, suggesting that they have the potential to methylate As and play a crucial role in reducing pore-water DMA in As-enriched flooded paddy soils. Increasing Fe concentration, soil pH, and Eh value decreased pore-water DMA concentration, while decreasing arsenite concentration, arsM and mcrA gene abundance decreased it. While silicate fertilization decreased arsenite and DMA concentrations in pore-water, it had no significant effect on rice DMA content, but significantly decreased arsenite content. Results reveal that methanogens and arsenic-methylating microbes have a synergistic relationship under silicate fertilization that facilitates a significant reduction in methane emissions and DMA concentration in As-enriched paddy soils.
产甲烷菌在砷的去甲基化过程中发挥着重要作用。抑制产甲烷菌的土壤改良剂会增加二甲砷酸（DMA）的含量，而 DMA 正是导致水稻直头病的原因。硅酸盐肥料引起的产甲烷作用减少可能会增加稻田土壤和水稻籽粒中 DMA 的浓度；这两个因素之间的关系及其对 DMA 浓度的影响尚不清楚。我们在砷污染土壤上种植的粳稻和籼稻中施加了硅酸盐肥料（2 Mg/ha），结果发现与不施加硅酸盐肥料相比，甲烷排放量和孔隙水 DMA 浓度同时降低。施加硅酸盐肥料后，mcrA 和 arsM 的基因和转录本拷贝以及优势产甲烷菌和砷甲基化微生物显著减少。然而，硫酸盐还原菌以及 dsrB 的基因和转录本拷贝对硅酸盐肥料在稻田中的应用没有明显变化。砷甲基化微生物的丰度与产甲烷菌的丰度显著正相关，但与硫酸盐还原菌的丰度无关。含有 arsM 基因的甲基单胞菌属和甲基杆菌属在硅酸盐施肥条件下受到抑制，这表明它们有潜力将砷甲基化，并在减少富砷淹没稻田中孔隙水 DMA 方面发挥关键作用。增加铁浓度、土壤 pH 值和 Eh 值会降低孔隙水 DMA 浓度，而降低亚砷酸盐浓度、arsM 和 mcrA 基因丰度会降低孔隙水 DMA 浓度。硅酸盐施肥虽然降低了孔隙水中的亚砷酸盐和 DMA 浓度，但对水稻 DMA 含量没有显著影响，但显著降低了亚砷酸盐含量。结果表明，在硅酸盐施肥条件下，产甲烷菌和砷甲基化微生物具有协同关系，可显著减少富砷稻田中的甲烷排放和 DMA 浓度。
