Effects of antibiotics on transformation of nitrate and the associated N₂O release in paddy fields are obscure. Using soil slurry experiments combined with ¹⁵N tracer techniques, the influence of tetracycline and sulfamethazine (applied alone and in combination) on the denitrification, anaerobic ammonium oxidation (anammox), dissimilatory nitrate reduction to ammonium (DNRA) and N₂O release rates in the paddy soil were investigated, while genes related to nitrate reduction and antibiotic resistance were quantified to explore the microbial mechanisms behind the antibiotics’ effects. The potential rates of denitrification, anammox and DNRA were significantly (p < 0.05) reduced, which were mainly attributed to the inhibitory effects of the antibiotics on nitrate-reducing microbes. However, the N₂O release rates were significantly (p < 0.05) stimulated by the antibiotic treatments (0.6–6000 μg kg⁻¹ soil dry weight), which were caused by the different inhibition effects of antibiotics on N₂O production and N₂O reduction as suggest by the changes in abundance of nirS (nitrite reduction step) and nosZ (N₂O reduction to N₂ step) genes. Antibiotic resistance gene (tetA, tetG, sulI and sulIII) abundances were significantly (p < 0.05) increased under high antibiotic exposure concentrations (>600 μg kg⁻¹ soil dry weight). Our results suggest that the widespread occurrence of antibiotics in paddy soils may pose significant eco-environmental risks (nitrate accumulation and greenhouse effects) by altering nitrate transformation processes.

稻田中抗生素对硝酸盐转化和相关的N ₂ O释放的影响是模糊的。利用土壤泥浆实验结合¹⁵ N示踪技术，研究了四环素和磺胺二甲嘧啶（单独应用和组合应用）对反硝化，厌氧铵氧化（厌氧氨氧化），硝化硝酸盐还原为铵态氮（DNRA）和N ₂ O释放速率的影响。对稻田进行了调查，同时定量了与硝酸盐还原和抗生素抗性相关的基因，以探索抗生素作用背后的微生物机制。反硝化，厌氧氨氧化和DNRA的潜在发生率显着（p <0.05）减少，这主要归因于抗生素对减少硝酸盐的微生物的抑制作用。但是， 抗生素处理（0.6–6000μgkg ^-1土壤干重）显着刺激了N ₂ O释放速率（p <0.05），这是由于抗生素对N ₂ O产生和氮的抑制作用不同而引起的。₂ O简化如由丰度的变化表明NIRS（亚硝酸盐还原步骤）和nosZ（N ₂ O简化到N ₂步骤）的基因。抗生素耐药基因（tetA，tetG，sulI和 在高抗生素暴露浓度（> 600μgkg ^-1土壤干重）下，sulIII的丰度显着增加（p <0.05 ）。我们的结果表明，水稻土中抗生素的广泛使用可能会通过改变硝酸盐转化过程而造成重大的生态环境风险（硝酸盐累积和温室效应）。