Nitrite-dependent anaerobic methane oxidation (n-damo) catalyzed by Candidatus Methylomirabilis oxyfera (M. oxyfera)-like bacteria is a new pathway for the regulation of methane emissions from paddy fields. Elevated atmospheric CO₂ concentrations (e[CO₂]) can indirectly affect the structure and function of microbial communities. However, the response of M. oxyfera-like bacteria to e[CO₂] is currently unknown. Here, we investigated the effect of e[CO₂] (ambient CO₂ + 200 ppm) on community composition, abundance, and activity of M. oxyfera-like bacteria at different depths (0–5, 5–10, and 10–20 cm) in paddy fields across multiple rice growth stages (tillering, jointing, and flowering). High-throughput sequencing showed that e[CO₂] had no significant effect on the community composition of M. oxyfera-like bacteria. However, quantitative PCR suggested that the 16S rRNA gene abundance of M. oxyfera-like bacteria increased significantly in soil under e[CO₂], particularly at the tillering stage. Furthermore, ¹³CH₄ tracer experiments showed potential n-damo activity of 0.31–8.91 nmol CO₂ g⁻¹ (dry soil) d⁻¹. E[CO₂] significantly stimulated n-damo activity, especially at the jointing and flowering stages. The n-damo activity and abundance of M. oxyfera-like bacteria increased by an average of 90.9% and 50.0%, respectively, under e[CO₂]. Correlation analysis showed that the increase in soil dissolved organic carbon content caused by e[CO₂] had significant effects on the activity and abundance of M. oxyfera-like bacteria. Overall, this study provides the first evidence for a positive response of M. oxyfera-like bacteria to e[CO₂], which may help reduce methane emissions from paddy fields under future climate change conditions.

由Candidatus Methylomirabilis oxyfera ( M. oxyfera ) 样细菌催化的亚硝酸盐依赖性厌氧甲烷氧化(n-damo)是调节稻田甲烷排放的新途径。升高的大气 CO ₂浓度 (e[CO ₂ ]) 可以间接影响微生物群落的结构和功能。然而，M. oxyfera样细菌对 e[CO ₂ ] 的反应目前尚不清楚。在这里，我们研究了 e[CO ₂ ]（环境 CO ₂  + 200 ppm）对M. oxyfera群落组成、丰度和活性的影响稻田中不同深度（0-5、5-10 和 10-20 厘米）的类细菌，跨越多个水稻生长阶段（分蘖、拔节和开花）。高通量测序表明e[CO ₂ ]对M. oxyfera样细菌群落组成没有显着影响。然而，定量PCR表明，在e[CO ₂ ]下土壤中，M. oxyfera样细菌的16S rRNA基因丰度显着增加，特别是在分蘖阶段。此外，¹³ CH ₄示踪剂实验显示潜在的 n-damo 活性为 0.31–8.91 nmol CO ₂ g ^-1（干土）d ^-1。E[CO ₂] 显着刺激了 n-damo 活性，尤其是在拔节和开花阶段。在e[CO ₂ ]条件下，M. oxyfera样细菌的n-damo 活性和丰度分别平均增加了90.9% 和50.0% 。相关性分析表明，e[CO ₂ ]引起的土壤溶解有机碳含量的增加对M. oxyfera样细菌的活性和丰度有显着影响。总体而言，这项研究为M. oxyfera样细菌对 e[CO ₂ ]的积极响应提供了第一个证据，这可能有助于在未来的气候变化条件下减少稻田的甲烷排放。