The active denitrifying communities performing methane oxidation coupled to denitrification (MOD) were investigated using samples from an aerobic reactor (∼20% O and 2% CH) and a microaerobic reactor (2% O, 2% CH) undertaking denitrification. The methane oxidation metabolites excreted in the reactors were acetate, methanol, formate and acetaldehyde. Using anaerobic batch experiments supplemented with exogenously supplied C-labelled metabolites, the active denitrifying bacteria were identified using 16S rRNA amplicon sequencing and RNA-stable isotope probing (RNA-SIP). With the aerobic reactor (AR) samples, the maximum NO removal rates were 0.43 mmol g d, 0.40 mmol g d, 0.33 mmol g d and 0.10 mmol g d for exogenously supplied acetate, formate, acetaldehyde and methanol batch treatments respectively, while with the microaerobic reactor (MR) samples, the maximum NO removal rates were 0.41 mmol g d, 0.33 mmol g d, 0.38 mmol g d and 0.14 mmol g d for exogenously supplied acetate, formate, acetaldehyde and methanol batch treatments respectively. The RNA-SIP experiments with C-labelled acetate, formate, and methanol identified , and as the active methane-driven denitrifying bacteria in the AR samples, while and were the active MOD bacteria in the MR samples. Collectively, all the data indicate that formate is a key cross-feeding metabolite excreted by methanotrophs and consumed by denitrifiers performing MOD.

中文翻译：

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使用 RNA 稳定同位素探测研究甲烷氧化代谢物和甲烷氧化与反硝化耦合中的活性微生物群落

使用来自进行反硝化的好氧反应器（〜20％O和2％CH）和微氧反应器（2％O，2％CH）的样品对执行甲烷氧化耦合反硝化（MOD）的活性反硝化群落进行了研究。反应器中排出的甲烷氧化代谢物为乙酸盐、甲醇、甲酸盐和乙醛。通过厌氧批量实验并辅以外源 C 标记代谢物，利用 16S rRNA 扩增子测序和 RNA 稳定同位素探测 (RNA-SIP) 鉴定了活性反硝化细菌。对于好氧反应器 (AR) 样品，对于外源供应的乙酸盐、甲酸盐、乙醛和甲醇批量处理，最大 NO 去除率分别为 0.43 mmol gd、0.40 mmol gd、0.33 mmol gd 和 0.10 mmol gd，而使用微氧反应器（ MR）样品中，对于外源提供的乙酸盐、甲酸盐、乙醛和甲醇批次处理，最大NO去除率分别为0.41 mmol gd、0.33 mmol gd、0.38 mmol gd和0.14 mmol gd。使用 C 标记的乙酸盐、甲酸盐和甲醇进行的 RNA-SIP 实验确定 和 是 A​​R 样品中的活性甲烷驱动反硝化细菌，而 和 是 MR 样品中的活性 MOD 细菌。总的来说，所有数据表明，甲酸是一种关键的交叉喂养代谢物，由甲烷氧化菌分泌，并被执行 MOD 的反硝化菌消耗。