Composting is widely used for organic waste management and is also a major source of nitrous oxide (N₂O) emission. New insight into microbial sources and sinks is essential for process regulation to reduce N₂O emission from composting. This study used genome-resolved metagenomics to decipher the genomic structures and physiological behaviors of individual bacteria for N₂O sources and sinks during composting. Results showed that several nosZ-lacking denitrifiers in feedstocks drove N₂O emission at the beginning of the composting. Such emission became negligible at the thermophilic stage, as high temperatures inhibited all denitrifiers for N₂O production except for those containing nirK. The nosZ-lacking denitrifiers were notably enriched to increase N₂O production at the cooling stage. Nevertheless, organic biodegradation limited energy availability for chemotaxis and flagellar assembly to restrain nirKS-containing denitrifiers for nitrate reduction toward N₂O sources but insignificantly interrupt norBC- and nosZ-containing bacteria (particularly nosZ-containing nondenitrifiers) for N₂O sinks by capturing N₂O and nitric oxide (NO) for energy production, thereby reducing N₂O emission at the mature stage. Furthermore, nosZII-type bacteria included all nosZ-containing nondenitrifiers and dominated N₂O sinks. Thus, targeted strategies can be developed to restrict the physiological behaviors of nirKS-containing denitrifiers and expand the taxonomic distribution of nosZ for effective N₂O mitigation in composting.

中文翻译：

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有机垃圾堆肥过程中一氧化二氮的微生物源和汇

堆肥广泛用于有机废物管理，也是一氧化二氮（N ₂ O）排放的主要来源。对微生物源和汇的新见解对于减少堆肥中 N ₂ O 排放的过程调节至关重要。这项研究使用基因组解析的宏基因组学来破译堆肥过程中 N ₂ O 源和汇的单个细菌的基因组结构和生理行为。结果表明，原料中几种缺乏nosZ的反硝化菌在堆肥开始时促进了N ₂ O的排放。这种排放在高温阶段变得可以忽略不计，因为除了那些含有nirK的反硝化菌之外，高温抑制了所有 N ₂ O 反硝化菌的产生。缺乏nosZ的反硝化菌显着富集，以增加冷却阶段的N ₂ O产量。然而，有机生物降解限制了趋化性和鞭毛组装的能量可用性，以抑制含nirKS的反硝化菌将硝酸盐还原为 N ₂ O 源，但通过捕获而微不足道地中断了含NorBC和nosZ的细菌（特别是含nosZ的非反硝化菌）的 N ₂ O 汇。 N ₂ O和一氧化氮（NO）用于能源生产，从而减少成熟阶段的N ₂ O排放。此外，nosZII型细菌包括所有含nosZ的非反硝化菌并占主导地位的N ₂ O汇。因此，可以制定有针对性的策略来限制含有nirKS的反硝化菌的生理行为，并扩大nosZ的分类分布，以有效减少堆肥中的 N ₂ O。