Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing, 100871, China.
Key Laboratory of Water and Sediment Sciences, Ministry of Education, Department of Environmental Engineering, Peking University, Beijing, 100871, China; Collaborative Innovation Center for Advanced Nuclear Energy Technology, INET, Tsinghua University, Beijing, 100084, China.
Environ Pollut. 2021 Dec 15;291:118231. doi: 10.1016/j.envpol.2021.118231. Epub 2021 Sep 24.
Microbial denitrification is a main source of nitrous oxide (NO) emissions which have strong greenhouse effect and destroy stratospheric ozone. Though the importance of sulfide driven chemoautotrophic denitrification has been recognized, its contribution to NO emissions in nature remains elusive. We built up long-term sulfide-added microcosms with sediments from two freshwater lakes. Chemistry analysis confirmed sulfide could drive nitrate respiration in long term. NO accumulated to over 1.5% of nitrate load in both microcosms after long-term sulfide addition, which was up to 12.9 times higher than NO accumulation without sulfide addition. Metagenomes were extracted and sequenced during microcosm incubations. 16 S rRNA genes of Thiobacillus and Defluviimonas were gradually enriched. The nitric oxide reductase with c-type cytochromes as electron donors (cNorB) increased in abundance, while the nitric oxide reductase receiving electrons from quinols (qNorB) decreased in abundance. cnorB genes similar to Thiobacillus were enriched in both microcosms. In parallel, enrichment was observed for enzymes involved in sulfur oxidation, which supplied electrons to nitrate respiration, and enzymes involved in Calvin Cycle, which sustained autotrophic cell growth, implying the coupling relationship between carbon, nitrogen and sulfur cycling processes. Our results suggested sulfur pollution considerably increased NO emissions in natural environments.
微生物反硝化作用是一氧化二氮（N2O）排放的主要来源，它具有很强的温室效应，会破坏平流层臭氧。尽管已经认识到硫化物驱动的化能自养反硝化作用的重要性，但它对自然环境中 N2O 排放的贡献仍不清楚。我们用来自两个淡水湖的沉积物建立了长期添加硫化物的微宇宙。化学分析证实，硫化物可以在长期内驱动硝酸盐呼吸。在长期添加硫化物后，两个微宇宙中的硝酸盐负荷都积累了超过 1.5%的 NO，比没有添加硫化物时的 NO 积累高出 12.9 倍。在微宇宙培养过程中提取并测序了宏基因组。硫杆菌属和脱卤菌属的 16S rRNA 基因逐渐富集。以 c 型细胞色素作为电子供体的一氧化氮还原酶（cNorB）丰度增加，而从醌醇接收电子的一氧化氮还原酶（qNorB）丰度降低。两种微宇宙中都富集了类似于硫杆菌属的 cnorB 基因。同时，还观察到参与硫氧化的酶的富集，这些酶为硝酸盐呼吸提供电子，以及参与卡尔文循环的酶，这些酶维持自养细胞的生长，这意味着碳、氮和硫循环过程之间存在耦合关系。我们的研究结果表明，硫污染会显著增加自然环境中的 NO 排放。
