Enterobacter cloacae strain HNR was found to grow well and denitrify aerobically at high NO3−—N concentrations. When the concentrations of NO3-—N were 200, 300 and 500 mg/L, the removal efficiencies of NO3-—N were 83%, 74.5% and 75%, respectively. More importantly, the intermediates accumulation of NO2-—N and NH4+—N was not obvious during the aerobic denitrification processes, resulting in a high TN removal of 82%, 74% and 70%, respectively. Meanwhile, strain HNR also presented the ability of heterotrophic nitrification. With initial NH4+—N concentrations of 20 and 80 mg/L, the NH4+—N removal efficiency reached 78% and 76%, respectively. The key nitrate reductase enzyme gene relating to denitrification was successfully amplified by polymerase chain reaction (PCR) from strain HNR, and identified it as napA, which encodings the large catalytic subunit A of periplasmic nitrate reductase (NAPA). The sequence analysis of napA indicates that NAPA is a hydrophilic, non-transmembrane protein. The existence of napA might be crucial for strain HNR to denitrify nitrate under aerobic conditions. This study showed prospect to develop novel technology for nitrogen removal by application of E. cloacae strain HNR.

中文翻译：

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一株好氧反硝化菌阴沟肠杆菌HNR及其硝酸还原酶基因的表征

发现阴沟肠杆菌菌株 HNR 在高 NO3--N 浓度下生长良好并在有氧条件下脱氮。当NO3--N的浓度为200、300和500 mg/L时，NO3--N的去除效率分别为83%、74.5%和75%。更重要的是，在好氧反硝化过程中，NO2--N和NH4+-N的中间体积累并不明显，导致TN去除率分别高达82%、74%和70%。同时，菌株HNR也表现出异养硝化能力。当初始 NH4+-N 浓度为 20 和 80 mg/L 时，NH4+-N 去除效率分别达到 78% 和 76%。通过聚合酶链反应（PCR）从HNR菌株中成功扩增出与反硝化作用相关的关键硝酸还原酶基因，并鉴定为napa，它编码周质硝酸还原酶 (NAPA) 的大催化亚基 A。NAPA 的序列分析表明，NAPA 是一种亲水性、非跨膜蛋白。NAPA 的存在可能对 HNR 菌株在有氧条件下反硝化硝酸盐至关重要。本研究为开发应用阴沟肠杆菌HNR脱氮新技术提供了前景。