The abundances of the napA, narG, nirK, nirS, norB, nosZI and nosZII genes, involved in all the steps of the bacterial denitrification pathway, were monitored by a quantitative PCR approach in 4 municipal wastewater treatment plants (WWTPs). The absolute and relative abundances of narG were greater than those of napA in all the surveyed facilities, while few significant differences were found in the case of the nitrite reductase genes nirK and nirS. Greater absolute and relative abundances of the norB gene were always detected in the anoxic bioreactors, and the nosZI gene was more abundant than nosZII in 3 of the WWTPs analysed. Gene abundances were significantly linked to the variations of the operating parameters and environmental conditions influencing the WWTPs, using multivariate analysis. Taken together, the solids retention time (SRT), and the concentrations of nitrite (NO₂⁻) and nitrate (NO₃⁻) in the activated sludge were the major abiotic variables explaining the ordination of samples. These results contribute to understand the shifts of the different groups of denitrifying bacteria in activated sludge, seeking for operation strategies allowing to maximise N removal without increasing nitrous oxide (N₂O) emissions.

通过定量PCR方法在4个市政废水处理厂（WWTP）中监测涉及细菌反硝化途径所有步骤的napA，narG，nirK，nirS，nirS，norB，nosZ I和nosZ II基因的丰度。在所有被调查的设施中，narG的绝对和相对丰度均高于napA，而在亚硝酸还原酶基因nirK和nirS的情况下，几乎没有发现显着差异。norB的绝对和相对丰度更高在缺氧的生物反应器中总是检测到该基因，并且在分析的三个污水处理厂中，nosZ I基因比nosZ II丰富。使用多变量分析，基因丰度与影响污水处理厂的操作参数和环境条件的变化显着相关。两者合计，固体停留时间（SRT），和亚硝酸盐的浓度（NO ₂ ^- ）和硝酸（NO ₃ ^-）是活性污泥中的主要非生物变量，可以解释样品的排序。这些结果有助于了解活性污泥中不同反硝化细菌群的变化，寻求能够最大程度地去除氮而不增加一氧化二氮（N ₂ O）排放的操作策略。