游离亚硝酸对亚硝酸盐氧化菌活性的抑制作用机制

Inhibitory Mechanism of Free Nitric Acid on Nitrite-Oxidizing Bacteria Activity

为探究游离亚硝酸(FNA)对亚硝酸盐氧化菌(NOB)活性的影响,以富集的NOB菌属为研究对象,基于4种抑制动力学模型,考察了不同pH值(6.5、7.0、8.0)条件下FNA对NOB活性的抑制影响,并基于荧光定量PCR技术,研究了不同pH值条件下,亚硝酸盐氧化还原酶基因(nxrA和nxrB)的变化规律。结果表明:NOB富集系统内硝化杆菌属(Nitrobacter)为最优势菌属,其相对丰度为38.0%;Haldane模型、Aiba模型和Edwards模型均能较好地描述FNA对NOB活性的抑制影响,具有显著的“低促高抑”的特征;统计学分析结果表明Aiba模型最优,获得的最大动力学常数r_(max)为13.63 g N·(g VSS·d)^(-1)(pH值8.0),KS为0.13 mg·L^(-1)(pH值7.0),KI为0.63 mg·L^(-1)(pH值7.0);此外,pH值显著影响nxrA和nxrB基因的绝对丰度,随着pH值的增大,两者均表现出先升高后降低的趋势;nxrA基因的拷贝数(1.6×10^(9)~2.6×10^(9)拷贝数/g湿污泥)比nxrB基因的拷贝数(3.1×10^(7)~4.6×10^(7)拷贝数/g湿污泥)高1~2个数量级,nxrA是NOB菌属的主导功能基因。

In order to explore the effect of free nitric acid(FNA)on nitrite-oxidizing bacteria(NOB)activity,using enriched NOB as research objects,we investigated the inhibition effects of FNA on NOB activity under different pH values(6.5,7.0,and 8.0)based on four inhibition kinetic models.Moreover,we studied the changes of nitrite oxidoreductase genes(nxrA and nxrB)under different pH values by fluorescence quantitative PCR.The results show that Nitrobacter is the most dominant genus in NOB enrichment system,and its relative abundance is 38.0%.The Haldane model,Aiba model,and Edwards model can describe the inhibitory effect of FNA on NOB activity,showing a significant“low promotion and high inhibition”characteristic.The results of statistical analysis show that the Aiba model is the best,and the maximum kinetic constants obtained are r_(max) of 13.63 g N·(g VSS·d)^(-1)(pH value of 8.0),KS of 0.13 mg·L^(-1)(pH value of 7.0),and KI of 0.63 mg·L^(-1)(pH value of 7.0).In addition,pH value can significantly affect the absolute abundance of nxrA and nxrB genes,both of which increase first and then decrease with the increase of pH value.The copy number of nxrA gene(1.6×10^(9)-2.6×10^(9) copy number/g wet sludge)is 1-2 orders of magnitude higher than that of nxrB gene(3.1×10^(7)-4.6×10^(7) copy number/g wet sludge),indicating that nxrA is the dominant functional gene of NOB.