稻田厌氧氨氧化菌群落结构对氮肥的响应

为探明稻田厌氧氨氧化菌多样性及其对氮肥用量的响应状况,利用厌氧氨氧化菌16S rRNA基因特异引物对定位试验稻田土壤DNA进行PCR-DGGE(聚合酶链反应变性梯度凝胶电泳)并结合DNA克隆测序,研究了氮肥供应量对厌氧氨氧化菌群落结构的影响。DGGE图谱及依据其条带位置和亮度数值计算的多样性指数均显示:高氮处理N3:225 kg(N).hm 2]的厌氧氨氧化菌群落结构多样性在表层或根层土壤中均显著(P<0.05)高于中、低氮N2:150 kg(N).hm 2;N1:75 kg(N).hm 2]处理和不施肥对照(CK);同时,高氮处理下表层土壤厌氧氨氧化菌群落多样性指数显著高于根层土壤(P<0.05)。冗余分析(RDA)结果表明,表层土壤中厌氧氨氧化菌群落结构组成与不同氮肥水平处理存在显著相关性(P=0.006)。此外,本试验获得厌氧氨氧化菌DGGE条带DNA序列18条,登录GenBank并获得登录号。研究表明稻田厌氧氨氧化菌群落结构对高氮水平具有较强的响应,尤其是在表层土壤中。

Response of anammox bacteria community structure to nitrogen in paddy soils

Anaerobic ammonium oxidizing (anammox) bacteria of phylum Planctomycetes origin have been identified to be responsible for N removal in terrestrial and aquatic environments through combined NH4+ oxidation and NO2 reduction. Anaerobic ammonium oxidation mediated by anammox bacteria has been noted to be a key process of biogeochemical N cycle in various ecosystems. It was also possible to have anammox processes in flooded paddy fields because of the low oxygen habitat conditions. To investigate the existence of anammox bacteria and the bacteria community diversity response to applied N fertilizer in paddy fields, anammox bacteria community structures in paddy fields were investigated with the aid of denaturing gradient gel electrophoresis and cloning sequencing by assay 16S rRNA gene in the third year of N fertilizer experiment in the field. DGGE images of 16S rRNA gene in surface or root-zone soil showed rich anammox bacteria in paddy soils. The numbers of DGGE band in the images of surface soil or root-zone soil under high N level treatment N3: 225 kg(N)·hm^-2] were greater than those under other N levels N2: 150 kg(N)·hm^-2, N1: 75 kg(N)·hm^-2 and CK: without fertilizer]. The Shannon-Wiener index based on the number and density of DGGE band showed significantly (P < 0.05) higher diversity of anammox bacteria in surface soil or root-zone soil under N3 treatment than N2, N1 or CK treatments. At the same time, Shannon-Wiener index of anammox bacteria in surface soil was markedly (P < 0.05) higher than in root-zone soil under N3 treatment. Redundancy discriminate analysis (RDA) based on 16S rRNA gene DGGE profiles showed significant correlation (P = 0.006) of anammox bacteria community structure in surface soils of paddy fields with different levels of N fertilizer application. RDA plot depicted that anammox bacteria community structure in surface soil under N3 treatment obviously differed from that under N1 or CK treatment. Furthermore, 18 DNA sequences cloning from DGGE band was obtained and logged in GenBank. The findings demonstrated that anammox bacteria community structure in paddy soils strongly responded to intensive N fertilizer use especially in surface paddy soils. Anammox bacteria possibly played a critical role in N cycle in paddy soil ecosystem.