中文摘要：

从长江口邻近海域沉积物中提取好氧氨氧化细菌（aerobic ammonium-oxidizing bacteria，AOB）的DNA，通过构建硝化作用氨单加氧酶基因文库并划分操作分类单元（OTU）的方法，揭示好氧氨氧化细菌群落结构多样性。结果显示，研究的两个站位（G6站和33站）分别获得417和428个amoA基因克隆，其序列皆属于变形杆菌的β-亚纲，但与此亚纲中已有明确分类信息菌株的amoA基因序列距离较远，相似度较低；利用DOTUR软件将相似度不小于97％的序列归为一个OTU，两站均得到11个OTUs，但离岸较近的G6站沉积物中B．AOB具有较高的多样性，而离岸较远的33站则多样性较低，且两个站位中的优势类群差异明显。

英文摘要：

The clone libraries of ammonium monooxygenase encoding gene （amoA） in the sediments from adjacent waters of Cbangjiang Estuary were constructed and grouped into the operational taxonomic units （OTUs） to determine the community diversity of aerobic ammonium-oxidizing bacteria （AOB）. A total of 417 and 428 sequences were obtained from station G6 and 33 respectively. Pbylogenetic analysis with the aligned sequences showed that the amoA sequences from two stations were all in the β-subdivision of Proteobacteria,but there was a further phylogenetic distance between them and the ones from strains which have been classified clearly. 11 OTUs from two stations were grouped respectively based on a 3% amoA gene sequence distance cutoff with the DOTUR program. The results showed a higher diversity of β-AOB in the sediment of station G6 offshore closer than station 33 offshore further. The dominated β-AOB populations of the two stations were obviously different.