中文摘要：

本研究以nirS基因为分子标记，将PCR、克隆文库构建与测序和典范对应分析相结合，对珠江口表层沉积物nirS型反硝化微生物的群落多样性进行了研究。3个站位共获得180个nirS基因克隆子，隶属于62个OTUs，氨基酸序列的相似性在50％-100％之间。各站位OTU分布格局差异明显，范围在19—33之间，表现出高度的多样性。系统进化分析表明，62个OTUs形成了5个类群，分别与河口、海洋沉积物、海岸养殖排放废水、富营养化海湾及海水养殖沉积物等的反硝化微生物聚类在一起，表明珠江口作为海淡水交汇区具有独特的反硝化微生物群落分布格局，同时也指示了珠江口氮污染及富营养化程度。典范对应分析结果表明，盐度、氮相关营养盐水平（PON／TN、NH4-N、NO2-N和N03．N）可能是影响其分布格局的重要因素。

英文摘要：

Diversity of denitrifying bacteria by encoding nirS gene from surface sediments and the major contributing parameter from environment in the Pear River were studied using PCR, clone library construction, sequencing and canonical correspondence analysis. Totally 180 clones by encoding nirS gene belong to 62 OTUs were obtained from three sampling stations. Three stations with different distribution patterns of OTUs revealed high diversity of denitrifying bacteria by encoding nirS gene. The similarity in the deduced amino acid sequence of all OTUs ranged from 50% to 100%. The numbers of OTUs from three stations ranged from 19 to 33. The phylogenetic analysis showed that 62 OTUs were divided into five groups, whose amino acid sequences were highly similar to those of denitrifying cultured or uncultured bacteria from sediments of ocean, esturary and mariculture, aquaculture wastewater and bay of eutrophication. The special community structure of denitrifying bacteria from sediments suggested the significant correlate with the fresh and salt water mixing and the nitrogen pollution in the Pear River Esturary. Canonical correspondence analysis also indicated that nitrogen nutrient and salinity were the major contributing parameter for the diversity and spatial distribution of denitrifying bacteria from sediments in the Pear River Esturary.