中文摘要：

厌氧氨氧化（anaerobic ammonium oxidation,anammox）在海洋氮素循环中起了重要作用,而有关天然淡水生态系统中anammox的研究报道并不多.本研究采用16SrRNA基因克隆文库技术首次考察了西湖淡水底泥中anammox菌的分布与种群多样性水平.16SrRNA系统发育分析表明,西湖底泥中的anammox菌种群多样性水平较高,明显高于目前已报道的大部分自然生态系统,检测结果发现Brocadia,Kuenenia,Scalindua三个属的anammox菌共存于西湖底泥中.此外,本研究在西湖底泥中还发现了两个新的anammox菌序列群,其与目前已知anammox菌的序列相似度都较低（分别仅为92.9%～93.3%和91.6%～92.7%）.与海洋底泥不同（海洋底泥中Scalindua属的anammox菌占主导地位）,西湖淡水底泥中Kuenenia属的anammox菌明显占优.

英文摘要：

Anaerobic ammonium oxidation（anammox） plays a very important role in the marine nitrogen cycle.But reports on the distribution of anammox bacteria in natural freshwater ecosystems are few.We firstly investigated the distribution and diversity of anammox bacteria in the sediment of West Lake by constructing 16S rRNA gene colony libraries.Phylogenetic analysis of 16S rRNA genes showed that the sequences of Brocadia,Kuenenia and Scalindua could be simultaneously detected in the West Lake sediment,which showed a much higher diversity of anammox bacteria than most reported natural ecosystems.Furthermore,two new anammox bacterial clusters which only showed 92.9%~93.3% and 91.6%~92.7% sequence identity to described anammox bacteria were found in the West Lake sediments.The higher anammox bacterial diversity found in the sediment indicated a large variety of suitable ecological niches are provided for different anammox bacteria in West Lake freshwater ecosystems.As opposed to marine sediments where Scalindua bacteria dominated anammox guilds,Kuenenia organisms appeared to be the most common species in West Lake sediment.