北运河沉积物中氨氧化微生物的群落特征

Diversity and abundance of ammonia-oxidizing prokaryotes in surface sediments in Beiyun River

采用T-RFLP、RT-qPCR和克隆测序等分子生物学技术,以氨单加氧酶基因（amoA）为分子标记,研究了北运河表层沉积物中氨氧化古菌（AOA）和氨氧化细菌（AOB）的群落多样性、丰度、系统发育及其与环境因子的响应关系.结果表明,沉积物中AOB的群落多样性和丰度均高于AOA,是北运河沉积物中氨氧化过程的主要功能微生物.沉积物中氨氧化微生物群落结构沿干流和支流存在明显的空间分异,而AOA的种类组成空间差异较小;沉积物的氨氮（NH4＋）和硝态氮（NO3-＋NO2-）是影响氨氧化微生物群落特征的主要因子,AOB对环境变化的敏感性更高;AOA和AOB的amoA基因拷1贝数分别为1.32×10^5～ 1.91×10^6copies/g、5.39× 10^5～8.3×10^6copies/g.闸坝下游沉积物的氨氧化微生物丰度最高.系统发育分析表明,amoA基因序列多属于土壤/沉积物分支,较多AOB的克隆序列与土壤亚硝化螺菌属（Nitrosospira）的类群相似性可达98％.受污水处理厂退水的影响,部分amoA基因序列与污水处理厂废水和活性污泥中发现的类群同源性高.污染物质来源、支流汇入和闸坝拦截对河流沉积物氨氧化微生物的群落特征影响显著.

The community diversity, abundance, and phylogeny of ammonia-oxidizing archaea （AOA） and bacteria （AOB） in the surface sediments of Beiyun River were investigated using various molecular techniques targeting the ammonia monooxygenase （amoA） genes. Diversity and abundance of bacteria were higher than those of archaea. AOB were the dominant ammonia-oxidizing microorganisms in Beiyun River. For AOB, sediment samples from main stream and tributary were cluster into two categories. In contrast, AOA communities showed relatively slight site-specific difference. Correlation analysis indicated that concentration of ammonia （NH4＋） and the sum of nitrite and nitrate of sediment were the main factors affecting the community compositions of ammonia-oxidizing prokaryotes, and AOB was much more sensitive to environmental change. The amoA gene copy numbers of AOA and AOB in wet sediment ranged from 1.32× l 0^5 to 1.91× 10^6copies/g and from 5.39× 10^5to 8.3 ×10^6copies/g, respectively. The sediment ammonia-oxidizing prokaryotes in downstream of the dam showed the highest abundance. Phylogenetic analysis revealed that most of the cloned amoA sequences of both AOA and AOB belonged to soil/sediment group. A considerable proportion of AOB sequences were highly affiliated with soil Nitrosospira lineage. Because of the influence from wastewater treatment plant effluent, some amoA sequences were similar to those recovered from activated sludge and wastewater.