洞庭湖岸边带沉积物氨氧化古菌的丰度、多样性及对氨氧化的贡献

采用分子生物学的方法(定性/定量PCR、克隆文库)对洞庭湖岸边带沉积物中氨氧化古菌(Ammonia-Oxidizing Archaea,AOA)进行分子水平的多样性和丰度分析,并结合硝化速率潜势(Potential Nitrification Rate,PNR)剖析AOA在洞庭湖岸边带沉积物中氨氧化的作用.采用实时荧光定量PCR技术对氨氧化古菌AOA和氨氧化细菌(Ammonia-Oxidizing Bacteria,AOB)进行靶向amoA基因(氨氧化关键功能基因)的定量分析,发现古菌amoA基因的丰度为1.49×107 ～ 1.97×10s copies· g-1(以干土计),高于细菌amoA基因丰度(1.52×104 ～2.45×106copies·g-1,以干土计)1～4个数量级.洞庭湖岸边带沉积物硝化速率潜势为1.11 ～6.47 nmol·g-1·h-1(以N计),比细胞硝化速率为0.55 ～1.68 fmol· cell-1·d-1(以NH3计).硝化速率潜势与古菌amoA基因丰度之间呈现正向变化趋势,而与细菌amoA基因丰度呈负向变化趋势,指示了低氨氮环境下AOA在氨氧化过程中的主导作用.生物多样性分析表明,经酶切分型后得到的22个古菌amoA基因序列以97％的相似度划分为8个独立操作单元(Operational Taxonomic Unit,OTU).系统发育分析显示,OTU 1～6(14个序列)属于第一分支,OTU 7～8(8个序列)属于第二分支,且均属于一个新命名的古菌类群——奇古菌门(Thaumarchaeota).

Abundance, biodiversity and contribution to ammonia oxidization of ammonia-oxidizing archaea in littoral sediments of Dongting Lake

With the method of molecular biology (qualitative/quantitative PCR and clone libraries), the biodiversity and abundance of ammonia-oxidizing archaea (AOA) from the littoral sediments of Dongting Lake were analyzed at the molecular level. At the same time, the contribution of AOA to ammonia oxidization was also analyzed in combination with the potential nitrification rate (PNR). The number of archaeal amoA gene (the key functional gene of AOA) was measured at 1.49×10⁷~1.97×10⁸ copies·g^-1 dry soil, 1~4 orders of magnitude larger than that of bacterial amoA gene (1.52×10⁴~2.45×10⁶ copies·g^-1 dry soil). The PNR of littoral sediments of Dongting Lake was between 1.11 and 6.47 nmol·g^-1·h^-1, and cell-specific nitrification rates for AOA and AOB (combined) ranged from 0.55 to 1.68 fmol·cell^-1·d^-1. PNR correlated positively with the number of archaeal amoA gene and negatively with bacterial amoA gene, which indicated the dominant role of AOA in ammonia oxidization process in environments with low ammonium concentration. In the analysis of biodiversity, sequences sharing 97% similarity were grouped into the same operational taxonomic unit (OTU), and 8 OTUs were obtained from 22 archaeal amoA gene sequences selected after distinguished by the restriction endonuclease. Phylogenetic analysis indicated that OTU 1~6 (14 sequences) belonged to cluster 1, while OTU 7~8 (8 sequences) belonged to cluster 2, and AOA in littoral sediments of Dongting Lake were all affiliated to a newly named archaea cluster "Thaumarchaeota".