太湖竺山湾沉积物中氨氧化原核生物的垂直分布与多样性

原核生物驱动的氨氧化过程对于富营养化湖泊的氮循环具有重要意义。为了解太湖藻型湖区沉积物中氨氧化原核生物的垂直分布和多样性特征,采用分子生态学方法,对竺山湾沉积物剖面中氨单加氧酶基因(amoA)或16S rRNA基因等特征分子标记的变化和序列特征进行了分析。结果表明,氨氧化细菌(ammonia-oxidizing bacteria,AOB)和氨氧化古菌(ammonia-oxidizing archaea,AOA)共存于沉积物各层。AOB的优势种在5cm深度以下发生明显改变,这可能与沉积物氧化还原电位及铵态氮的变化有关;所有细菌amoA序列均属亚硝化单胞菌(Nitrosomonas)。AOA群落结构自表层至7cm深度变化不大,所有古菌amoA序列分属泉古菌CG1.1b和CG1.1a两大类群,这可能与太湖形成历史上的海陆交替过程有关。此外,沉积物各层均未发现典型厌氧氨氧化(anaerobic ammonium oxidation,anammox)细菌16S rRNA基因序列。这些发现丰富了对太湖藻型湖区氨氧化原核生物分布、多样性及环境调控原理的认识,对理解富营养化湖泊氨氧化规律、认识湖泊生态系统氮循环功能具有借鉴意义。

Vertical distribution and diversity of ammonia-oxidizing prokaryotes in a sediment core from Zhushan Bay, Lake Taihu

Prokaryotes-driven ammonia oxidation plays an important role in global nitrogen cycling. The vertical distribution and diversity of ammonia oxidizing prokaryotes in a sediment core collected in Zhushan Bay, which is located in the northern part of Lake Taihu and being strongly influenced by heavy eutrophication and algae blooms. The samples were investigated by molecular approaches targeting at either the ammonia monooxygenase subunit A (amoA) or 16S rRNA gene. Our findings showed that both ammonia-oxidizing bacteria (AOB) and archaea (AOA) coexisted in the sediment profile. It was clearly indicated by denaturing gradient gel electrophoresis (DGGE) pattern that the dominating species of AOB shifted below 5 cm depth of the sediment core, highlighting the influences of key environmental factors, i.e. oxidation-reduction potential and NH+4-N, on AOB community; the dominance of Nitrosomonas oligotropha lineage sequences also suggested the environmental selection of AOB population in Lake Taihu. In contrast, the community composition of AOA in top 7 cm sediment was less variable. All retrieved archaeal amoA sequences belonged to either Soil & other environments or Marine & other environments lineages, which correspond to the CG1.1b and CG1.1a of Crenarchaeota, respectively. On the other hand, the anaerobic ammonium oxidizing (anammox) bacteria-like 16S rRNA gene sequences were retrieved at 5 cm depth only, which are distantly related to the known anammox bacteria. In this communication, we report for the first time a detailed simultaneous study on the three groups of ammonia-oxidizing prokaryotes in Lake Taihu sediment, which would enrich our understanding for ammonia oxidation process and nitrogen cycles in eutrophic lake ecosystems.