长江口外低氧区及其邻近海域表层沉积物反硝化微生物多样性和分布特征

Diversity and distribution of denitrifying microorganisms in the surface sediments of the hypoxic zone near the Changjiang Estuary and its offshore

摘要:

[目的] 微生物参与的反硝化是河口区氮损失的主要途径。[方法] 本研究采用Illumina MiSeq测序方法，研究了长江口外低氧区及其邻近海域表层沉积物中nirS型和nirK型反硝化微生物群落的多样性和分布特征。[结果] 样品共检测到346个nirS Operational Taxonomic Units和267个nirK Operational Taxonomic Units，根据采样地的环境特征及nirS型和nirK型反硝化微生物群落聚类分析结果将所有Operational Taxonomic Units划分为低氧区、南部区域及外部深水区，其中外部深水区的样品nirS功能基因的多样性最高。各实验样地优势Operational Taxonomic Units在系统进化关系上可分为多个不同的簇。此次发现的所有优势Operational Taxonomic Units均属于未被培养的菌群，其中部分Operational Taxonomic Units还是首次被发现。此外还发现nirS功能基因对低氧区的环境适应性更好。[结论] 我们的研究结果表明广泛存在的反硝化微生物在河口沉积物的氮循环中发挥重要作用。

关键词:长江口;低氧区;nirS;nirK

Abstract:

[Objective] Microbial denitrification is the essential process to transform nitrate into nitrogen gas in estuarine environment. [Methods] In the present study, we investigated the diversity and distribution of the nirS-type and nirK-type denitrifying microbial communities in the surface sediments of the hypoxic zone near the Changjiang Estuary and in the East China Sea by Illumina MiSeq sequencing approach. [Results] A total of 346 nirS-type and 267 nirK-type Operational Taxonomic Units were detected. Environmental characteristics of sampling site and cluster analysis of nirS and nirK divided all Operational Taxonomic Units into hypoxic, southern and deep-water groups, and the samples from the deep-water group had the highest diversity of nirS functional genes. Furthermore, the dominant Operational Taxonomic Units phylogenetically formed several clusters, representing by Operational Taxonomic Units from distinct groups. All the dominant Operational Taxonomic Units were uncultured and some of them were first retrieved. Likewise, nirS gene was more adaptable to the hypoxic condition.[Conclusion] Our results indicate that widespread denitrifying microorganisms play a critical role in nitrogen cycle in the estuarine sediments.

Key words:Changjiang Estuary;hypoxic zone;nirS;nirK