Xu Dapeng, Li Ran, Hu Chen, Sun Ping, Jiao Nianzhi, Warren Alan
State Key Laboratory of Marine Environmental Science, Institute of Marine Microbes and Ecospheres, Xiamen UniversityXiamen, China.
Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment and Ecology, Xiamen UniversityXiamen, China.
Front Microbiol. 2017 Jun 14;8:1121. doi: 10.3389/fmicb.2017.01121. eCollection 2017.
To study the diversity and metabolic activity of microbial eukaryotes in the water column of the South China Sea, genomic DNA and RNA were co-extracted from samples collected down to bathyal depth at two sites. V9 regions of both SSU rRNA gene and its transcript (cDNA) were amplified and sequenced using high throughput sequencing. Our study revealed: (1) DNA and RNA datasets showed significant differences in microbial eukaryote community composition, with the variability between the two datasets for the same sample exceeding that between samples within each dataset, indicating that nucleic acid source overrode environmental factors in determining the composition of microeukaryotes; (2) despite the differences in community composition between the two datasets, both DNA and RNA revealed similar depth-related distribution patterns of microbial eukaryotes; (3) using the ratio of RNA: DNA as a proxy of relative metabolic activity, a depth-related pattern was found for the relative metabolic activity of some but not all groups of microbial eukaryotes, with the highest activity for the groups with depth-related pattern usually found in the middle water layers; and (4) the presence of live and active photoautotrophic microbial eukaryotes in the deep ocean was confirmed, indicating that they play an important role in controlling the deep-sea organic carbon pool. Overall, our study sheds light on the diversity and activity of microbial eukaryotes in the water column of a tropical oligotrophic ocean and their potential contributions in the downward transportation of organic material from the surface ocean to the deep via the biological pump.
为研究南海水柱中微生物真核生物的多样性和代谢活性，从两个站点采集了直至半深海深度的样本，共提取了基因组DNA和RNA。使用高通量测序技术对小亚基核糖体RNA基因（SSU rRNA）及其转录本（cDNA）的V9区域进行了扩增和测序。我们的研究揭示：（1）DNA和RNA数据集在微生物真核生物群落组成上存在显著差异，同一样本的两个数据集之间的变异性超过了每个数据集中样本之间的变异性，这表明在决定微型真核生物组成方面，核酸来源比环境因素更为重要；（2）尽管两个数据集的群落组成存在差异，但DNA和RNA都揭示了微生物真核生物与深度相关的相似分布模式；（3）以RNA:DNA的比率作为相对代谢活性的指标，发现部分而非所有微生物真核生物类群的相对代谢活性呈现出与深度相关的模式，具有与深度相关模式的类群通常在中水层具有最高活性；（4）证实了深海中存在活的且活跃的光合自养微生物真核生物，这表明它们在控制深海有机碳库方面发挥着重要作用。总体而言，我们的研究揭示了热带贫营养海洋水柱中微生物真核生物的多样性和活性，以及它们通过生物泵在将表层海洋中的有机物质向下输送到深海过程中的潜在贡献。
