Xu Zhimeng, Wang Min, Wu Wenxue, Li Yifan, Liu Qian, Han Yuye, Jiang Yong, Shao Hongbing, McMinn Andrew, Liu Hongbin
College of Marine Life Sciences, Ocean University of China, Qingdao, China.
Division of Life Science, The Hong Kong University of Science and Technology, Kowloon, Hong Kong.
Front Microbiol. 2018 Aug 28;9:2023. doi: 10.3389/fmicb.2018.02023. eCollection 2018.
Marine microbial eukaryotes are ubiquitous, comprised of phylogenetically diverse groups and play key roles in microbial food webs and global biogeochemical cycling. However, their vertical distribution in the deep sea has received little attention. In this study, we investigated the composition and diversity of the eukaryotes of both 0.2-3 μm and >3 μm size fractions from the surface to the hadal zone (8727 m) of the Mariana Trench using Illumina MiSeq sequencing for the 18S rDNA. The microbial eukaryotic community structure differed substantially across size fractions and depths. Operational taxonomic unit (OTU) richness in the >3 μm fraction was higher than that in the 0.2-3 μm fraction at the same depth. For the 0.2-3 μm fraction, sequences of Retaria (Rhizaria) were most abundant in the surface water (53.5%). Chrysophyceae (Stramenopiles) sequences dominated mostly in the samples from water depths below 1795 m. For the >3 μm fraction, sequences of Dinophyceae (Alveolata) were most abundant in surface waters (49.3%) and remained a significant proportion of total sequences at greater depths (9.8%, on average). Retaria sequences were abundant in samples of depths ≥1000 m. Amoebozoa and Apusozoa sequences were enriched in the hadal sample, comprising 38 and 20.4% of total sequences, respectively. Fungi (Opisthokonta) sequences were most abundant at 1759 m in both size fractions. Strong positive associations were found between Syndiniales (mainly MALV-I and MALV-II) and Retaria while negative associations were shown between MALV-II and Fungi in a co-occurrence analysis. This study compared the community structure of microbial eukaryotes in different zones in the deep sea and identified a distinct hadal community in the larger size fraction, suggesting the uniqueness of the eukaryotes in the biosphere in the Mariana Trench.
海洋微生物真核生物无处不在，由系统发育上不同的类群组成，在微生物食物网和全球生物地球化学循环中发挥着关键作用。然而，它们在深海中的垂直分布很少受到关注。在本研究中，我们使用Illumina MiSeq测序技术对18S rDNA进行分析，研究了马里亚纳海沟从表层到超深渊带（8727米）中0.2 - 3微米和大于3微米粒径级分的真核生物的组成和多样性。微生物真核生物群落结构在不同粒径级分和深度之间存在显著差异。在相同深度下，大于3微米粒径级分中的可操作分类单元（OTU）丰富度高于0.2 - 3微米粒径级分。对于0.2 - 3微米粒径级分，有孔虫纲（根足亚纲）的序列在表层水中最为丰富（53.5%）。金藻纲（不等鞭毛类）序列主要在水深低于1795米的样本中占主导地位。对于大于3微米粒径级分，甲藻纲（囊泡虫类）的序列在表层水中最为丰富（49.3%），并且在更深的深度仍占总序列的显著比例（平均9.8%）。有孔虫纲序列在深度≥1000米的样本中丰富。变形虫门和无尾鞭毛虫门序列在超深渊样本中富集，分别占总序列的38%和20.4%。真菌（后鞭毛生物）序列在两个粒径级分中均在1759米处最为丰富。在共现分析中发现，聚缩虫目（主要是MALV - I和MALV - II）与有孔虫纲之间存在强正相关，而MALV - II与真菌之间存在负相关。本研究比较了深海不同区域微生物真核生物的群落结构，并在较大粒径级分中鉴定出一个独特的超深渊群落，表明马里亚纳海沟生物圈中真核生物的独特性。
