Zhang Hongxi, Wei Taoshu, Li Qingmei, Fu Liang, Li Manjie, He Lisheng, Wang Yong
Institute of Deep Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China.
University of Chinese Academy of Sciences, Beijing, China.
Front Microbiol. 2024 Jul 29;15:1420899. doi: 10.3389/fmicb.2024.1420899. eCollection 2024.
The Yongle blue hole (YBH), situated in the South China Sea, represents a compelling subject of study in marine microbiology due to its unique redox-layered microbial ecosystems. However, the diversity and ecology of microbial eukaryotes within the YBH remains underexplored. This study endeavors to bridge this gap through the application of the microbial filtration and fixation (ISMIFF) device to collect 0.22-30 μm microbial samples from 21 water layers of YBH. Subsequent extraction of 18S rRNA metagenomic reads of 21 metagenomes and 10 metatranscriptomes facilitated a comprehensive analysis of community structures. Findings revealed a pronounced superiority in the diversity and richness of eukaryotic microorganisms in the oxic zone compared to its suboxic and anoxic counterparts. Notably, Dinophyceae and Maxillopoda emerged as the predominant taxa based on the analysis of the 18S rRNA reads for the V4 and V9 regions, which showed stratification In their relative abundance and suggested their potential role in the thermo-halocline boundaries and oxic-anoxic interface. Specifically, In these eukaryotic microbial communities, Dinophyceae exhibited significant abundance at 20 m (20.01%) and 105 m (26.13%) water depths, while Maxillopoda was prevalent at 40 m (22.84%), 80 m (23.19%), and 100 m (15.42%) depths. A part of these organisms, identified as larvae and protists, were likely attracted by swarming chemosynthetic bacterial prey prevailing at the thermo-halocline boundaries and oxic-anoxic interface. Furthermore, the phylogenetic relationships of the major 18S operational taxonomic units (OTUs) showed a close adjacency to known species, except for three Dinophyceae OTUs. In conclusion, this study provides critical insights into the vertical distribution and transcriptional activity of <30-μm eukaryotic microbes, shedding light on the taxonomic novelty of eukaryotic microorganisms within the semi-enclosed blue holes.
永乐蓝洞（YBH）位于中国南海，因其独特的氧化还原分层微生物生态系统，成为海洋微生物学中一个引人注目的研究对象。然而，永乐蓝洞内部微生物真核生物的多样性和生态学仍未得到充分探索。本研究通过应用微生物过滤与固定（ISMIFF）装置，从永乐蓝洞的21个水层收集0.22 - 30μm的微生物样本，试图填补这一空白。随后对21个宏基因组和10个宏转录组的18S rRNA宏基因组读数进行提取，有助于对群落结构进行全面分析。研究结果显示，与次氧区和缺氧区相比，有氧区真核微生物在多样性和丰富度上具有明显优势。值得注意的是，基于对V4和V9区域的18S rRNA读数分析，甲藻纲和颚足纲成为主要分类群，它们的相对丰度呈现分层现象，表明它们在温跃层边界和有氧 - 缺氧界面可能发挥的作用。具体而言，在这些真核微生物群落中，甲藻纲在水深20米（20.01%）和105米（26.13%）处表现出显著丰度，而颚足纲在水深40米（22.84%）、80米（23.19%）和100米（15.42%）处较为普遍。这些生物中一部分被鉴定为幼虫和原生生物，它们可能被在温跃层边界和有氧 - 缺氧界面大量存在的趋化合成细菌猎物所吸引。此外，除了三个甲藻纲OTU外，主要的18S操作分类单元（OTU）的系统发育关系与已知物种显示出密切的邻接关系。总之，本研究为<30μm真核微生物的垂直分布和转录活性提供了关键见解，揭示了半封闭蓝洞内部真核微生物的分类新特性。
