Zhu Xiao-Yu, Liu Jiwen, Xue Chun-Xu, Tian Jiwei, Zhang Xiao-Hua
College of Marine Life Sciences, Ocean University of China, Qingdao, China.
Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
Front Microbiol. 2021 Jan 18;11:603692. doi: 10.3389/fmicb.2020.603692. eCollection 2020.
Microbial eukaryotes are widespread and play important roles in marine ecosystems. However, their ecological characteristics in the deep sea (>1,000 m), especially hadal trenches, were largely unknown. Here, we investigated the diversity and metabolic potentials of microbial eukaryotes along the whole water column of the Mariana Trench by metagenomics. Our results showed clear depth-related distribution of microbial eukaryotic community and associated metabolic potentials. Surface seawater was dominated by phototrophic/mixotrophic groups (e.g., Dinoflagellata) and genes involved in biosynthesis (photosynthesis and fatty acid biosynthesis), while deep (bathypelagic and/or hadal) seawaters were enriched with heterotrophic groups (e.g., Bicoecea) and genes related to digestion (lysosomal enzymes and V-type ATPase) and carbohydrate metabolism. Co-occurrence analysis revealed high intra-domain connectivity, indicating that microbial eukaryotic composition was more influenced by microbial eukaryotes themselves than bacteria. Increased abundance of genes associated with unsaturated fatty acid biosynthesis likely plays a role in resisting high hydrostatic pressure. and genes, responsible for the formation and stabilization of DNA structure, were unique and abundant in the hadal zone and thus may be helpful to stabilize DNA structure in the deep sea. Overall, our results provide insights into the distribution and potential adaptability of microbial eukaryotes in the hadal zone.
微生物真核生物广泛分布，在海洋生态系统中发挥着重要作用。然而，它们在深海（>1000米），尤其是海沟中的生态特征在很大程度上尚不清楚。在此，我们通过宏基因组学研究了马里亚纳海沟整个水柱中微生物真核生物的多样性和代谢潜力。我们的结果表明，微生物真核生物群落及其相关代谢潜力呈现出明显的与深度相关的分布。表层海水以光合营养/混合营养类群（如甲藻）以及参与生物合成（光合作用和脂肪酸生物合成）的基因为主，而深层（深海和/或超深渊）海水则富含异养类群（如双鞭毛虫纲）以及与消化（溶酶体酶和V型ATP酶）和碳水化合物代谢相关的基因。共现分析揭示了高域内连通性，表明微生物真核生物的组成受微生物真核生物自身的影响大于细菌。与不饱和脂肪酸生物合成相关基因丰度的增加可能在抵抗高静水压力方面发挥作用。并且，负责DNA结构形成和稳定的基因在超深渊带独特且丰富，因此可能有助于在深海中稳定DNA结构。总体而言，我们的结果为微生物真核生物在超深渊带的分布和潜在适应性提供了见解。
