Abstract Dissolved oxygen (DO) content is crucial for the development and health of aquatic animals. DO content is closely related to the antioxidant response of aquatic animals, while the interplay between DO content and the gut microbiota of aquatic animals is unclear. Thus, the objective of this study was to compare the changes in gut microbiota in Bostrichthys sinensis under normoxic (CT group) and hypoxic (Y group) conditions. Superoxide dismutase and catalase activities were similar in the CT and Y groups. The diversity and richness of the community decreased significantly in the Y group, concurrent with an altered composition in the gut microbiota. A dissimilarity test demonstrated that the structure of the gut microbiota was strictly separate between the CT and Y groups. The relative abundance of Gammaproteobacteria increased significantly while the relative abundance of Deltaproteobacteria decreased significantly in the Y group compared to the CT group. A significant increase in the relative abundance of Proteus was observed in the Y group, whereas the relative abundance of Desulfovibrio declined sharply. A network analysis revealed that average connectivity and sub-module numbers decreased in the Y group, suggesting that the complexity, efficiency, and robustness of the gut microbiota network in B. sinensis declined distinctly under the hypoxic condition. Clostridia was the main component serving as a module hub in the CT and Y group networks. Furthermore, most of the shared operational taxonomic units (OTUs) belonged to Clostridia. These results suggested that Clostridia both occupied an important position in the two networks of the B. sinensis gut microbiota, however the niche of Clostridia was notably altered based on its interactions with other species under the hypoxic condition. The interactions between Clostridia and other OTUs in the Y group network converted, indicating that a hypoxic condition could affect the function of Clostridia in the network. The homeostasis of the B. sinensis gut microbiota was disrupted under the hypoxic condition due to deterioration in the network structure resulting from a decrease in the number of module hubs and average connectivity. Microbial metabolism could be affected by the hypoxic conditions, and the abundant microbial functional pathways had advantage to the survival of B. sinensis. This study revealed the effects of DO on the composition of gut microbiota in B. sinensis and further illustrated the importance of interspecific interactions and species roles for evaluating the development and health of B. sinensis using an ecological network analysis of the gut microbiota.

中文翻译：

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常氧和缺氧条件对中华鲆免疫反应和肠道菌群的影响

摘要 溶解氧 (DO) 含量对水生动物的发育和健康至关重要。DO含量与水生动物的抗氧化反应密切相关，而DO含量与水生动物肠道微生物群之间的相互作用尚不清楚。因此，本研究的目的是比较常氧（CT组）和缺氧（Y组）条件下中华鲟肠道微生物群的变化。CT和Y组的超氧化物歧化酶和过氧化氢酶活性相似。Y 组群落的多样性和丰富度显着下降，同时肠道微生物群的组成发生了变化。一项差异性测试表明，CT 组和 Y 组之间的肠道微生物群结构是严格分开的。与CT组相比，Y组Gammaproteobacteria的相对丰度显着增加，而Deltaproteobacteria的相对丰度显着降低。在Y组中观察到变形杆菌的相对丰度显着增加，而脱硫弧菌的相对丰度急剧下降。网络分析显示，Y 组的平均连通性和子模块数下降，表明在缺氧条件下，中华白菜肠道微生物群网络的复杂性、效率和稳健性明显下降。梭菌是 CT 和 Y 组网络中充当模块中心的主要组件。此外，大多数共享操作分类单元 (OTU) 属于梭菌属。这些结果表明，梭菌在中华双歧杆菌肠道微生物群的两个网络中都占有重要地位，但梭菌的生态位因在缺氧条件下与其他物种的相互作用而发生显着改变。Y 组网络中梭菌与其他 OTU 之间的相互作用发生了转换，表明缺氧条件可能会影响梭菌在网络中的功能。由于模块集线器数量和平均连通性的减少导致网络结构恶化，在缺氧条件下，中华双歧杆菌肠道微生物群的稳态被破坏。微生物代谢受低氧条件影响，丰富的微生物功能通路有利于中华白菜的生存。