Gut microbiota could facilitate host to defense diseases, but fish–microbiota interactions during viral infection and the underlying mechanism are poorly understood. We examined interactions and responses of gut microbiota to grass carp reovirus (GCRV) infection in Ctenopharyngodon idellus, which is the most important aquaculture fish worldwide. We found that GCRV infection group with serious haemorrhagic symptoms (G7s) showed considerably different gut microbiota, especially with an abnormally high abundance of gram‐negative anaerobic Cetobacterium somerae. It also showed the lowest (p < 0.05) alpha‐diversity but with much higher ecological process of homogenizing dispersal (28.8%), confirming a dysbiosis of the gut microbiota after viral infection. Interestingly, signaling pathways of NOD‐like receptors (NLRs), toll‐like receptors (TLRs), and lipopolysaccharide (LPS) stimulation genes were significantly (q‐value < 0.01) enriched in G7s, which also significantly (p < 0.01) correlated with the core gut microbial genera of Cetobacterium and Acinetobacter. The results suggested that an expansion of C. somerae initiated by GCRV could aggravate host inflammatory reactions through the LPS‐related NLRs and TLRs pathways. This study advances our understanding of the interplay between fish immunity and gut microbiota challenged by viruses; it also sheds new insights for ecological defense of fish diseases with the help of gut microbiota.

中文翻译：

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寄主—菌群相互作用和对草鱼呼肠孤病毒感染的反应

肠道菌群可以促进防御疾病的宿主，但是人们对病毒感染过程中鱼类-菌群的相互作用及其潜在机制知之甚少。我们研究的互动和肠道菌群的反应，草鱼呼肠孤病毒感染的草鱼，这是最重要的水产养殖鱼类全世界。我们发现具有严重出血症状（G7s）的GCRV感染组表现出明显不同的肠道菌群，尤其是革兰氏阴性厌氧性结直肠细菌Somerae的异常高丰度。它也显示出最低的（p<0.05）α-多样性，但具有更高的均匀分散生态过程（28.8％），证实了病毒感染后肠道菌群的营养不良。有趣的是，NOD样受体（NLRs），toll​​样受体（TLRs）和脂多糖（LPS）刺激基因的信号通路显着（q值<0.01）富含G7s，这也显着（p <0.01）相关具有肠杆菌和不动杆菌的核心肠道微生物属。结果表明，C。somerae的扩展由GCRV引发的炎症可通过LPS相关的NLR和TLR途径加剧宿主的炎症反应。这项研究提高了我们对鱼类免疫力和病毒挑战的肠道菌群之间相互作用的理解。它还借助肠道菌群为鱼类疾病的生态防御提供了新见识。