Fish harbour complex and dynamic microbiota in their mucosal surfaces. Due to the vital role of commensal microbiota in many biological functions including growth enhancement, nutrition, development, metabolism and immune response, many scholars have begun to refer to the microbiome as an ‘extended self’. Several studies have indicated that a normal microbiota contributes to fish health, and disturbances in microbial communities may lead to secondary infections and disease. Under evolutionary selective forces, fish have developed excellent innate immune mechanisms and an adaptive immune system composed of B cells and T cells to discriminate between beneficial and opportunistic bacteria for microbiome homeostasis. Many functional studies have demonstrated the involvement of immune cells, cytokines and Igs in maintaining microbiome homeostasis, and many beneficial microbes contribute to improving the immune barrier against external threats. Additionally, many host-derived probiotics have been empirically used in the aquaculture sector and have been demonstrated to provide effective protection against fish diseases. Although little is known about the interactions between microbiota and the mucosal immune system in fish compared to mammals, managing aquaculture system microbiota may represent a promising alternative to antibiotics for disease prevention and control. This review thus provides an updated and comprehensive summary of currently characterized microbe compositions in fish mucosal tissues. Thereafter, the current knowledge on the crosstalk between microbiota and the mucosal immune system and probiotics in application is also discussed herein, thereby providing a theoretical basis for the development of microbe-based disease control technologies in aquaculture.

中文翻译：

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共生细菌 - 免疫串扰塑造硬骨鱼的粘膜稳态

鱼的粘膜表面含有复杂且动态的微生物群。由于共生微生物群在促进生长、营养、发育、代谢和免疫反应等诸多生物学功能中发挥着至关重要的作用，因此许多学者开始将微生物群称为“扩展的自我”。多项研究表明，正常的微生物群有助于鱼类健康，微生物群落的紊乱可能导致继发感染和疾病。在进化选择力的作用下，鱼类已经发展出优良的先天免疫机制和由 B 细胞和 T 细胞组成的适应性免疫系统，以区分有益菌和机会菌以维持微生物群落的稳态。许多功能研究表明免疫细胞、细胞因子和 Igs 参与维持微生物组的稳态，许多有益微生物有助于提高抵抗外部威胁的免疫屏障。此外，许多宿主衍生的益生菌已在水产养殖领域得到经验使用，并已被证明可提供有效的鱼类疾病保护。尽管与哺乳动物相比，鱼类的微生物群与粘膜免疫系统之间的相互作用知之甚少，但管理水产养殖系统微生物群可能代表了一种有希望的替代抗生素来预防和控制疾病的方法。因此，本综述提供了对鱼类粘膜组织中当前特征的微生物组成的更新和全面的总结。此后，本文还讨论了目前关于微生物群与粘膜免疫系统和益生菌应用之间的串扰的知识，