By their nature and geographical location, estuaries shape different marine habitats via freshwater and seawater interactions. Thus, fish intestinal microbiota, as mediated by estuary habitat fluctuations, are fundamentally important but rarely studied. Similarly, it is unclear how, and to what extent, water microbiota influences fish intestinal microbiota in different estuary habitats. In this study, the euryhaline fish species, Collichthys lucidus from three different habitats in the Pearl River estuary (PRE) was investigated to determine the influence of habitat fluctuation on intestinal microbiota. The three water environments selected for sample collection were very different, particularly for chlorophyll-a, suspended solid, and nutrient constituents. Using high-throughput sequencing of 16S rRNA gene amplicons, we observed that dominant microbial genera in surrounding estuary waters or fish intestines were seldom shared. The most dominant genera in water samples were Candidatus Actinomarina and HIMB11, while Bifidobacterium, Stenotrophomonas, Escherichia-Shigella and Rhodopseudomonas were more abundant in fish intestines. Fish hosts can shape fish intestinal microbiota. However, microbial exchange was also found between fish intestines and water samples. The frequency of microbial exchange between fish intestines and water samples was increased from upstream to downstream estuary points, and was influenced by changes in seawater salinity in the estuary. Finally, core intestinal microbiota from C. lucidus was analyzed, and showed that Bifidobacterium, Rhodopseudomonas, Escherichia-Shigella, Acinetobacter, and Stenotrophomonas were highly abundant. These microbiota were theoretically implicated in immune responses, nutrient metabolism, probiotics, and potential pathogen behaviors. Overall, these data highlighted the composition of C. lucidus intestinal microbiota in different habitats across the PRE.

中文翻译：

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Collichthys lucidus肠道菌群的组成及其与珠江口水域菌群的相互作用

根据其性质和地理位置，河口通过淡水和海水的相互作用形成不同的海洋栖息地。因此，由河口栖息地波动介导的鱼肠微生物群从根本上来说很重要，但很少进行研究。同样，目前尚不清楚水微生物群如何以及在多大程度上影响不同河口栖息地的鱼类肠道微生物群。在这项研究中，调查了珠江口（PRE）三种不同栖息地的淡水鱼类物种Collichthys lucidus，以确定栖息地波动对肠道菌群的影响。选择用于样本收集的三种水环境非常不同，尤其是对于叶绿素-a，悬浮固体和营养成分而言。使用16S rRNA基因扩增子的高通量测序，我们观察到周围河口水域或鱼肠中的优势微生物属很少共享。水样中最主要的属是放线假丝酵母和HIMB11，而在鱼肠中双歧杆菌，嗜麦芽单胞菌，大肠杆菌-志贺氏菌和红假单胞菌则更为丰富。鱼寄主可以塑造鱼的肠道菌群。但是，在鱼肠和水样之间也发现了微生物交换。鱼肠和水样之间的微生物交换频率从上游到下游河口点增加，并且受河口海水盐度变化的影响。最后，分析了来自C.lucidus的核心肠道菌群，并显示双歧杆菌，红假单胞菌，大肠埃希菌-志贺氏菌，不动杆菌和嗜单核嗜单胞菌高度丰富。从理论上讲，这些微生物群与免疫反应，营养代谢，益生菌和潜在的病原体行为有关。总体而言，这些数据突显了PRE各地不同生境中的C. lucidus肠道菌群的组成。