Microcystin-LR (MC-LR) is regarded as one of the most toxic microcystins (MCs) isoforms. Microcystins could cause multiple organs dysfunction, and more attention has been drawn to the toxic effects on the gastrointestinal disorder. By using ex vivo everted gut sac model in 6 fish (Carassius auratus, Megalobrama amblycephala, Hypophthalmichthys molitrix, Aristichthys nobilis, Ctenopharyngodon idellus and Cyprinus carpio) and determining the accumulation of MC-LR in zebrafish intestine, we found a dose-dependent manner in the absorption and accumulation of MC-LR. Until now, little studies have been reported concerning the gut microbiota composition caused by different MC-LR exposure. The present study is the first time characterized the phylogenetic composition and taxonomic of the bacterial communities growth in the intestines of zebrafish treated with MC-LR using 16S rRNA pyrosequencing. After 30 days of treatment with 0, 1, 5 or 20 μg/L MC-LR, the alpha and beta diversity did not generate significant differences, indicating the existence of a core microbiota. However, db-RDA analysis showed that treatment with 20 μg/L MC-LR changed the characteristics of high abundances microbiota. The expression of Oatp2b1, stress related enzyme activities in gut and their associations with gut microbiota were also determined. The identified phylotypes including Actinobacteria, Lactobacillus and some opportunistic pathogens highlight the increasing risks of pathogen invasion and recovery tendency via potential probiotics resistance in zebrafish exposed to MC-LR.

微囊藻毒素-LR（MC-LR）被认为是毒性最强的微囊藻毒素（MCs）异构体之一。微囊藻毒素可能会导致多器官功能障碍，因此人们对胃肠道疾病的毒性作用引起了更多关注。通过使用离体外翻肠囊模型在6条鱼中（Car鱼，Mega鱼、,鱼、,鱼、,鱼和鲤鱼））并确定斑马鱼肠中MC-LR的积累，我们发现MC-LR的吸收和积累呈剂量依赖性。到目前为止，关于由不同的MC-LR暴露引起的肠道菌群组成的研究很少。本研究是首次使用16S rRNA焦磷酸测序技术对斑马鱼肠道中细菌群落的系统发育组成和分类进行了表征。用0、1、5或20μg/ L MC-LR处理30天后，α和β多样性没有产生显着差异，表明存在核心菌群。但是，db-RDA分析表明，用20μg/ L MC-LR处理会改变高丰度菌群的特征。Oatp2b1的表达，还确定了肠道中与应激相关的酶活性及其与肠道菌群的关系。确定的系统型包括放线杆菌，乳杆菌和一些机会性病原体通过暴露于MC-LR的斑马鱼中潜在的益生菌抗性突出了病原体入侵和恢复趋势的风险增加。