This study evaluated the role of probiotics in enhancing intestinal immunity and mitigating polystyrene nanoplastics (PS-NPs)-induced toxicity in grass carp (Ctenopharyngodon idella). Grass carp were fed probiotics (Bacillus subtilis, Bacillus velezensis, Lactobacillus reuteri, and Lactococcus lactis) for two weeks before being exposed to PS-NPs for five days. Probiotic pretreatment alleviated PS-NPs-induced intestinal damage, with Bacillus velezensis and Lactococcus lactis groups showing milder vacuolation and villus breakage than other groups. Probiotic-treated fish exhibited transient increases in antioxidant enzyme activities (CAT, SOD, MPO) and immune gene expression (IL-6, IL-8, IL-10, IL-1β, TNF-α, and IFN-γ2) shortly after exposure, followed by significant downregulation over time. Higher abundance of the gut dominant phylum Proteobacteria was observed in four probiotic groups exposed to PS-NPs than that in the blank control group. The Clostridium phylum showed a significant decrease in the abundance both in the LRS-PS100 and LLS-PS100 groups, while the abundance of the Thick-walled phylum increased. The Spearman correlation matrix revealed that specific gut microbiota, such as Serratia, Neisseria, and Lactococcus, were significantly associated with enzymatic activities and immune system related genes’ expressions. Probiotic pretreatment enhanced the intestinal immune response of grass carp. However, this enhanced immune response was insufficient to counteract the toxic effects of PS-NPs exposure, particularly in terms of oxidative stress levels and gut microbial diversity. This study offers new insights into the potential of probiotics to combat NPs pollution in aquaculture. It emphasizes the need for further research to explore various probiotic combinations. Future studies should also investigate optimal dosages and durations to effectively mitigate the biological toxicity of NPs pollution.

中文翻译：

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聚苯乙烯纳米塑料通过改变草鱼 （Ctenopharyngodon idella） 的肠道微生物群来隔离益生菌的毒性，减轻益生菌的潜力


本研究评估了益生菌在增强草鱼肠道免疫力和减轻聚苯乙烯纳米塑料 （PS-NPs） 诱导的草鱼 （Ctenopharyngodon idella） 毒性中的作用。草鱼被喂食益生菌（枯草芽孢杆菌、维莱森芽孢杆菌、罗伊氏乳杆菌和乳酸乳球菌）两周，然后暴露于 PS-NPs 五天。益生菌预处理减轻了 PS-NPs 诱导的肠道损伤，Bacillus velezensis 和 Lactococcus lactis 组比其他组表现出更轻微的空泡和绒毛破损。益生菌处理的鱼在暴露后不久表现出抗氧化酶活性（CAT、SOD、MPO）和免疫基因表达（IL-6、IL-8、IL-10、IL-1β、TNF-α 和 IFN-γ2）的短暂增加，随后随着时间的推移显着下调。在暴露于 PS-NPs 的四个益生菌组中观察到肠道优势门变形菌门的丰度高于空白对照组。梭状芽胞杆菌门在 LRS-PS100 和 LLS-PS100 组中的丰度均显著降低，而厚壁门的丰度增加。Spearman 相关矩阵显示，特定的肠道微生物群，如沙雷氏菌、奈瑟菌和乳球菌，与酶活性和免疫系统相关基因的表达显著相关。益生菌预处理增强了草鱼的肠道免疫反应。然而，这种增强的免疫反应不足以抵消 PS-NPs 暴露的毒性作用，特别是在氧化应激水平和肠道微生物多样性方面。这项研究为益生菌对抗水产养殖中 NPs 污染的潜力提供了新的见解。它强调需要进一步研究以探索各种益生菌组合。 未来的研究还应调查最佳剂量和持续时间，以有效减轻 NPs 污染的生物毒性。