【摘要】 为探索尼罗罗非鱼(Oreochromis niloticus)适宜的养殖水体碱度，分析了不同初始碱度(3.90、21.57和48.88 mmol/L)养殖的尼罗罗非鱼的肝脏免疫指标、肠道微生物和肠道代谢物差异。结果显示，21.57 mmol/L碱度组尼罗罗非鱼的肝脏碱性磷酸酶(AKP)活性最高，肝脏免疫球蛋白M(IgM)和补体C3含量最高，肝脏肿瘤坏死因子α(TNFα)含量最低。48.88 mmol/L碱度组尼罗罗非鱼肝脏AKP活性、肝脏IgM和补体C3含量最低，肝脏TNF α含量最高。二元回归分析发现，养殖水体初始碱度为16.32～24.51 mmol/L时，尼罗罗非鱼的免疫性能最高。21.57 mmol/L碱度组尼罗罗非鱼肠道微生物丰富度和多样性最高。与对照组相比，21.57 mmol/L碱度组尼罗罗非鱼丙氨酸、酪氨酸和色氨酸生物合成等途径显著上调，48.88 mmol/L碱度组罗非鱼辅因子生物合成、核酸代谢、苯丙氨酸代谢等途径显著下调。本研究表明尼罗罗非鱼最适初始碱度范围为16.32～24.51 mmol/L,高碱度(48.88 mmol/L)对尼罗罗非鱼的肝脏免疫、肠道菌群结构和代谢产生负面影响。更多还原

【Abstract】 The interaction between water alkalinity and the intestinal microbiota of Oreochromis niloticus remains insufficiently explored in aquaculture research.This study investigates the effects of varying water alkalinity levels(2.36 mmol/L,3.90 mmol/L,21.57 mmol/L,and 48.88 mmol/L) on the growth and immune responses of O.niloticus.Additionally, it identifies the optimal alkalinity that enhances health and productivity in aquaculture settings.Advanced techniques such as 16S rRNA gene sequencing and metabolomics are employed to provide a detailed analysis of alkalinity′s impact on the gut microbiome′s structure and metabolic functions.This research enhances understanding of the complex relationships between water chemistry and fish physiology, offering valuable insights into the symbiotic interactions within aquaculture ecosystems.The results revealed that in the 21.57 mmol/L alkalinity group, liver alkaline phosphatase(AKP) activity was significantly elevated, along with higher levels of liver immunoglobulin M(IgM) and complement C3.Conversely, the liver tumor necrosis factor α(TNF-α) contents were notably reduced in this group.In contrast, O.niloticus in the 48.88 mmol/L alkalinity group exhibited lower AKP activity and decreased levels of IgM and C3 in the liver.Additionally, TNF-α content in the liver was found to be highest in this group.The result of the regression analysis revealed that O.niloticus exhibited optimal immune performance within an initial alkalinity range of 16.32 to 24.51 mmol/L.The gut microbiota of O.niloticus exhibited the highest richness and diversity at an initial alkalinity of 21.57 mmol/L.Modifying the alkalinity level enhanced the growth of beneficial bacteria in the tilapia gut.Additionally, the water′s alkalinity level influenced the gut metabolites and metabolic pathways of O.niloticus.Specifically, the biosynthesis pathways of alanine, tyrosine, and tryptophan were significantly upregulated in Nile tilapia cultured at an initial alkalinity of 21.57 mmol/L,while pathways related to cofactors, nucleic acid metabolism, and phenylalanine metabolism were downregulated in tilapia cultured at an initial alkalinity of 48.88 mmol/L compared to the control group.This study showed that the optimal initial alkalinity range of water in O.niloticus aquaculture was 16.32～24.51 mmol/L.The overabundant initial alkalinity of water(48.88 mmol/L) adversely affected the hepatic immunity, intestinal flora and metabolites of O.niloticus.This study offers a reference for the rational regulation of alkalinity in fish farming.更多还原