Several reports have revealed the vital role that probiotics play in fish growth and health. However, few works are available for host gut-derived probiotics on the growth, immunity, and gut microbiota of fish, especially in hybrid grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatus) due to their isolation difficulty and functional verification. This study aimed at assessing 3 host gut-derived Bacillus species' effects on the growth, immune and antioxidant-biochemical responses, haematological parameters, intestinal morphology, immune-related gene expression, gut microbiota, and disease resistance against Vibrio harveyi in hybrid grouper. A total of 480 hybrid grouper (initial weight = 9.03 ± 0.02 g) were randomly allotted into 4 groups, namely, the group fed a basal diet without probiotic inclusion (control, B0), the group fed the basal diet with Bacillus velezensis GPSAK4 (BV), the group fed the basal diet with Bacillus subtilis GPSAK9 (BS), and the group fed the basal diet with Bacillus tequilensis GPSAK2 (BT) strains at 1.0 × 10⁹ CFU/g. After a 6-week feeding trial, the results revealed significant improvements (P < 0.05) in the growth performance, whole fish-body proximate composition, blood haematological parameters, serum, liver, and intestinal biochemical indexes, intestinal morphology, and protection against V. harveyi pathogen in the probiotic-treated groups compared with the untreated. Additionally, the expressions of intestinal tight junction genes (occludin and ZO1), pro- and anti-inflammatory genes, including IL1β, IL6, IL8, TNFα, MyD88, IL10, and TGFβ, were upregulated (P < 0.05) after Bacillus species administration. Host gut-derived Bacillus supplementation shaped the gut microbiota by significantly increasing (P < 0.05) the relative abundance of Proteobacteria, Bacteroidetes, Actinobacteria (except the BS group), Acidobacteria (except the BT group), Cyanobacteria (except the BV and BT groups), and Verrucomicrobia phyla, as well as known beneficial genera (Romboutsia, Turicibacter, Epulopiscium, Clostridium_sensu_stricto 1 and 13, Lactobacillus, and Bacillus), but significantly decreased (P < 0.05) the abundance of Firmicutes, Chloroflexi, and Fusobacteria phyla, and purported pathogenic genera (Staphylococcus and Photobacterium) compared with the control group. Collectively, the results suggest that B. velezensis GPSAK4, B. subtilis GPSAK9 (especially this strain), B. tequilensis GPSAK2 dietary supplementation at 1.0 × 10⁹ CFU/g has positive effects on the intestinal health of hybrid grouper via microbial composition modulation, thus enhancing the assimilation and absorption of nutrients to boost fish growth, immunity, and disease resistance.

几份报告揭示了益生菌在鱼类生长和健康中发挥的重要作用。然而，由于宿主肠道益生菌的分离困难和功能验证，关于鱼类生长、免疫和肠道微生物群的研究很少，尤其是杂交石斑鱼（♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatus  ）。本研究旨在评估 3 种宿主肠道芽孢杆菌对生长、免疫和抗氧化生化反应、血液学参数、肠道形态、免疫相关基因表达、肠道微生物群和哈维氏弧菌抗病性的影响在杂交石斑鱼中。将 480 尾杂交石斑鱼（初始体重 = 9.03 ± 0.02 g）随机分为 4 组，即饲喂不含益生菌的基础饲料组（对照，B0）、饲喂添加贝莱斯芽孢杆菌 GPSAK4 的基础饲料组（ BV)，该组在基础饮食中饲喂枯草芽孢杆菌GPSAK9(BS)，该组在基础饮食中饲喂1.0×10 ⁹  CFU/g的特奎伦芽孢杆菌GPSAK2(BT)菌株。经过6周的饲养试验， 鱼体生长性能、全鱼近端成分、血液学参数、血清、肝脏、肠道生化指标、肠道形态、抗病能力等方面均有显着改善（P < 0.05）。五。与未治疗组相比，益生菌治疗组中的哈维氏病原体。此外，给予芽孢杆菌后，肠道紧密连接基因（occludin和ZO1）、促炎和抗炎基因（包括IL1β、IL6、IL8、TNFα、MyD88、IL10和TGFβ）的表达上调（P  <0.05）。宿主肠道来源的芽孢杆菌补充剂通过显着增加（P < 0.05) 变形菌门、拟杆菌门、放线菌门（BS 组除外）、酸杆菌门（BT 组除外）、蓝藻门（BV 和 BT 组除外）和疣微菌门以及已知的有益属（Romboutsia、Turicibacter、Epulopiscium、Clostridium_sensu_stricto 1 和 13、Lactobacillus和Bacillus ），但与对照组相比，厚壁菌门、Chloroflexi 和 Fusobacteria 门以及所谓的致病菌属（葡萄球菌属和发光杆菌属） 的丰度显着降低（P < 0.05）。总的来说，结果表明B. _ 贝莱森斯GPSAK4, B . 枯草芽孢杆菌GPSAK9（尤其是该菌株），B . 饲料中添加1.0 × 10 ⁹  CFU/g的tequilensis GPSAK2通过调节微生物组成对杂交石斑鱼的肠道健康产生积极影响，从而增强营养物质的同化和吸收，从而促进鱼类生长、免疫力和抗病能力。