Arya Manju, Shahi Neetu, Bisht Ila, Pandey Nityanand, Mallik Sumanta Kumar
ICAR-Directorate of Coldwater Fisheries Research (ICAR-DCFR), Bhimtal, Nainital, 263 136, Uttarakhand, India.
Zoology Department, Soban Singh Jeena Campus (Kumaun University), Almora, 263601, Uttarakhand, India.
Sci Rep. 2025 May 21;15(1):17580. doi: 10.1038/s41598-025-02836-9.
The study focused on the evaluation of the probiotic potency of Bacillus velenzensis STPB10, isolated from the digestive tract of the hillstream fish Snow trout (Schizothorax richardsonii). Ten B. velezensis strains were identified through colony morphology, biochemical analysis, and 16 S rRNA methods. The representative laboratory strain STPB10, was subjected to various in vitro assessments including tolerance to pH, bile salt resistance, NaCl, temperature, biofilm, endospore formation, antibiotic susceptibility and antagonistic activity to determine its potential as a probiotic strain. B. velezensis STPB10 exhibited positive results for catalase, glucose, arginine, lysine, and endospore tests, while it yielded negative results for oxidative/fermentative, DNase, and urease tests. This test isolate was γ-hemolytic in nature and demonstrated growth across a temperature range of 15 to 35 °C. Moreover, it exhibited survival rates of 31, 39.7, 47, 63, and 75% at pH values of 2, 2.5, 3, 3.5, and 4, respectively, after 6 h of incubation. At a bile salt concentration of 0.3%, the bacterium exhibited a survivability of more than 99%. A strong biofilm production by B. velezensis STPB10 was detected in tryptone soya broth enriched with 0.45% glucose (p < 0.05). It also exhibited significantly greater adhesion to intestinal mucus (63.67%). Following exposure of the intestinal mucus to B. velezensis STPB10, the adhesion of A. hydrophila, A. veronii, (A) salmonicida and V. anguillarum to the mucus was notably reduced. It was susceptible to several antibiotics and produced an antagonistic effect against pathogenic bacteria Aeromonas salmonicida, Aeromonas veronii, Vibrio anguillarum, and Aeromonas hydrophila isolated from diseased fish. The pathogenicity of (B) velezensis STPB10 through intraperitoneal injection and immersion challenge at cell concentrations of 10 and 10 CFU mL revealed that the strain did not produce any pathogenic risk to common carp. These findings highlight the resilience and adaptability of B. velezensis STPB10 as a candidate probiotic in aquaculture.
该研究聚焦于对从山溪鱼雪鲮（Schizothorax richardsonii）消化道分离出的解淀粉芽孢杆菌STPB10的益生菌潜力进行评估。通过菌落形态、生化分析和16S rRNA方法鉴定出10株解淀粉芽孢杆菌菌株。对代表性实验室菌株STPB10进行了各种体外评估，包括对pH的耐受性、耐胆盐性、对NaCl的耐受性、温度耐受性、生物膜形成、芽孢形成、抗生素敏感性以及拮抗活性，以确定其作为益生菌菌株的潜力。解淀粉芽孢杆菌STPB10在过氧化氢酶、葡萄糖、精氨酸、赖氨酸和芽孢试验中呈阳性结果，而在氧化/发酵、DNase和脲酶试验中呈阴性结果。该测试菌株本质上为γ-溶血，在15至35°C的温度范围内均能生长。此外，在pH值分别为2、2.5、3、3.5和4的条件下孵育6小时后其存活率分别为31%、39.7%、47%、63%和75%。在胆盐浓度为0.3%时，该细菌的存活率超过99%。在富含0.45%葡萄糖的胰蛋白胨大豆肉汤中检测到解淀粉芽孢杆菌STPB10能强烈产生生物膜（p < 0.05）。它对肠黏液的黏附力也显著更强（63.67%）。将肠黏液暴露于解淀粉芽孢杆菌STPB10后，嗜水气单胞菌、维氏气单胞菌、杀鲑气单胞菌和鳗弧菌对黏液的黏附力显著降低。它对几种抗生素敏感，并对从患病鱼类中分离出的病原菌杀鲑气单胞菌、维氏气单胞菌、鳗弧菌和嗜水气单胞菌产生拮抗作用。通过腹腔注射和在细胞浓度为10⁶和10⁷ CFU/mL时进行浸泡攻毒来检测解淀粉芽孢杆菌STPB10的致病性，结果表明该菌株对鲤鱼不产生任何致病风险。这些发现突出了解淀粉芽孢杆菌STPB10作为水产养殖中候选益生菌的恢复力和适应性。
