Key Laboratory of Aquatic Animal Immune Technology, Guangdong Province, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, 510380, China.
Key Laboratory of Fishery Drug Development, Ministry of Agriculture and Rural Affairs, Pearl River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou, 510380, China.
Appl Microbiol Biotechnol. 2019 Nov;103(21-22):9023-9035. doi: 10.1007/s00253-019-10176-8. Epub 2019 Oct 25.
Streptococcus agalactiae is a major pathogen causing streptococcosis. To prevent and control this bacterial disease, antagonistic bacteria have become a new research hotspot. This study evaluated the probiotic potential of Bacillus velezensis LF01 strain, which is antagonistic to S. agalactiae. The active compounds produced by LF01 showed antimicrobial activity against a broad spectrum of fish pathogens, including S. agalactiae, Streptococcus iniae, Aeromonas hydrophila, Edwardsiella tarda, Edwardsiella ictaluri, Aeromonas schubertii, Aeromonas veronii, Aeromonas jandaei, and Vibrio harveyi. The antimicrobial compounds were heat stable, pH stable, UV stable, resistant to proteases, and could be stored for a long time. To evaluate the probiotic function of LF01 in Nile tilapia, juveniles were divided into three treatment groups: a control group, an interval feeding group, and a continuous feeding group. Tilapia fed with LF01-supplemented diets (1.0 × 10 CFU/g) showed significantly better growth performances than those of the control group (P < 0.05). Tilapia fed with LF01-supplemented diets significantly increased lysozyme (LZY) and superoxide dismutase (SOD) activities. The expression of three immune-related genes (C3, lyzc, and MHC-IIβ) was higher in the intestine, head kidney, and gill of tilapia from the continuous feeding group than in those from the control group (P < 0.05). Tilapia fed with LF01-supplemented diets showed remarkably improved survival rates after S. agalactiae infection, and analysis of their intestinal tract pathogens revealed that the abundance of Edwardsiella and Plesiomonas had significantly decreased compared with the control group. Our findings demonstrate that LF01 is an effective antagonist against various fish pathogens and has potential for controlling infections by Streptococcus spp. and other pathogens in tilapia.
无乳链球菌是引起链球菌病的主要病原体。为了预防和控制这种细菌性疾病，拮抗菌已成为一个新的研究热点。本研究评估了对无乳链球菌具有拮抗作用的解淀粉芽孢杆菌 LF01 菌株的益生菌潜力。LF01 产生的活性化合物对包括无乳链球菌、海豚链球菌、嗜水气单胞菌、迟缓爱德华菌、维氏气单胞菌、舒伯特气单胞菌、维罗纳气单胞菌、简达气单胞菌和哈维氏弧菌在内的多种鱼类病原体具有广谱抗菌活性。抗菌化合物具有热稳定性、pH 稳定性、耐 UV 性、抗蛋白酶性，并能长期储存。为了评估 LF01 在尼罗罗非鱼中的益生菌功能，将幼鱼分为对照组、间隔投喂组和连续投喂组三个处理组。投喂 LF01 补充饲料（1.0×10 CFU/g）的罗非鱼的生长性能明显优于对照组（P<0.05）。投喂 LF01 补充饲料的罗非鱼的溶菌酶（LZY）和超氧化物歧化酶（SOD）活性显著提高。连续投喂组罗非鱼肠道、头肾和鳃中三种免疫相关基因（C3、lyzc 和 MHC-IIβ）的表达均高于对照组（P<0.05）。投喂 LF01 补充饲料的罗非鱼在无乳链球菌感染后存活率显著提高，分析其肠道病原体发现，与对照组相比，爱德华氏菌和假单胞菌的丰度显著降低。本研究结果表明 LF01 是一种有效的鱼类病原体拮抗剂，具有控制罗非鱼链球菌和其他病原体感染的潜力。
