School of Biosciences, Mahatma Gandhi University, Priyadarshini Hills, Kottayam, Kerala, India.
Department of Animal Science, Central University of Kerala, Kanhangad, Kerala, India.
Microb Pathog. 2017 Dec;113:403-411. doi: 10.1016/j.micpath.2017.11.019. Epub 2017 Nov 14.
Microbial fish pathogens are prevalent in aquaculture. Control of bacterial fish pathogens is important and bio control of pathogenic bacteria is a novel field of study. The aim of this study was to evaluate the antagonistic activity of bacteria isolated from Anabas testudineus against potent fish pathogens. The cellular components/preparations and filtered cell free culture supernatants were effective against six fish pathogens. Altogether 110 strains were isolated from fish proximal and distal intestine, out of which 10 strains were selected through well diffusion method. From them a strain HGA4C having prominent antimicrobial activity was selected as candidate probiotic strain. The whole-cell product, heat-killed whole-cell product and the filtered broth were exhibited bactericidal activity against the tested pathogens. Among them cell free culture supernatant showed maximum inhibition. In addition, isolated candidate probiotic bacterium was capable of producing extracellular enzymes important for the digestion of food ingredients and was effectively grown in fish mucus obtained from Oreochromis niloticus. The strain tolerated gradient of bile juice secreted by the host and effectively produced biofilm. Analysis of 16S rDNA sequence revealed that isolated strain HGA4C was Paenibacillus polymyxa (MF457398.1). Furthermore intraperitoneal injection of the bacterium did not induce any pathological anomalies or mortalities in Oreochromis niloticus and disclosed the safety of this bacterium as a candidate probiotic in aquaculture.
水产养殖中普遍存在微生物鱼类病原体。控制细菌鱼类病原体非常重要，而对病原菌的生物防治是一个新的研究领域。本研究旨在评估从攀鲈中分离的细菌对强致病性鱼类病原体的拮抗活性。细胞成分/制剂和过滤的无细胞培养上清液对 6 种鱼类病原体有效。从鱼类近端和远端肠道共分离出 110 株细菌，其中 10 株通过孔扩散法进行了选择。从中选择了具有显著抗菌活性的菌株 HGA4C 作为候选益生菌菌株。全细胞产物、热灭活全细胞产物和过滤培养液对测试的病原体均表现出杀菌活性。其中无细胞培养上清液显示出最大的抑制作用。此外，分离出的候选益生菌菌株能够产生对食物成分消化很重要的胞外酶，并能有效地在从尼罗罗非鱼获得的黏液中生长。该菌株能够耐受宿主分泌的胆汁梯度，并能有效地产生生物膜。16S rDNA 序列分析表明，分离出的菌株 HGA4C 为多粘类芽孢杆菌（MF457398.1）。此外，该细菌的腹腔注射不会在尼罗罗非鱼中引起任何病理异常或死亡，表明该细菌作为水产养殖中的候选益生菌是安全的。
