In this study, experiments were performed to identify and screen Streptomyces strains that are antagonistic to Aeromonas hydrophila, which causes hemorrhagic disease in fishes. Among 80 isolates, 3 strains capable of antagonizing Aeromonas hydrophila by the agar diffusion plate method were obtained. | Vietnam Journal of Agricultural Sciences ISSN 2588-1299 VJAS 2018; 1(1): 52-59 Characterization and Identification of a Streptomyces Strain with Biocontrol Activity against Aeromonas Hydrophila Causing Haemorrhage Disease in Fish Nguyen Xuan Canh, Dinh Thi Thom, and Nguyen Thanh Huyen Faculty of Biotechnology, Vietnam National University of Agriculture, Hanoi 131000, Vietnam Abstract In this study, experiments were performed to identify and screen Streptomyces strains that are antagonistic to Aeromonas hydrophila, which causes hemorrhagic disease in fishes. Among 80 isolates, 3 strains capable of antagonizing Aeromonas hydrophila by the agar diffusion plate method were obtained. The strain numbered 1083 had a strong activity with a 25 mm diameter clear zone of bacteria. This strain showed grey colonies after 7 days of incubation. After 7 days of incubation, the grey colonies had white borders, produced soluble pigments on the medium, grew well at 30°C and neutral pH, and adapted well to medium containing a high salt concentration. Strain 1083 was able to utilize different sources of carbon and nitrogen. Sequence analysis of 16S rRNA showed that strain 1083 had a similarity of 99% compared to Streptomyces antibioticus. Based on morphological, physiological, and biochemical characteristics, as well as molecular biological analysis, strain 1083 was identified as Streptomyces antibioticus. Keywords Fish, Sequence analysis, 16S rRNA, Aeromonas hydrophila, Streptomyces sp Introduction Received: July 26, 2017 Accepted: April 18, 2018 Correspondence to nxcanh@ ORCID Xuan Canh Nguyen Aquaculture industries around the world have been decimated by epidemics of a hypervirulent pathotype of Aeromonas hydrophila (Al-Fatlawy and Al-Hadrawy, 2014; Julia and Phillip, 2012). A. hydrophila is ubiquitous in warm-water environments and has a diverse host range .
