Antagonistic activity of Kelabau fish (Osteochilus melanopleurus) gut bacteria against Aeromonas hydrophila and Pseudomonas sp.

Abstract

Abstract. The present study was conducted to isolate the kelabau fish (Osteochilus melanopleurus) gut bacteria, in order to identify and evaluate their potential for probiotics in freshwater aquaculture. A total of 19 bacterial isolates associated with O. melanopleurus gut, collected from Melintang Lake, East Kalimantan Province, Indonesia. Antibacterial activities were measured by the zone of inhibition in an antagonistic test against Aeromonas hydrophila (AH-1), A. hydrophila ATCCR 35654 TM* and Pseudomonas sp. (PS-1). Most of the extracelullar product (ECP) and intracelular product (ICP) of O. melanopleurus gut bacterial isolates demonstrated ability to prevent the growth of fish pathogens. The isolates that demonstrated high antagonistic activity were represented by isolates of BP1, BP2, BP3, BP4, BPs1, BPs2, BeP1 and BK. According to the biochemical characteristics of the eight isolates of O. melanopleurus gut from Melintang Lake East Kalimantan, revealed to be closely similar to Aeromonas sp., Plesiomonas sp., Bacillus cereus, Acinetobacter sp., Pseudomonas pseudomallei, Vibrio alginolyticus, Bacillus circulans and Vibrio sp. From this study, it can be concluded that the eight bacteria isolated from O. melanopleurus intestine, can be considered as potential candidates for probiotics development.