Vibrio sp 33 a potential bacterial antagonist of Vibrio splendidus pathogenic to sea cucumber (Apostichopus japonicus)

Recently, the use of probiotics as an alternative strategy to control bacterial diseases in aquaculture has garnered much attention due to the merits of environmental friendliness. In this study, a bacterium identified as Vibrio sp. V33 was isolated from healthy sepia and was determined to have strong antagonistic activity towards the pathogenic isolate Vibrio splendidus Vs using the disk diffusion method. The antagonistic substance was secreted into the supernatant and was thermo-stable. The antagonistic activity of Vibrio sp. V33 may be attributed to its higher ability to compete for iron than that of V. splendidus Vs, as deduced from siderophore quantification using the CAS method. Number of colony counts from seawater and Apostichopus japonicus infection experiments showed that Vibrio sp. V33 significantly decreased the quantity of V. splendidus Vs in natural seawater and promoted the survival rate of A. japonicus infected by V. splendidus, with a relative percentage survival of 43% under the current conditions. Our findings suggest that V33 could be potentially used as potential bacterial antagonist for controlling V. splendidus infections in sea cucumber aquaculture. Statement of relevance: It might protect A. japonicus from V. splendidus infection. (C) 2016 Elsevier B.V. All rights reserved.