Abstract: Vibrio harveyi is a main pathogenic bacterium that can induce vibriosis of shrimp and fish in the marine environment, causing huge economic losses in aquaculture. In this paper, 49 strains of lactic acid bacteria (LAB) were isolated from the marine fish intestine by the use of 1.0% CaCO3 MRS agar, including seabass, coilia ectenes, Paralichthys lethostigma and turbot. strain YP4-5 isolated from the intestine of Paralichthys lethostigma had strong antagonistic activity against V. harveyi using the method of Oxford cup agar diffusion, showing an inhibitory zone diameter of 18.26 mm. Antimicrobial substances of the cell-free supernatant (CFS) produced by strain YP4-5 were sensitive to protease, heat stable and effective within the pH range of 2.5–4.5, and they were preliminary determined as bacteriocins. The growth curve indicated that 74.74% of V. harveyi was inhibited by treatment with the CFS at a concentration of 0.4 MIC. Furthermore, cell integrity damage, cell membrane dissolution and intracellular component leakage were observed by scanning electron microscope. Strain YP4-5 was identified as Lactobacillus sakei according to physiological and biochemical characteristics and 16S rRNA sequence analysis. This research can provide a good source of probiotics to prevent and control V. harveyi infection in aquaculture.

Key words: marine fish intestine, lactic acid bacteria, inhibition, Vibrio harveyi, screening and identification