Screening of Lactic Acid Bacteria from Freshwater Fish Intestines and Their Effects on Growth, Immunity, and Disease Resistance in Zebrafish

Abstract

This study aims to isolate the freshwater fish–derived potential probiotics and evaluate their beneficial effects on the growth, immune response, and disease resistance of juvenile zebrafish (Danio rerio). Herein, three strains (Leuconostoc mesenteroides GL-5, Weissella hellenica GJ-1, and Pediococcus claussenii GJ-3) were identified with antagonistic activity against fish pathogens, high tolerance to 0.1% bile salt, and good hydrophobicity. As the model, zebrafish (15days post-fertilization, dpf) were fed with a basal diet (control) supplemented with GL-5, GJ-1, GJ-3, heat-killed Leuconostoc mesenteroides GL-5*, and commercial probiotics (positive control) at a concentration of 1,\texttimes,107CFU/mL for 4weeks. Compared with the GL-5* (36.35,\textpm,2.03mg fish-1) and control (37.31,\textpm,1.91mg fish-1) groups, the GL-5 (58.15,\textpm,2.58mg fish-1), GJ-1 (69.55,\textpm,3.85mg fish-1), GJ-3 (62.90,\textpm,2.99mg fish-1), and commercial probiotic (62.03,\textpm,2.68mg fish-1) treatment were found to significantly promote the growth of zebrafish. Compared to the control group challenged by immersion with 1,\texttimes,107CFU/mL Aeromonas hydrophila, the GJ-3 and positive groups showed the highest transcript levels of IL-1$\beta$ and TNF-$\alpha$ at 8h post-challenge (P,$<$,0.05). The survival rates (80%) of the GJ-3 and commercial probiotic–fed groups were significantly higher than that of the control group (50%) at 32h post-challenge (P,$<$,0.05). Therefore, Pediococcus claussenii GJ-3 can be considered a potential probiotic for reducing the use of antibiotics and preventing bacterial diseases in fish.

Zhenjiang Zech Xu

Professor

My research interests include microbiome, (meta)genomics and machine learning.