Effects of the Microbiome Manipulation on Biological Performances of Zebrafish (Danio rerio) Embryos and Larvae

Abstract

Growth and development of organisms with good health would be essential in increasing productivity in aquaculture. One of the main links to high animal productivity is the microbial diversity in with the aquatic community. If the microbiome is healthy with a balance between harmful and beneficial bacteria it is able to provide many advantages to the growth of aquaculture. Zebrafish larvae were reared in the presence of 1) a probiotic containing 17 strains of Lactobacillus spp., 2) an amoxycillin solution or 3) water from the brood stock culture tank as the control and developmental parameters were monitored until 10 days post fertilization. Bacteria present in the larvae were cultured and identified by sequencing the V4 hypervariable region of the bacterial 16s rRNA. Ammonia tolerances of larvae were assessed but did not vary significantly. Probiotic treated larvae showed significant increase of every morphological parameter and highest survival compared to those treated with antibiotics (P<0.001). However, controls performed comparably to the probiotic-treated larvae. DASPEI staining revealed fluorescence indicating that probiotic treated larvae had accelerated gut development and initial function. Microbial analysis revealed an abundance of bacteria in the probiotic treatment, and the species identified were Pseudomonas spp. and Aeromonas spp. (Proteobacteria). The second most diverse microbiome was seen in controls and the least in the antibiotic treatment. In these also proteobacteria were found but in the antibiotic a pathogenic bacterium was identified (Strenotrophomonas maltophilia). This may reflect an unbalanced microbiome. According to these results the presence of Lactobacillus spp. and high abundance of other bacteria favorably influenced the growth of larvae and organ development with enhanced intestinal digestive function.