Abstract
Schizochytrium sp. added to the diet is beneficial to improve growth and fatty acid profile of fish, but there is a lack of comprehensive understanding of the mechanism by which Schizochytrium sp. supplementation produces pathogen resistance. In the present study, the effects of dietary Schizochytrium sp. on the metabolic and intestinal microbial responses, and the intestinal histological structure were investigated in zebrafish. Three experimental diets containing different concentrations of Schizochytrium sp. (0, 60, and 120 g/kg, respectively) were formulated to feed zebrafish for 56 days. The challenge trial with the fish pathogen (Edwardsiella piscicida) showed that a diet with 120 g/kg Schizochytrium sp. significantly increased the survival rate of zebrafish. Additionally, the highest goblet cell density in the intestinal wall was observed in zebrafish fed with 120 g/kg Schizochytrium sp. Metabolomic analysis of humoral fluids indicated that the diet supplemented with Schizochytrium sp. boosted the TCA cycle, energy supply, taurine metabolism, and L-serine metabolism, whereas cholesterol metabolism decreased in zebrafish. The microbiome analysis revealed that a 120 g/kg Schizochytrium sp. supplemented diet could remarkably increase the abundance of beneficial bacteria (i.e., Lactobacillus, Dorea, Butyricicoccus, and Pseudoxanthomonas), and reduce several potential pathogens (i.e., Flavobacterium, Pseudomonas, Citrobacter, and Mycoplasmas). Combined omics analysis indicated that Dorea and Butyricicoccus species were related to the disease resistance in fish. The results of dual-omics analysis also revealed that Schizochytrium sp. had the potential to improve some metabolism related to immune function and intestinal health, thus enhancing the disease resistance of zebrafish. Our research provides a novel insight into the effect of microalgae on disease resistance in aquatic animals. Moreover, this investigation sheds substantial light on immune system processes in zebrafish and identifies candidate probiotic bacteria with immunomodulatory properties.
Highlights
As an essential nutrient for farmed fish, the fish oil from wild fish has been partly replaced by vegetable ingredients to prevent overfishing
The microbiome analysis revealed that a 120 g/kg Schizochytrium sp. supplemented diet could remarkably increase the abundance of beneficial bacteria (i.e., Lactobacillus, Dorea, Butyricicoccus, and Pseudoxanthomonas), and reduce several potential pathogens (i.e., Flavobacterium, Pseudomonas, Citrobacter, and Mycoplasmas)
Dietary supplement of Schizochytrium sp. could improve the survival rate of zebrafish when infected with Edwardsiella piscicida
Summary
As an essential nutrient for farmed fish, the fish oil from wild fish has been partly replaced by vegetable ingredients to prevent overfishing. Schizochytrium sp., a type of marine microalgae, is considered as a promising alternative to fish oil for improving growth and fatty acid profile in fish. There lacks a comprehensive understanding of disease resistance on microalgae supplementation of fish. To understand the pathogen-resistant mechanisms of diets enriched with microalgae, the effects of dietary Schizochytrium sp. On the intestine microbial and metabolic profile of zebrafish were investigated To understand the pathogen-resistant mechanisms of diets enriched with microalgae, the effects of dietary Schizochytrium sp. on the intestine microbial and metabolic profile of zebrafish were investigated
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