Dietary selenium regulates the diversity and stability of microbial communities in stomach and intestine of rabbitfish (Siganus oramin)

The stability of gastrointestinal ecosystem and microbial interactions herein are critical to host health, but how to regulate gut microbiota and maintain its stability remains unclear. Macroalgae used as fish feed has economic and environmental advantages, and an extra addition of selenium (Se) may further replenish the necessary micronutrient for fish. Recent studies suggested that dietary Se could enhance fish health by regulating Se-associated enzymes. However, the effects of dietary Se on the microbial diversity and stability in fish stomach and intestine are poorly understood. Rabbitfish (Siganus oramin) fed with different contents of dietary Se enriched in macroalgae were used to investigate the effects of Se on the fish growth and gastrointestinal microbial communities. We found that the low dietary Se (∼2.51 μg/(g·dw)) could significantly enhance the growth of rabbitfish and maintain gastrointestinal ecological stability. The microbial ecological networks indicated that the low dietary Se altered the potential interactions within microbial community and increased the number of potential keystones to maintain the stability. Moreover, low dietary Se improved the microbial diversity, enhanced probiotics but reduced pathogenic bacteria in the gastrointestinal ecosystem. We also found that the microbiota in stomach was more diverse and stable than that of intestinal microbiota under the enriched Se diets. This study reveals the effects of dietary Se on fish growth and the underlying mechanism maintaining network stability in gastrointestinal ecosystem, which also broadens our understanding of dietary regulation of gastrointestinal microbiota.