LAUSR

This study aimed at assessing the effect of short-chain fructooligosaccharides (scFOS), xylooligosaccharides (XOS), and galactooligosaccharides (GOS) on European sea bass juveniles gut microbiota. Four practical diets were formulated with fish meal (FM) and plant feedstuffs (PF) as protein sources (circa 30:70 of protein from FM:PF) and to include 1% of α-cellulose (control diet, CTR), or 1% of scFOS, XOS, or GOS (diets FOS, XOS, and GOS, respectively). Triplicate groups of fish with 79 g were fed with the experimental diets during 30 days. Gut content was sampled at days 7 and 30 for allochthonous microbiota characterization. Lactobacillus, Pseudomonas, Vibrio, and Burkholderia were the main genera found in fish gut. Gut allochthonous microbiota presented an increased number of operational taxonomic units (OTUs) and a higher Margalef index of bacterial richness in fish fed scFOS and XOS. Gut allochthonous microbial OTUs, Margalef species richness index, Shannon’s diversity index, and SIMPER similarity were unaffected by sampling day. In conclusion, scFOS and XOS modulated European sea bass gut microbial community and this effect persisted throughout time. These changes in gut microbiota composition contribute to explain the positive effects on growth performance, immune status, and lipid and glucose metabolism previously reported in European sea bass fed with scFOS and XOS.