Solea senegalensis Bacterial Intestinal Microbiota Is Affected by Low Dietary Inclusion of Ulva ohnoi

Abstract

The inclusion of macroalgae in the diets of farmed fish offers the opportunity for an added-value dietary ingredient to the nutraceutical feed. The composition of algae varies greatly among species. Several <i>Ulva</i> species have been considered in aquafeed formulations for different farmed fish, and <i>Ulva ohnoi</i> is being applied recently. However, the effects of seaweed dietary inclusion on the host must be evaluated. Considering the important role of the host intestinal microbiota, the potential effects of <i>U. ohnoi</i> dietary inclusion need to be studied. In this study, the characterization of the intestinal microbiome of <i>Solea senegalensis</i>, a flatfish with high potential for aquaculture in South Europe, receiving <i>U. ohnoi</i> (5%)-supplemented diet for 90 days has been carried out. In addition, the functional profiles of bacterial communities have been determined by using PICRUSt, a computational approach to predict the functional composition of a metagenome by using marker gene data and a database of reference genomes. The results show that long-term dietary administration of <i>U. ohnoi</i> (5%)-supplemented feed modulates <i>S. senegalensis</i> intestinal microbiota, especially in the posterior intestinal section. Increased relative abundance of <i>Vibrio</i> jointly with decreased <i>Stenotrophomonas</i> genus has been detected in fish receiving <i>Ulva</i> diet compared to control-fed fish. The influence of the diet on the intestinal functionality of <i>S. senegalensis</i> has been studied for the first time. Changes in bacterial composition were accompanied by differences in predicted microbiota functionality. Increased abundance of predicted genes involved in xenobiotic biodegradation and metabolism were observed in the microbiota when <i>U. ohnoi</i> diet was used. On the contrary, predicted percentages of genes associated to penicillin and cephalosporin biosynthesis as well as beta-lactam resistance were reduced after feeding with <i>Ulva</i> diet.