The study of the composition of the gilthead sea bream gut microbiome is becoming a relevant item in the “omics” technological offer of the IATS-CSIC infrastructure (Spain). Four AQUAEXCEL2020 Transnational Access (TNA) projects took advantage of this platform for the evaluation of the effects of probiotics, feed additives and alternative protein sources in aquaculture feeds. These fruitful collaborations have resulted in four Open Access publications in two special issues of Frontiers in Marine Science and Frontiers in Physiology, see information below.


PhD student Federico Moroni (University of Insubria, Italy) conducted a feeding trial with diets supplemented with probiotic Lactococcus lactis (LABFORTIFEEDBREAM project). After a 12-week trial, it was found that feed efficiency was not improved by the probiotic supplementation, though the final body weight of fish fed the highest dose of the probiotic (5×109 CFU/kg) was higher than in fish fed the control diet. The probiotic supplementation did not alter the morphology nor promoted the host colonization of gut microbiota, but induced changes in the mucosal adherent microbiota with a higher Firmicutes/Bacteroidetes ratio than control fish. This feature is related to lean body mass in different animal models, so this could be correlated to their better growth performance. His work can be accessed at Frontiers in Marine Science 8:659519.


Paula Solé-Jiménez (LSAqua, Belgium) aimed to unravel the effects of partial and total replacement of fish meal by a commercial protein source (LSAqua SusPro) made of bacterial single cell proteins and processed animal proteins (PAPs)(BREAMREPLACER project). Growth rates of juvenile fish fed with the partial replacement of fish meal with LSAqua SusPro were indistinguishable from the control group, and only a slight impairment was found with the total replacement of fish meal. This drawback effect was related to a non-pathologic but prevailing pro-inflammatory gut condition. However, metagenome pathway analysis highlighted that the reshaping of the adherent mucosal microbiota would contribute to counter-regulate the intestinal pro-inflammatory condition induced by the tested LSAqua diets. Her work and results can be accessed at Frontiers in Marine Science 8: 705041 (2021).


Prof. Giulia A. Wiggers (Pampa Federal University, Brazil) analyzed the potential benefits of dietary egg white hydrolysate (EWH) supplementation in gilthead sea bream juveniles fed plant-based diets (EGGPEPFISH project). After an 8-week feeding trial, EWH supplementation ameliorated the goblet cell depletion and the hepatic and intestinal lipid accumulation induced by the replacement of fish meal and fish oil with plant ingredients. EWH also modified the composition of gut microbiota at the low taxonomic level, being related the overabundance of the genus Propionibacterium to the increased concentration of intestinal propionate. Such microbial production was also related to the inhibition of feed intake via its antagonism with cholesterol metabolism, as evidenced by the underrepresentation of bile acids synthesis and steroid degradation in the inferred metagenome of EWH fish. These findings suggest that this functional food ingredient might act as an anti-obesogenic factor with a potential role in finishing diets for tuning fillet fatty acid composition of marketable fish. More details of her work at Frontiers in Marine Science 8:698484.


Dr Gabriella do Vale Pereira (SPAROS Lda, Portugal) addressed the main effects of new feed formulations based on increased circularity and resource utilization on the composition of mucosal adherent bacteria from gilthead sea bream anterior intestine, in association with changes in the host  transcriptomic patterns of intestine, liver and head kidney (MAS_BREAM Project). Data on growth performance highlighted that different fish feeds formulations based on PAPs, insect meal, yeast and microbial biomasses can be used with high success for growing gilthead sea bream juveniles. Furthermore, the correlation of microbiome and host gene expression at the local and systemic level offers new insights into the physiological processes promoting both metabolic and gut homeostasis and, ultimately, the health of farmed fish. This reinforces the action of the gut microbiome as a “second genome”, being involved in –and/or being influenced by– the regulation of the transcriptomic response in fish fed new fish feed formulations. Her work can be found at Frontiers in Physiology 12:748265.

The IATS-CSIC microbiome platform has shown to be a reliable approach for assessment of fish health and welfare in a wide range of experimental models and processes of interest for potential AQUAEXCEL3.0 TNA users.