Microbial ecology of the intestinal tract of gilthead sea bream (Sparus aurata Linneus, 1758)

The study of fish gut microflora is important because it reflects the bacterial composition of the rearing environment and the dietary regimen of ingested food; moreover these microbiota play a role in the health and the quality of adult fish. The aim of this research was to study the microbial ecology of the gut of two groups of gilthead sea bream (<i>Sparus aurata</i> L.) reared in off-shore floating cages and in lagoon, located in Sardinian coast, in order to quantify the heterotrophic bacteria and to identify at genus and species level the dominant bacterial communities of the intestinal tract by means of the ARDRA technique and sequencing of the 16S rRNA gene. This study aimed to test the microbiological quality of fish and intestinal microbial biodiversity in order to detect a possible link with the rearing system. The results showed a significantly higher bacterial load in the gilthead sea bream farmed in the lagoon than in the fish from the off-shore cages and highlighted a different bacterial qualitative composition of the gut microflora in the two groups of fish, although the presence of the <i>Pseudomonas</i> spp. was observed in all the fish studied. A greater microbial diversity at species level was observed in the sea bream reared in the lagoon.