Project description:Most of our knowledge regarding the biodiversity of gut microbes comes from terrestrial organisms or marine species of economic value, with less emphasis on ecologically important species. Here we investigate the bacterial composition associated with the gut of Siganus fuscescens, a rabbitfish that plays an important ecological role in coastal ecosystems by consuming seaweeds. Members of Firmicutes, Bacteroidetes and delta-Proteobacteria were among the dominant taxa across samples taken from the contents and the walls (sites) of the midgut and hindgut (location). Despite the high variability among individual fish, we observed statistically significant differences in beta-diversity between gut sites and gut locations. Some bacterial taxa low in abundance in the midgut content (e.g., Desulfovibrio) were found in greater abundances on the midgut wall and within the hindgut, suggesting that the gut may select for specific groups of environmental and/or food-associated microorganisms. In contrast, some distinct taxa present in the midgut content (e.g., Synechococcus) were noticeably reduced in the midgut wall and hindgut, and are thus likely to be representative of transient microbiota. This is the first assessment of the bacterial diversity associated with the gut of S. fuscescens and highlights the need to consider the variability across different gut locations and sites when analyzing fish gut microbiomes.
Project description:Unintentional use of mold-infested plant-based feed ingredients are sources of mycotoxins in fish feeds. The presence of the emerging mycotoxins ENNB and BEA in Norwegian commercial fish feeds and plant-based feed ingredients has raised concerns regarding the health effects on farmed Atlantic salmon (Salmon salar). Atlantic salmon pre-smolts were exposed to a non-lethal single-dose of BEA and ENNB, and total RNA sequencing of the intestine and liver was carried out to evaluate gut health and identify possible hepatological changes after a single-dose dietary exposure. ENNB and BEA did not give acute toxicity, however ENNB caused the onset of pathways linked to acute intestinal inflammation and BEA exposures caused the onset of hepatic hematological disruption. The prevalence and concentration of ENNB found in today's commercial feed could affect the fish health if consumed over a longer time-period.
Project description:We recently demonstrated that dietary supplementation with seaweed leads to dramatic improvements in immune responses in S. fuscescens, a candidate species for aquaculture development in Asia. Here, to assess whether the immunostimulatory effect was facilitated by changes to the gut microbiome, we investigated the effects of those same seaweed species and four commercial feed supplements currently used in aquaculture on the bacterial communities in the hindgut of the fish. Since we found no correlations between the relative abundance of any particular taxa and the fish enhanced innate immune responses, we hypothesised that S. fuscescens might have a core microbiome that is robust to dietary manipulation. Two recently published studies describing the bacteria within the hindgut of S. fuscescens provided an opportunity to test this hypothesis and to compare our samples to those from geographically distinct populations. We found that, although hindgut bacterial communities were clearly and significantly distinguishable between studies and populations, a substantial proportion (55 of 174 taxa) were consistently detected across all populations. Our data suggest that the importance of gut microbiota to animal health and the extent to which they can be influenced by dietary manipulations might be species-specific or related to an animals' trophic level.