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Browsing by Author "Silva, Ana Catarina Marcelino Costa"

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  • Effect of salinity and feed sterilization in interactions between gut and water microbial communities in Nile tilapia (Oreochromis niloticus) larvae
    Publication . Silva, Ana Catarina Marcelino Costa; Verreth, Johan; Verdegem, Marc; Giatsis, Christos
    Some tilapia species, including Oreochromis niloticus, are good candidates for brackish water culture due to salinity tolerance and good growth performances. In this report, the effect of salinity on the bacterial dominance in fish gut, as well as their relation with water and feed microbial communities, were tested. The effect of a regular diet versus a sterile diet on the microbial community composition in the fish gut was also evaluated. This resulted in 4 treatments, randomly assigned to 12 aquaria active suspension systems. The experiment was had the duration of 42 days, from the moment of first feeding. The effects of these two factors (salinity (fresh water and salt water) and feed sterilization (non-sterile feed and sterile feed)) on the microbial composition in water and fish guts were evaluated in a 2x2 factorial design. Ten fish guts per aquaria and 1 water sample per aquarium were sampled on days 0, 7, 14, 28 and 42. Bacterial DNA was extracted and amplified by Polymerase Chain Reaction. Bacterial DNA profiles were obtained through Denaturing Gradient Gel Electrophoresis. All the samples were clustered based on band position and intensity (Pearson correlation) and the similarity values among sample profiles were obtained. The gut microbial communities were different between fishes from fresh and salt water systems on day 7 (88.2±9.52% vs 63.7±28.14%) and 28 (76.9±8.28% vs 70.2±17.58%). A significant increase of similarity between system water bacterial communities and fish gut over the different sampling days was observed. Feed also had a significant increase of similarity with fish gut over time, starting with 0.4±10.2% for fresh water and 3.5±2.94% for salt water, and ending with a significantly higher value of 21.7±11.09% for fresh water and 30.4±14.12% for salt water. On the other hand, feed sterilization presented significant differences in all sampling days between fresh and saltwater bacteria populations. However, gut microbiota from fish fed with sterile feed suffered less the effect of water and feed than the fish fed with regular feed. Clearly, this study is a starting point for the complete understanding of how microbial communities are established and what the goals of future research should be.
    2010Master thesis Open access Show more