Role of bacterial quorum sensing and micro-algae in fish and crustacean larviculture
Bacterial disease is one of the major problems in aquaculture. Pathogenic bacteria such as V. harveyi and Aeromonas spp. infect various host species. Antibiotics remain by far the easiest and fastest solution to cure bacterial disease. However, the overuse of antibiotics has lead to resistant bacter...
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| Other Authors: | , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
Ghent University. Faculty of Bioscience Engineering
2011
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| Online Access: | https://biblio.ugent.be/publication/2057516 http://hdl.handle.net/1854/LU-2057516 https://biblio.ugent.be/publication/2057516/file/2057525 |
| Summary: | Bacterial disease is one of the major problems in aquaculture. Pathogenic bacteria such as V. harveyi and Aeromonas spp. infect various host species. Antibiotics remain by far the easiest and fastest solution to cure bacterial disease. However, the overuse of antibiotics has lead to resistant bacteria, causing the problem to become even more severe. As a result, antibiotics are not able anymore to cure infections in many cases. In this work, disruption of bacterial communication or quorum sensing (QS) is investigated as a novel approach to control bacterial infections in aquaculture. The first part of the research studied the effects of V. harveyi quorum sensing on virulence factor regulation and the impact of quorum sensing disruption on the virulence of V. harveyi and Aeromonas spp. towards giant river prawn (M. rosenbergii) and burbot (Lota lota) larvae, respectively. It was shown that QS negatively regulates the production of phospholipase, while caseinase and gelatinase are positively regulated. Meanwhile, hemolysin and lipase were found to be independent of QS. Furthermore, HAI-1 and AI-2 quorum sensing were found to be important for the virulence of V. harveyi towards prawn larvae. The CAI-1 system, on the other hand, had no effect on virulence of the bacterium in this host system. Similarly, AHL quorum sensing regulates the virulence of A. hydrophila towards burbot larvae. Meanwhile, QS antagonists (Ntetradecanoyl-L-homoserine lactone and cinnamaldehyde) protected burbot from A. salmonicida. In the second part of the research, the ability of micro-algae to interfere with QS was investigated through screening the effect of algal extracts on different bacterial QS reporter strains, including V. harveyi. The screening results showed that extracts from different micro-algal strains were able to interfere with QS regulated gene expression in the reporter strains. The interference activities were dependent on the QS signal type (unsubstituted, oxo-substituted and hydroxyl-substituted). The most interesting ... |
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