Supervisors: Lone Gram (Danish Institute for Fisheries Research) and Jens Laurits Larsen (The Royal Veterinary and Agricultural University)
Bacterial diseases are major problems in the expanding aquaculture industry and antibiotics remains an important disease control measure for a number of fish and crustaceans. However, to reduce the risk of development and spread of antibiotic resistant bacteria, other, more environmentally friendly methods for control of fish diseases in aquaculture must be developed. This requires a detailed understanding of fish diseases and the purpose of this project is to develop such knowledge by studying the interaction between pathogenic bacteria, host and environmental factors. As an example, the project will determine the importance of bacterial signalling molecules (acylated homoserine lactones) for virulence of fish pathogenic bacteria and fish immune defense systems. The influence of environmental factors (other bacteria, nutrients, temperature, signalling blocking compounds) for the signalling systems will be investigated.
The project focuses on N-acylated homoserine lactones (AHL), which are signalling molecules produced by many Gram-negative bacteria. The AHL compounds allow the bacterial population to sense its own density (quorum sensing) and up-regulate specific phenotypic characteristics at a particular density. In some human and plant pathogenic bacteria, the AHL-compounds regulate the expression of important virulence factors. At the same time, AHLs may also be used as communication signals between different bacterial populations, and they may interact directly with the host; typically leading to a lowered immune response. The project will determine how widespread the production of AHL compounds is in fish pathogenic bacteria, particularly Vibrio anguillarum and if production profiles can be related to virulence. Specific blocking of the AHL-systems will be investigated using Delisea pulchra furanones.