The genus Vibrio is among the most numerous and ubiquitous of marine bacteria and commonly found as etiological agents of diseases in both vertebrates and invertebrates throughout the world. Vibrio salmonicida, a halophilic and psychrophilic (cold adapted ) marine gram-negative bacterium, the etiological agent of cold-water vibriosis (also called hemorrhagic syndrome or Hitra disease) in Atlantic salmon and cod, has been studied for some years. Still the molecular mechanisms of host invasion, host specific ity, colonization and growth (host adaptation) are largely unknown. V. salmonicida probably combines several hitherto unknown factors to combat the immune defence of the host. The project will develop fundamental knowledge of intra-pathogenic and host-pat hogen communication with V. salmonicida as a model of cold water vibrios. The knowledge enables us to apply genomic data extending from bioinformatics to functional analysis, and by this discover new targets for vaccines and pharmaceutical drugs, through network building, RNomics, structural analysis, together with state-of-the-art methods in functional genomics. By understanding the virulence factors possessed by V. salmonicida, we will be able to identify pathways of disease mechanisms useful for potent ial prevention and control of infections with cold water vibrios in future farming of marine fish species.