The project will perform a structure/function study at an atomic level where protein targets will be selected from the extremophilic ("being able to survive under extreme conditions") bacterias Deinococcus radiodurans and Vibrio salmonicida. The target se lection will be mainly based on results from the ongoing search for virulence factors from V. salmonicida, but also on homologous proteins from D. radiodurans when advantageous. The main objective of the project is to perform an in-depth study of proteins essential for proliferation and virulence of V. salmonicida. The selected proteins will be produced using recombinant techniques and in quantities required for structural and functional studies. The homologous proteins from the two organisms will be subj ected to a biochemical and structural comparative study in order to highlight structural and functional features. A crucial aspect of the project is to benefit from a two-way exchange of personnel, techniques, ideas and general expertise between the Norwe gian Structural Biology Centre (NorStruct) and the Macromolecular Crystallography (MX) Group at the European Synchrotron Radiation Facility (ESRF). The rather unique competence of the MX group at the ESRF in data collection and structure determination on novel proteins will be an asset to NorStruct. In addition, the MX group is facing similar tasks as NorStruct in that both entities are handling a relatively large number of target proteins in a structural genomics approach. Transfer of technology and stra tegies for problem-solving will thus be useful for both research groups.