Besides classical approaches based on culture of microorganisms, we propose a metagenomic approach consisting in the direct cloning of telluric nucleic acids. Libraries so produced will be screened focalising on virulence genes as well as on viruses/phages studied by our two teams : virus and quarantine phytopathogenic bacteria, and on the other hand, virulence genes and phages of Bacillus cereus. All the operations will be carried out under L3 confinement.