Mfd-Mutation frequency decline-protein is ubiquitous and involved in bacterial DNA repair. Mfd confers bacterial protection against the nitric oxid immune response mounted by the host during infection 1-2. Mfd preserves DNA integrity, helps to repair DNA damage. Reversely, its neutralization empowers the host immune system. Issue: are there patterns in sequence, and 3D markers in structure of Mfd that could explain the clinic vs non-pathogenic phenotype of Bacillus cereus? Mfd alignment in B. cereus separates pathogenic vs non pathogenic strains. Using an in vivo insect model of infection, we are currently testing if mfd gene of a pathogenic strain complements a non-pathogenic strain and viceversa, if Mfd gene of a non-pathogenic strain could complement the virulent phenotype of a pathogenic strain. Also, residues identified as substituted will be shortly site-directed mutated.