The sequence of the universal bacterial DNA repair protein Mfd dictates the pathogenicity of Bacillus cereus strains

International audience ; The bacterial protein Mfd (mutation frequency decline) is highly conserved among bacteriaand has been shown to be involved in bacterial DNA repair. We have recently shown thatthis protein confers bacterial resistance to the host nitrogen response produced during aninfection by the immune system. Indeed, Mfd helps preserving DNA integrity and is involvedin the repair following NO-induced DNA damage. Using a large collection of Bacillus cereusstrains with various pathogenicity, we could further establish a link between Mfd sequences,protein 3D structures and virulence. Protein sequence comparison and 3D modelling wereused to determine specific domains involved in the virulence of B. cereus. Using an in vivoinsect model of infection, we show that the mfd gene of a pathogenic strain couldcomplement the avirulent phenotype of a non-pathogenic strain. These data stronglysuggest that the 3D structure of Mfd plays an essential role in its function and might be anew and interesting way to discriminate pathogenic from harmless B. cereus strains.As Mfd is widely conserved within bacteria, those findings could improve our understandingon the pathogenicity of potentially a large spectrum of bacteria.