Résumé
The Vfm quorum sensing (QS) system is preponderant for the virulence of different species of the bacterial genus Dickeya. The vfm gene cluster encodes 26 genes involved in the production, sensing or transduction of the Vfm QS signal [1]. It does not share any gene homology with other known QS loci, indicating that both the structure of the Vfm QS signal and its signaling cascade exhibit unique features. The presence of nonribosomal peptide synthetase (NRPS) genes suggests that the Vfm QS signal is a complex short peptide. To date, the latter has escaped detection by analytical chemistry methods. However, a strain-specific polymorphism in the NRPS genes vfmO and vfmP is predicted to be related to the production of different analogues of the QS Vfm signal. Consequently, in several species of Dickeya, the Vfm communication is expected to be impossible between strains possessing different variants of the genes vfmO/P. We constructed three Vfm QS biosensor strains possessing different variants of the genes vfmO/P, and compared these biosensor strains for their responses to samples prepared from 36 Dickeya strains possessing different vfmO/P variants. A pattern of specificity was demonstrated, providing experimental evidence that the polymorphism in the genes vfmO/P determines the production of different analogues of the Vfm QS signal [2]. Unexpectedly, this vfmO/Pdependent pattern of specificity is linked to a polymorphism in the ABC transporter gene vfmG, suggesting an adaptation of the putative permease VfmG to specifically bind different analogues of the Vfm QS signal and to act as co-sensor of the Vfm two-component regulatory system.