Abstract
Phytopathogenic bacteria of the genus Dickeya cause significant damage to various crops, threatening entire sectors of global food supply. Dickeya species utilize a unique quorum sensing (QS) system called Vfm, which allows them to synchronize the expression of virulence-associated genes within a bacterial population once the concentration of signal molecules reaches a threshold. Detection of the signal molecule by bacteria triggers a cascade of reactions that activate the transcriptional regulator VfmE, a key player in inducing virulence genes, including those coding for plant cell wall-degrading enzymes, leading to soft rot symptoms.The originality of the Vfm QS system lies in the non-ribosomal peptide nature of the signal molecule and the existence of intraspecific specificity groups caused by polymorphisms in the genes responsible for signal synthesis and perception. This polymorphism leads to the production of three signal analogs and the expression of three corresponding specific receptors.This thesis aims to contribute to the understanding of the Vfm QS system and its potential impact on the pathogenicity of Dickeya. The research is guided by three objectives: (i) developing a strategy to extract and purify the Vfm signal molecule for chemical characterization, (ii) analyzing the influence of vfm gene polymorphisms on the expression of the vfmE gene, and (iii) comparing the activity of the Vfm QS system in congenic strains expressing alleles corresponding to different specificity groups.