Team Project

This research axis will explore the interconnected roles of virulence factors, secretion systems, and secondary metabolites in the pathogenicity and adaptability of Dickeya and Pectobacterium species. We will focus on the type II secretion system (T2SS), which is essential for secreting pectinases and other virulence proteins. Our studies will include investigating the assembly and function of the T2SS and the unique trait identified in Dickeya dadantii, where several proteins are covalently attached to peptidoglycan; this unexpected feature could influence the secretion processes and contribute to the integrity of the bacterial cell envelope.

Furthermore, we aim to characterize the genetic factors that allow Dickeya to survive outside plant hosts, particularly in different environments where they interact with other microorganisms. Secondary metabolites are central to this adaptability, functioning as competitive agents, signaling molecules, and environmental adaptation tools. By exploring genetic determinants controlling their production and regulation, we seek to understand their role in Dickeya’s environmental resilience and interactions. Our research will specifically focus on the Dickeya solani sol, zms, and ooc secondary metabolite clusters, as well as the newly identified D. dadantii ddm cluster.

This axis will investigate phenotypic variability at the genus, species, and strain levels within the Pectobacteriaceae family. Such variations may arise from gene presence/absence differences or point mutations affecting gene expression. To address this, we employed Tn-seq, a powerful functional genomics tool, to identify genes essential for multiplication, survival and adaptation in specific environments. By generating mutant libraries with random transposon insertions, we can assess gene fitness under different conditions, including plant hosts, water environments, and cold or warm temperatures. By tracking mutant abundance through next-generation sequencing, we can pinpoint key genes and pathways responsible for phenotypic diversity. This approach will be complemented with proteomic analyses to build a comprehensive model of the genetic determinants shaping bacterial environmental resilience. In the coming years, we will primarily exploit the extensive Tn-seq datasets generated during the last period as part of the ANR Tn-Phyto project, which focused on bacterial survival in plants, freshwater, and cold environments.