Abstract

Nosocomial infections are a major public health problem, exacerbated by the global spread of bacterial resistance to antibiotics. Faced with this challenge, it is crucial to explore alternatives or complementary strategies to conventional treatments. Among these, the use of copper is attracting renewed interest. This metal has natural antibacterial properties that have been recognized since ancient times. It acts through multiple mechanisms such as membrane alteration, the generation of reactive oxygen species, and the denaturation of proteins and nucleic acids, leading to rapid cell death. These characteristics make it an effective biocidal agent in many contexts, particularly in hospitals.

However, the selective pressure exerted by the increased presence of copper in the environment has led to the emergence of specific resistance systems in certain bacteria. These systems allow strict control of copper homeostasis by limiting its intracellular accumulation through efflux, sequestration, or oxidation mechanisms. In Caulobacter crescentus, an environmental bacterial model, copper resistance is based in particular on the Pco system. This system is composed of the PcoB protein, located in the outer membrane. Although its structure has been partially described in E. coli, its precise function remains unclear. Preliminary observations suggest that it may be involved in the export of copper from the periplasm to the outside of the cell, thus acting as a release pathway.

To explore the role of PcoB in bacterial copper resistance, this study focused on the structural and functional characterization of the protein. After extraction and purification, PcoB was incorporated into artificial liposomes to develop an in vitro transport assay to assess its ability to release copper across a lipid bilayer. At the same time, a truncated mutant lacking the disordered N-terminal region was produced and subjected to the same analyses. The comparison between the complete and truncated forms aims to determine the involvement of this flexible region in the transport mechanism and stability of the protein. These approaches have laid the initial experimental foundations for studying the transport mechanism of PcoB and constitute a first step towards a detailed understanding of how the Pco system works. They also open up prospects for the development of new antibacterial strategies targeting copper management systems in bacteria.

Jury

  • Prof. Johan WOUTERS (UNamur), Chair
  • Dr. Catherine MICHAUX (UNamur), Secretary
  • Prof. Jean-Yves MATROULE (UNamur)
  • Dr. Guillaume ROUSSEL (UCLouvain)
  • Prof. Francesca CECCHET (UNamur)
  • Prof. Hennie VALKENIER (ULB)