Alexandre Lecomte – 17/03/2025

PhD defense :

Study of Enterococcus faecalis intracellular multiplication in hepatocytes

Enterococcus faecalis is a commensal bacterium in the human intestinal microbiota. Although harmless in healthy individuals, E. faecalis is also an opportunistic pathogen. In addition to an association between intestinal overgrowth of E.faecalis and chronic liver disease, E. faecalis is one of the few bacteria that have been shown to play a role in worsening alcohol-induced liver injury. The “Commensalism and Pathogenesis of Enterococci” team has shown that E. faecalis is also able to replicate in hepatocytes, the major parenchymal cells in the liver. The aim of this work was to analyse the mechanisms underlying this multiplication. A targeted approach on the transcriptional regulator CodY allowed us to highlight its role in intracellular multiplication and to propose a model in which CodY is involved in regulating the catabolism of glycerol contained in the lipid droplets of hepatocytes. To identify other bacterial determinants, we screened a transposition library of mutants for their ability to proliferate in hepatocytes. We identified 39 mutants that affect intracellular multiplication but not E. faecalis entry into hepatocytes. One of these mutants is invalidated for the two-component system YclRK, which has been described to be regulated in the presence of metal ions. In parallel, we analysed whether conditions such as intracellular lipid accumulation or alcohol exposure were favourable for intracellular E. faecalis multiplication. In conclusion, this work provided insights into the molecular and cellular mechanisms of interactions between E. faecalis and hepatocytes.

 

Jury members:

  • Cécile MULLER-PUJOL (Université Caen Normandie) – Rapporteur
  • Matteo BONAZZI (CNRS-Institut de Recherche en Infectiologie de Montpellier) – Rapporteur
  • Stéphanie BURY-MONE (Université Paris-Saclay) – Examinatrice
  • Thierry TORDJMANN (INSERM-Université Paris-Saclay) – Examinateur

 

Directed by:

Cristel Archambaud et Anne-Marie Cassard

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