• Régis Hallez's Research Group
  • Régis Hallez's Research Group
  • Régis Hallez's Research Group
  • Régis Hallez's Research Group
  • Régis Hallez's Research Group
  • Régis Hallez's Research Group
  • Régis Hallez's Research Group
  • Régis Hallez's Research Group
  • Régis Hallez's Research Group
  • Régis Hallez's Research Group

Research

Response to stressful conditions

To survive to fluctuating environments, bacteria have evolved complex regulatory pathways that sense and respond adequately to changing conditions. One of these systems used by literally all bacteria is based on the alarmone (p)ppGpp. This second messenger accumulates upon starvation to essential elements (carbon, nitrogen, phosphorus, …), and the burst of (p)ppGpp modulates several cellular processes (transcription, metabolism, growth, cell cycle, virulence, …).

By combining genetic and biochemical approaches in our bacterial models, we (i) characterize mechanisms that trigger (p)ppGpp accumulation in  response to nutritional stresses and (ii) look for direct (p)ppGpp targets.

We also characterize two-component signal transductions systems (TCS) involved in stress response. 

 
 
Metabolic control of the cell cycle

The dimorphic life cycle of C. crescentus is the result of an obligate asymmetric cell division that gives rise to a larger stalked cell and a smaller swarmer cell. The swarmer progeny is specialized for dispersal whereas the stalked cell helps in colonizing favorable substrates. Whereas the stalked cell is able to immediately re-initiate a new round of replication and cell division, the swarmer cell remains in a motile, replication inert phase (G1) before differentiating into a replication-competent stalked cell. Exit from G1 is controlled by environmental factors like nutrient availability, but also by regulatory systems, and Caulobacter cells use metabolic checkpoints to modulate cell cycle and development depending on nutrient availability. We investigate the molecular basis of these metabolic checkpoints, in particular those used to coordinate metabolism with cell division. We also study the molecular mechanisms determining the time spent in G1 phase as well as the factors triggering the G1-to-S transition.

 
 
Cell cycle, metabolism and virulence

Brucella abortus is an intracellular pathogen that shares several common features with C. crescentus such as an asymmetric cell division and regulatory pathways controlling cell cycle and differentiation. Moreover the cell cycle is tightly controlled during infection of host cells and metabolism plays a crucial role in Brucella virulence. Our studies on B. abortus aim at understanding how metabolism and cell cycle are coordinated during intracellular invasion.

Acinetobacter baumannii is an opportunsitic pathogen classified by the WHO as a critical MDR-bacterium armed with many mechanisms allowing to resist to most of antibiotics. We study the the impact of the alarmone (p)ppGpp on the cell cycle, metabolism, antibiotic resistance/tolerance and virulence of A. baumannii.