K+-dependent cell cycle regulation in Caulobacter crescentus

  • Madeline Collignon

Student thesis: Master typesMaster in molecular microbiology, research focus


Potassium (K+) is the most abundant cation in all living cells. Besides its neutralizing and osmoprotective functions, this ion is crucial to the activity of the ribosomes and many intracellular enzymes. K+ is also an important regulator of bacterial physiology as it is involved in diverse processes including biofilm formation, chemotaxis, cell to cell communication or virulence. Yet the role of K+ in the bacterial cell cycle remains uncharacterized. By using flow cytometry, we have demonstrated in this work that K+ is essential for cell cycle progression in Caulobacter crescentus. This α-proteobacterium possesses a putative K+ channel and two K+-uptake systems, Kup and Kdp. Presumably involved in K+ uptake in low K+ conditions, we have investigated the role of the Kdp transporter and the one of the KdpD/E two-component signal transduction system that regulates kdp expression. Deletion of the Kdp system impaired growth exclusively in low K+, suggesting that as in E. coli, Kdp is mainly active in K+ limiting conditions. In contrast, the KdpD/E two-component system seems to function in a different fashion. Both deletion and catalytic inactivation of the sensor kinase KdpD resulted in a growth surpassing the wild-type strain in low K+ conditions. We found that the kdp operon was expressed even without KdpD activation, thus arguing for an alternative phosphodonor for its cognate response regulator KdpE. Our data also suggest that Kdp is likely involved in the K+-dependent cell cycle progression. Overall, our work highlights the unsuspected and central role of K+ in bacterial cell cycle regulation.
Date of Award21 Jan 2021
Original languageEnglish
Awarding Institution
  • University of Namur
SupervisorRegis Hallez (Supervisor)


  • Potassium
  • cell cycle

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