Cell-Size Homeostasis and the Incremental Rule in a Bacterial Pathogen

Biophys J. 2015 Aug 4;109(3):521-8. doi: 10.1016/j.bpj.2015.07.002.


How populations of growing cells achieve cell-size homeostasis remains a major question in cell biology. Recent studies in rod-shaped bacteria support the "incremental rule" where each cell adds a constant length before dividing. Although this rule explains narrow cell-size distributions, its mechanism is still unknown. We show that the opportunistic pathogen Pseudomonas aeruginosa obeys the incremental rule to achieve cell-length homeostasis during exponential growth but shortens its cells when entering the stationary phase. We identify a mutant, called frik, which has increased antibiotic sensitivity, cells that are on average longer, and a fraction of filamentous cells longer than 10 μm. When growth slows due to entry in stationary phase, the distribution of frik cell sizes decreases and approaches wild-type length distribution. The rare filamentous cells have abnormally large nucleoids, suggesting that a deficiency in DNA segregation prevents cell division without slowing the exponential elongation rate.

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Cell Cycle*
  • Homeostasis*
  • Mutation
  • Pseudomonas aeruginosa / cytology*
  • Pseudomonas aeruginosa / drug effects
  • Pseudomonas aeruginosa / genetics
  • Pseudomonas aeruginosa / physiology


  • Anti-Bacterial Agents