Development of intracellular bacterial communities of uropathogenic Escherichia coli depends on type 1 pili

Cell Microbiol. 2007 Sep;9(9):2230-41. doi: 10.1111/j.1462-5822.2007.00952.x. Epub 2007 May 8.


Uropathogenic Escherichia coli, the predominant causative agent of urinary tract infections, use type 1 pili to bind and invade bladder epithelial cells. Upon entry, the bacteria rapidly replicate and enter a complex developmental pathway ultimately forming intracellular bacterial communities (IBCs), a niche with biofilm-like properties protected from innate defences and antibiotics. Paradoxically, bacteria within IBCs produce type 1 pili, an organelle thought only to be an extracellular colonization factor. Thus, we investigated the function of type 1 pili in IBC development. The cystitis isolate, UTI89, was genetically manipulated for conditional fim expression under control of the tet promoter. In this strain, UTI89-tetR/P(tet) fim, piliation is constitutively inhibited by the tetracycline repressor, TetR. Repression is relieved by anhydrotetracycline (AHT) treatment. UTI89-tetR/P(tet) fim and the isogenic control strain, UTI89-tetR, grown in the presence of AHT, colonized the bladder and invaded the superficial umbrella cells at similar levels at early times in a murine model of infection. However, after invasion UTI89-tetR/P(tet) fim became non-piliated and was unable to form typical IBCs comprised of tightly packed, coccoid-shaped bacteria in contrast to the control strain, UTI89-tetR. Thus, this work changes the extracellular colonization functional paradigm of pili by demonstrating their intracellular role in biofilm formation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Bacterial Adhesion / physiology
  • Escherichia coli Infections / metabolism*
  • Escherichia coli* / cytology
  • Escherichia coli* / metabolism
  • Escherichia coli* / pathogenicity
  • Female
  • Fimbriae, Bacterial / metabolism*
  • Guinea Pigs
  • Hemagglutination
  • Mice
  • Mice, Inbred C3H
  • Urinary Tract Infections* / metabolism
  • Urinary Tract Infections* / microbiology
  • Urothelium / cytology
  • Urothelium / metabolism
  • Urothelium / microbiology