Curli fibers are required for development of biofilm architecture in Escherichia coli K-12 and enhance bacterial adherence to human uroepithelial cells

Microbiol Immunol. 2005;49(9):875-84. doi: 10.1111/j.1348-0421.2005.tb03678.x.


Sessile bacteria show phenotypical, biochemical, and morphological differences from their planktonic counterparts. Curli, extracellular structures important for biofilm formation, are only produced at temperatures below 30 C in Escherichia coli K-12 strains. In this report, we show that E. coli K-12 can produce curli at 37 C when grown as a biofilm community. The curli-expressing strain formed more biofilms on polyurethane sheets than the curli-deficient strain under growth temperatures of both 25 C and 37 C. Curli are required for the formation of a three-dimensional mature biofilm, with characteristic water channels and pillars of bacteria. Observations by electron microscopy revealed the presence at the surfaces of the curli-deficient mutant in biofilm of flagella and type I pili. A wild-type curli-expressing E. coli strain significantly adhered to several lines of human uroepithelial cells, more so than an isogenic curlideficient strain. The finding that curli are expressed at 37 C in biofilm and enhance bacterial adherence to mammalian host cells suggests an important role for curli in pathogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Adhesion / genetics
  • Bacterial Adhesion / physiology*
  • Biofilms / growth & development*
  • Cell Line
  • Colony Count, Microbial
  • Epithelial Cells / microbiology*
  • Escherichia coli / pathogenicity*
  • Escherichia coli / ultrastructure
  • Fimbriae, Bacterial / physiology*
  • Fimbriae, Bacterial / ultrastructure
  • Flagella / ultrastructure
  • Gene Deletion
  • Humans
  • Temperature
  • Virulence Factors / genetics
  • Virulence Factors / physiology


  • Virulence Factors