Escherichia coli K-12 possesses multiple cryptic but functional chaperone-usher fimbriae with distinct surface specificities

Environ Microbiol. 2010 Jul;12(7):1957-77. doi: 10.1111/j.1462-2920.2010.02202.x. Epub 2010 Mar 23.


Commensal and pathogenic Escherichia coli adherence to host and environmental surfaces is mediated by a variety of adhesins. Although extensively studied as a model bacterium, 34% of the genes in the E. coli K-12 genome have no known function. We hypothesized that some of them may correspond to functional adhesins. We characterized E. coli K-12 ycb, ybg, yfc, yad, yra, sfm and yeh operons, which display sequence and organizational homologies to type 1 fimbriae exported by the chaperone/usher pathway. We showed that, although these operons are poorly expressed under laboratory conditions, six of them are nevertheless functional when expressed, and promote adhesion to abiotic and/or epithelial cell surfaces. While the studied fimbriae display different binding specificities, we obtained evidence of synergy/interference with other adhesins such as Ag43 or type 1 fimbriae. We showed that their expression is under the negative control of H-NS and, except for yad, subjected to cAMP receptor protein-mediated activation and carbon catabolite repression. These results therefore demonstrate that ycb, yfc, yad, yra, sfm and yeh operons encode cryptic but functional fimbriae adhesins whose expression following environmental modifications could contribute to E. coli's ability to adhere to and colonize a wide diversity of surfaces in its various ecological niches.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adhesins, Bacterial / genetics*
  • Adhesins, Bacterial / metabolism
  • Bacterial Adhesion
  • Cell Line
  • Epithelial Cells / microbiology
  • Escherichia coli K12 / chemistry*
  • Escherichia coli Proteins / genetics*
  • Escherichia coli Proteins / metabolism
  • Fimbriae, Bacterial / genetics*
  • Fimbriae, Bacterial / metabolism
  • Gene Deletion
  • Gene Expression Profiling
  • Gene Expression Regulation, Bacterial
  • Gene Order
  • Genes, Bacterial
  • Genes, Reporter
  • Humans
  • Microscopy, Electron, Transmission
  • Mutagenesis, Insertional
  • Operon
  • beta-Galactosidase / genetics
  • beta-Galactosidase / metabolism


  • Adhesins, Bacterial
  • Escherichia coli Proteins
  • beta-Galactosidase