Escherichia coli K-12 possesses multiple cryptic but functional chaperone-usher fimbriae with distinct surface specificities.
Résumé
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
Mots clés
Adhesins
Bacterial/*genetics/metabolism
Bacterial Adhesion
beta-Galactosidase/genetics/metabolism
Cell Line
Epithelial Cells/microbiology
Escherichia coli K12/*chemistry
Escherichia coli Proteins/*genetics/metabolism
Fimbriae
Gene Deletion
Gene Expression Profiling
Gene Expression Regulation
Bacterial
Gene Order
Genes
Reporter
Humans
Microscopy
Electron
Transmission
Mutagenesis
Insertional
Operon