title: Escherichia coli O157:H7 adherence to HEp-2 cells is implicated with curli expression and outer membrane integrity.
abstract: Escherichia coli (E. coli) has ability to express thin aggregative fimbriae, known as curli, on the cell surface. Previously, a few example of curli expression in serogroup O157:H7 of enterohemorrhagic E. coli (EHEC) were reported, compared to other E. coli groups. However, significance of curliation in the EHEC pathobiology has not been described well in the literature. A highly curliated O157:H7 strain was used in this study in order to elucidate role of curliation in EHEC adherence to cultured HEp-2 cells. The expression of curli in the EHEC isolate was consistent with strong positive indication of Congo-red (CR) binding and formation of clumps in the bottom of the tube containing Luria-Bertani (LB) broth when cultured overnight at 37 degrees C. A few CR-binding negative (CR-) colonies occurred spontaneously within the population of CR+ isolate. The CR+ EHEC showed massive aggregative adhesion pattern, whereas the spontaneous CR- strain showed typical localized adherence on HEp-2 cells. Electron microscopy confirmed highly curliated bacteria in the CR+ EHEC sample. Interestingly, the curliation disappeared in a msbB1 and msbB2 double mutant derived from the CR+ EHEC. These results suggest that the compromised outer membrane integrity caused by msbB mutations may abrogate curli production in the CR+ EHEC harbouring penta-acylated lipid A structure in their outer membrane.
authors.affiliation: Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Sang-Hyun
authors.initials: SH
authors.lastname: Kim
authors.forename: Yong-Hwan
authors.initials: YH
authors.lastname: Kim
mesh_terms: D001422:Bacterial Adhesion / Q000502:physiology*; D001425:Bacterial Outer Membrane Proteins / Q000502:physiology*; D002449:Cell Aggregation; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000382:microbiology*; D019453:Escherichia coli O157 / Q000472:pathogenicity / Q000502:physiology* / Q000648:ultrastructure; D010861:Fimbriae, Bacterial / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D007830:Larynx / Q000166:cytology / Q000382:microbiology; D008854:Microscopy, Electron
chemical_list: D001425:Bacterial Outer Membrane Proteins