J Vet Sci.  2004 Jun;5(2):119-124.

Escherichia coli O157:H7 adherence to HEp-2 cells is implicated with curli expression and outer membrane integrity

• Kim SH
• Kim YH

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 degress 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.

Keyword

E. coli O157:H7; Curli; Adhesion; HEp-2 cells

MeSH Terms

Bacterial Adhesion/*physiology
Bacterial Outer Membrane Proteins/*physiology
Cell Aggregation
Cells, Cultured
Epithelial Cells/*microbiology
Escherichia coli O157/pathogenicity/*physiology/ultrastructure
Fimbriae, Bacterial/*metabolism/ultrastructure
Humans
Larynx/cytology/microbiology
Microscopy, Electron