A Double, Long Polar Fimbria Mutant of Escherichia coli O157:H7 Expresses Curli and Exhibits Reduced In Vivo Colonization

Abstract

Escherichia coli O157:H7 causes food and waterborne enteric infections that can result in hemorrhagic colitis and lifethreatening hemolytic uremic syndrome. Intimate adherence of the bacteria to intestinal epithelial cells is mediated by intimin, but E. coli O157:H7 also possess several other putative adhesins, including curli and two operons that encode long polar fimbriae (Lpf). To assess the importance of Lpf for intestinal colonization, we performed competition experiments between E. coli O157:H7 and an isogenic ⌬lpfA1 ⌬lpfA2 double mutant in the infant rabbit model. The mutant was outcompeted in the ileum, cecum, and midcolon, suggesting that Lpf contributes to intestinal colonization. In contrast, the ⌬lpfA1 ⌬lpfA2 mutant showed increased adherence to colonic epithelial cells in vitro. Transmission electron microscopy revealed curli-like structures on the surface of the ⌬lpfA1 ⌬lpfA2 mutant, and the presence of curli was confirmed by Congo red binding, immunogold-labeling electron microscopy, immunoblotting, and quantitative real-time reverse transcription-PCR (qRT-PCR) measuring csgA expression. However, deletion of csgA, which encodes the major curli subunit, does not appear to affect intestinal colonization. In addition to suggesting that Lpf can contribute to EHEC intestinal colonization, our observations indicate that the regulatory pathways governing the expression of Lpf and curli are interdependent.

Curli Temper Adherence of Escherichia coli O157:H7 to Squamous Epithelial Cells from the Bovine Recto-Anal Junction in a Strain-Dependent Manner

“…These adherence factors readily compensate for curli and increase O157 adherence to RSE cells when curli are absent. Additional factors have been associated with biofilm formation and/or adherence in bacteria, including cellulose, long polar fimbriae, serine proteases, enterohemolysins, colanic acid, and extracellular polysaccharides (39)(40)(41)(42)(43)(44)(45), and these may also influence adherence to RSE cells. Hence, studying curli and other compensating adherence factors for relevant cell types is critical in designing efficacious, host-specific, anti-O157 adherence, preharvest strategies.…”

Surface adhesins and exopolymers of selected foodborne pathogens

“…the extracellular nucleation-precipitation pathway (Chagnot et al, 2013;Desvaux et al, 2009). While generally considered as very important for adhesion by its subunit protein CsgA, curli were shown not to contribute to intestinal colonization in E. coli O157 : H7 (Lloyd et al, 2012). The E. coli common pilus (ECP, yagZ), also called meningitisassociated and temperature-regulated (Mat) fimbriae (Lehti et al, 2013), is an important colonization factor involved not only in adhesion to epithelial cells (Rendó n et al, 2007) but also in the early stage of biofilm formation (Garnett et al, 2012).…”

Actin Pedestal Formation by Enterohemorrhagic Escherichia coli Enhances Bacterial Host Cell Attachment and Concomitant Type III Translocation

“…First, initial attachment may be mediated by several candidate factors, some unrelated to type III secretion (15,16). For example, a type III secretion system filamentous appendage comprised of EspA may promote initial attachment to the mammalian cell surface (17,18), and type IV pili promote attachment to mammalian cells (19)(20)(21)(22).…”