Type 2 Secretion Promotes Enterohemorrhagic Escherichia coli Adherence and Intestinal Colonization

Abstract

Enterohemorrhagic Escherichia coli (EHEC) is a noninvasive food-borne pathogen that colonizes the distal ileum and colon. Proteins encoded in the EHEC locus of enterocyte effacement (LEE) pathogenicity island are known to contribute to this pathogen's adherence to epithelial cells and intestinal colonization. The role of non-LEE-encoded proteins in these processes is not as clear. We found that the Z2053 gene (designated adfO here), a gene located in a cryptic EHEC prophage, exhibits similarity to adherence and/or colonization factor genes found in several other enteric pathogens. An EHEC adfO mutant exhibited marked reductions in adherence to HeLa cells and in the secretion of several proteins into the supernatant. YodA, one of these secreted proteins, was found to be a substrate of the EHEC pO157-encoded type 2 secretion system (T2SS). Both the T2SS and YodA proved to be essential for EHEC adherence to cultured HeLa cell monolayers. Using an infant rabbit model of infection, we found that the adfO mutation did not affect colonization but that the colonization of an etpC (T2SS) mutant was reduced ϳ5-fold. A strain deficient in YodA had a more severe colonization defect; however, this strain also exhibited a growth defect in vitro. Overall, our findings indicate that the pO157-encoded T2SS contributes to EHEC adherence and intestinal colonization and thus show that EHEC pathogenicity depends on type 2 secretion as well as type 3 secretion.

Differences in adherence and virulence gene expression between two outbreak strains of enterohaemorrhagic Escherichia coli O157 : H7

“…Mutation of etpC, the first gene in the etp operon, has been shown to result in a significant reduction of O157 : H7 colonization in an infant rabbit model of disease (Ho et al, 2008). In this study, two effectors of type II secretion previously suggested to contribute to adherence, StcE (Grys et al, 2005) and AdfO (Ho et al, 2008), were upregulated in TW14359.…”

“…Mutation of etpC, the first gene in the etp operon, has been shown to result in a significant reduction of O157 : H7 colonization in an infant rabbit model of disease (Ho et al, 2008). In this study, two effectors of type II secretion previously suggested to contribute to adherence, StcE (Grys et al, 2005) and AdfO (Ho et al, 2008), were upregulated in TW14359. The StcE metalloprotease, the expression of which is positively influenced by Ler (Lathem et al, 2002), is hypothesized to promote adherence by cleaving proteins in the glycocalyx and mucin layers atop the intestinal epithelium, facilitating close contact with the intestinal mucosa (Grys et al, 2005).…”

“…The StcE metalloprotease, the expression of which is positively influenced by Ler (Lathem et al, 2002), is hypothesized to promote adherence by cleaving proteins in the glycocalyx and mucin layers atop the intestinal epithelium, facilitating close contact with the intestinal mucosa (Grys et al, 2005). The contribution of AdfO to adherence is not clear, as an adfO mutation has been shown to markedly decrease epithelial cell adherence in vitro, but does not attenuate colonization following oral challenge of infant rabbits (Ho et al, 2008).…”

“…The transcription of one such gene, stcE (tagA), which encodes a metalloprotease that contributes to intimate adherence (Grys et al, 2005), was elevated in TW14359. Expression of adfO (ECs1772), which encodes another type II secretion effector that promotes adherence of O157 : H7 to epithelial cells (Ho et al, 2008), was also elevated in TW14359. Overall, these results indicate that the transcription of major and accessory colonization factors, preceding intimate adherence of O157 : H7 to MAC-T epithelial cells, is higher in TW14359 than Sakai.…”

Change Is Good: Variations in Common Biological Mechanisms in the Epsilonproteobacterial GeneraCampylobacterandHelicobacter

“…In addition to being a conduit for transport of secreted effector proteins, the EspA filament of the LEE-encoded T3SS has also been implicated in adherence of EPEC strains (103). Additionally, the EHEC virulence plasmid pO157 encodes the Etp T2SS along with YodA and StcE, two Etp-secreted factors that influence adhesion processes (228,259). yodA mutants of EHEC demonstrate reduced adherence to HeLa cells and are less competitive for colonization of the rabbit intestine (259).…”