Expression of the Escherichia coli IrgA homolog adhesin is regulated by the ferric uptake regulation protein

Rashid, Rebecca A.; Tarr, Phillip I.; Moseley, Steve L.

doi:10.1016/j.micpath.2006.07.006

Cited by 32 publications

(31 citation statements)

References 49 publications

(62 reference statements)

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“…This latter function is consistent with the fact that iha is induced under iron-limiting conditions and is subject to Fur-mediated repression in iron-replete environments in both UPEC and O157:H7 STEC strains (Leveille et al, 2006;Rashid et al, 2006b), as well as in the hyper-virulent LEE-negative STEC strain 98NK2, as shown in this study. However, the mammalian gut is a complex environment and many other compounds may impact on virulence gene expression.…”

Section: Discussionsupporting

confidence: 92%

“…1b). The observation that Iha is better expressed in DMEM than LB medium has been reported previously for O157:H7 STEC, non-O157:H7 STEC and UPEC strains (Johnson et al, 2005;Rashid et al, 2006b;Schmidt et al, 2001). …”

Section: Regulation Of Iha Expression In 98nk2 By Ironsupporting

confidence: 79%

“…As a further preliminary experiment, we examined whether iha expression in the LEE-negative STEC O113:H21 strain 98NK2 is regulated by iron and the Fur protein, as previously reported for UPEC and the LEE-positive STEC O157:H7 strain 86-24 (Leveille et al, 2006;Rashid et al, 2006b). Since Iha functions as a siderophore receptor and the capacity of Iha to transport siderophores is TonBdependent, we also investigated tonB expression under the same conditions.…”

Section: Regulation Of Iha Expression In 98nk2 By Ironmentioning

confidence: 97%

“…The capacity of Iha to transport siderophores is TonB-dependent, whereby the protein complex TonB/ ExbB/ExbD provides the energy required for active transport (Leveille et al, 2006;Postle & Kadner, 2003). Additionally, iha expression is regulated by the ferricuptake regulator protein Fur (Rashid et al, 2006b). In the presence of iron, dimerized Fur binds via a sequence-specific protein-DNA interaction to iha promoter regions and represses iha transcription.…”

Section: Introductionmentioning

confidence: 99%

“…In the presence of iron, dimerized Fur binds via a sequence-specific protein-DNA interaction to iha promoter regions and represses iha transcription. Under ironlimiting conditions, Fur is unable to interact with the DNA and as a consequence, iha transcription is de-repressed (Leveille et al, 2006;Rashid et al, 2006b). Free iron levels are typically low at mucosal surfaces, due to binding by host lactoferrin, and so induction of iron-scavenging mechanisms is an important bacterial in vivo survival strategy.…”

Section: Introductionmentioning

confidence: 99%

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Differential effects of short-chain fatty acids and iron on expression of iha in Shiga-toxigenic Escherichia coli

et al. 2009

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Shiga-toxigenic Escherichia coli (STEC) colonizing the bowel are exposed to a variety of shortchain fatty acids (SCFAs), including acetate, propionate and butyrate, produced by gut microflora. However, the total concentrations and relative amounts of SCFAs in the lumen vary with intestinal niche. Here we report that conditions simulating SCFA concentrations present in the human gut trigger expression of the iha gene, which encodes an adherence-conferring outer-membrane protein of pathogenic E. coli. We show that growth under conditions simulating colonic, but not ileal, SCFA concentrations increases iha expression in three tested STEC strains, with the strongest expression detected in LEE-negative STEC O113:H21 strain 98NK2. Expression of iha is known to be subject to Fur-mediated iron repression in O157:H7 STEC, and the same occurs in 98NK2. However, exogenous iron did not repress iha expression in the presence of colonic SCFAs in either 98NK2 or the O157:H7 strain EDL933. Moreover, exposure to the iron chelator 2,29-dipyridyl caused no further enhancement of iha expression over that induced by colonic SCFAs. These findings indicate that SCFAs regulate iha expression in STEC independently of iron. Increased expression of iha under colonic but not ileal SCFA conditions possibly may contribute to preferential colonization of the human colon by STEC.

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Section: Discussionsupporting

confidence: 92%

Section: Regulation Of Iha Expression In 98nk2 By Ironsupporting

confidence: 79%

Section: Regulation Of Iha Expression In 98nk2 By Ironmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Differential effects of short-chain fatty acids and iron on expression of iha in Shiga-toxigenic Escherichia coli

et al. 2009

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Prevention of bacterial adhesion

Klemm

Vejborg

Hancock

2010

Appl Microbiol Biotechnol

114

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Management of bacterial infections is becoming increasingly difficult due to the emergence and increasing prevalence of bacterial pathogens that are resistant to available antibiotics. Conventional antibiotics generally kill bacteria by interfering with vital cellular functions, an approach that imposes selection pressure for resistant bacteria. New approaches are urgently needed. Targeting bacterial virulence functions directly is an attractive alternative. An obvious target is bacterial adhesion. Bacterial adhesion to surfaces is the first step in colonization, invasion, and biofilm formation. As such, adhesion represents the Achilles heel of crucial pathogenic functions. It follows that interference with adhesion can reduce bacterial virulence. Here, we illustrate this important topic with examples of techniques being developed that can inhibit bacterial adhesion. Some of these will become valuable weapons for preventing pathogen contamination and fighting infectious diseases in the future.

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