Identification of a new iron regulated locus of Salmonella typhi

Bäumler, Andreas J.; Tsolis, Renée M.; Velden, Adrianus W. M. van der; Stojiljković, Igor; Anic, Suzana; Heffron, Fred

doi:10.1016/s0378-1119(96)00560-4

Cited by 153 publications

(128 citation statements)

References 31 publications

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“…The sensitivity of PCR was determined to be 96%. Several studies have reported high sensitivity of PCR of blood for S.Typhi [9,14]. PCR detected iroB gene in 31 out of the 60 blood samples (51.6%).The sensitivity of PCR was determined to be 96.6%.…”

Section: Discussionmentioning

confidence: 94%

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Detection of Salmonella in Blood by PCR using iroB gene

Ganesan

Harish

Menezes

et al. 2014

JCDR

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Section: Discussionmentioning

confidence: 94%

“…Two genetic regions on the S. enterica chromosome, Salmonella pathogenicity island 2 and the iroBC operon, indeed show this phylogenetic distribution [9].…”

Section: Introductionmentioning

confidence: 88%

Detection of Salmonella in Blood by PCR using iroB gene

Ganesan

Harish

Menezes

et al. 2014

JCDR

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“…Growth response to siderophores was tested on nutrient broth plates (8 g of nutrient broth, 5 g of NaCl, and 15 g of Difco agar per liter) containing 0.2 mM 2,2Ј-dipyridyl; the plates were seeded with the appropriate strain in 2.5 ml of soft agar in water. Filter-paper discs loaded with 15 l of siderophore solution were applied, and growth zones were measured after 18 h. Strain AIR50 has been constructed by A. Bäumler and his group (Texas A&M University, College Station) by inserting a kanamycin resistance cassette into the unique BglII site of iroD and introducing this mutation by gene replacement in a similar way as described for AIR49 (4,5). S. enterica serotype Stanleyville strains H5546 and H5547 were constructed by P22 transduction of the aroA ϩ gene from S. enterica serotype Typhimurium strain LT2.…”

Section: Methodsmentioning

confidence: 99%

“…Recently, the iroA locus, consisting of the two convergent operons iroN and iroBCDE, has been defined in S. enterica serotype Typhi and also in most other S. enterica serotypes (4,5). The outer membrane siderophore receptor, IroN, is involved in the transport of several catecholate siderophores in S. enterica (5,6).…”

mentioning

confidence: 99%

Salmochelins, siderophores of Salmonella enterica and uropathogenic Escherichia coli strains, are recognized by the outer membrane receptor IroN

Hantke

Nicholson

Rabsch

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

322

368

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Members of a family of catecholate siderophores, called salmochelins, were isolated by reversed-phase HPLC from Salmonella enterica serotype Typhimurium and structurally characterized by Fourier transform ion cyclotron resonance-MS͞MS and GC-MS. The tentative structure of salmochelin 1 contained two 2,3-dihydroxybenzoylserine moieties bridged by a glucose residue, bound to the serine hydroxyl group of one moiety and the carboxylate of the second moiety. Salmochelin 2 contained in addition a second glucose residue linked to a third 2,3-dihydroxybenzoylserine moiety. Salmochelins were not produced by an iroBC mutant, which indicated that the IroB protein might be responsible for the glucosyl transfer predicted by sequence similarities to known glycosyltransferases. Uptake experiments with radiolabeled 55 Fe-salmochelin and growth promotion tests with salmochelins showed that the IroN outer membrane receptor, encoded in the iroA locus of S. enterica and uropathogenic Escherichia coli strains, was the main receptor for ferric salmochelin transport.I n iron-poor environments, many bacteria secrete ironcomplexing agents called siderophores to satisfy their iron needs. For some pathogenic bacteria, siderophores are important virulence factors because iron is bound to transferrin and lactoferrin in body fluids. These proteins reduce the free Fe 3ϩ concentration to about one molecule per liter. Enterobacteria, including Escherichia coli and Salmonella enterica, often produce the catecholate siderophore enterochelin (also called enterobactin) (1, 2). It has been postulated that enterochelin is an inferior siderophore in serum because it adsorbs to hydrophobic sites in serum proteins, such as albumin (3). This fact has always been puzzling because iron supply for many pathogens plays a decisive role in the infection process, and enterochelin, a major siderophore synthesized by S. enterica, does not seem to enhance pathogenicity.Recently, the iroA locus, consisting of the two convergent operons iroN and iroBCDE, has been defined in S. enterica serotype Typhi and also in most other S. enterica serotypes (4, 5). The outer membrane siderophore receptor, IroN, is involved in the transport of several catecholate siderophores in S. enterica (5, 6). In the present investigation, we show that the presence of the iro gene cluster in S. enterica leads to glycosylation of the enterochelin building block 2,3-dihydroxybenzoylserine (DHBS), which makes the hydrophobic enterochelin molecules more hydrophilic, thereby possibly contributing to the observed pathogenicity of Salmonella strains. This siderophore was named salmochelin because it appears to be a characteristic siderophore of Salmonella strains. Interestingly, certain E. coli strains, e.g., the uropathogenic E. coli 563, also possess a very similar iro gene cluster on pathogenicity island III (7). The production and the tentative structural elucidation of salmochelins and their specific uptake via the outer membrane receptor IroN are described. In addition, it is shown that salmo...

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“…Production of salmochelins is associated with the iroA gene cluster (Fig. 1B), which is also found in pathogenic strains of E. coli, Salmonella spp., and K. pneumoniae (9)(10)(11)(12). The iroA gene cluster encodes five proteins involved in modification and transport of Ent: IroB Cglucosylates Ent (13), IroE hydrolytically linearizes Ent (14,15), IroD degrades ferric complexes of the siderophore to release iron in the bacterial cytoplasm (14,15), and IroN and IroC transport Ent and its derivatives (16).…”

mentioning

confidence: 99%

The pathogen-associated iroA gene cluster mediates bacterial evasion of lipocalin 2

Fischbach

Lin

Zhou

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

274

243

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Numerous bacteria cope with the scarcity of iron in their microenvironment by synthesizing small iron-scavenging molecules known as siderophores. Mammals have evolved countermeasures to block siderophore-mediated iron acquisition as part of their innate immune response. Secreted lipocalin 2 (Lcn2) sequesters the Escherichia coli siderophore enterobactin (Ent), preventing E. coli from acquiring iron and protecting mammals from infection by E. coli. Here, we show that the iroA gene cluster, found in many pathogenic strains of Gram-negative enteric bacteria, including E. coli, Salmonella spp., and Klebsiella pneumoniae, allows bacteria to evade sequestration of Ent by Lcn2. We demonstrate that Cglucosylated derivatives of Ent produced by iroA-encoded enzymes do not bind purified Lcn2, and an iroA-harboring strain of E. coli is insensitive to the growth inhibitory effects of Lcn2 in vitro. Furthermore, we show that mice rapidly succumb to infection by an iroA-harboring strain of E. coli but not its wild-type counterpart, and that this increased virulence depends on evasion of host Lcn2. Our findings indicate that the iroA gene cluster allows bacteria to evade this component of the innate immune system, rejuvenating their Ent-mediated iron-acquisition pathway and playing an important role in their virulence.bacterial pathogens ͉ host defense ͉ innate immunity ͉ iron ͉ siderophores

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Identification of a new iron regulated locus of Salmonella typhi

Cited by 153 publications

References 31 publications

Detection of Salmonella in Blood by PCR using iroB gene

Detection of Salmonella in Blood by PCR using iroB gene

Salmochelins, siderophores of Salmonella enterica and uropathogenic Escherichia coli strains, are recognized by the outer membrane receptor IroN

The pathogen-associated iroA gene cluster mediates bacterial evasion of lipocalin 2

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