scholarly journals Anaerobic Regulation of Shigella flexneri Virulence: ArcA Regulates fur and Iron Acquisition Genes

2007 ◽  
Vol 189 (19) ◽  
pp. 6957-6967 ◽  
Author(s):  
Megan L. Boulette ◽  
Shelley M. Payne
Keyword(s):  
Transcription Factors ◽  
Transport System ◽  
Iron Transport ◽  
Iron Acquisition ◽  
Shigella Flexneri ◽  
Plaque Assay ◽  
Plaque Formation ◽  
Transport Systems ◽  
Dependent Manner ◽  
Anaerobic Conditions

ABSTRACT Invasion and plaque formation in epithelial monolayers are routinely used to assess the virulence of Shigella flexneri, a causative agent of dysentery. A modified plaque assay was developed to identify factors contributing to the virulence of S. flexneri under the anaerobic conditions present in the colon. This assay demonstrated the importance of the ferrous iron transport system Feo, as well as the global transcription factors Fur, ArcA, and Fnr, for Shigella plaque formation in anoxic environments. Transcriptional analyses of S. flexneri iron transport genes indicated that anaerobic conditions activated feoABC while repressing genes encoding two other iron transport systems, the ABC transporter Sit and the Iuc/Iut aerobactin siderophore synthesis and transport system. The anaerobic transcription factors ArcA and Fnr activated expression of feoABC, while ArcA repressed iucABCD iutA. Transcription of fur, encoding the iron-responsive transcriptional repressor of bacterial iron acquisition, was also repressed anaerobically in an ArcA-dependent manner.

scholarly journals Characterization of Ferric and Ferrous Iron Transport Systems in Vibrio cholerae

2006 ◽  
Vol 188 (18) ◽  
pp. 6515-6523 ◽  
Author(s):  
Elizabeth E. Wyckoff ◽  
Alexandra R. Mey ◽  
Andreas Leimbach ◽  
Carolyn F. Fisher ◽  
Shelley M. Payne
Keyword(s):  
Vibrio Cholerae ◽  
Transport System ◽  
Iron Transport ◽  
Iron Acquisition ◽  
Shigella Flexneri ◽  
Transport Systems ◽  
Infant Mouse ◽  
Mouse Intestine ◽  
Dependent Transport

ABSTRACT Vibrio cholerae has multiple iron acquisition systems, including TonB-dependent transport of heme and of the catechol siderophore vibriobactin. Strains defective in both of these systems grow well in laboratory media and in the infant mouse intestine, indicating the presence of additional iron acquisition systems. Previously uncharacterized potential iron transport systems, including a homologue of the ferrous transporter Feo and a periplasmic binding protein-dependent ATP binding cassette (ABC) transport system, termed Fbp, were identified in the V. cholerae genome sequence. Clones encoding either the Feo or the Fbp system exhibited characteristics of iron transporters: both repressed the expression of lacZ cloned under the control of a Fur-regulated promoter in Escherichia coli and also conferred growth on a Shigella flexneri mutant that has a severe defect in iron transport. Two other ABC transporters were also evaluated but were negative by these assays. Transport of radioactive iron by the Feo system into the S. flexneri iron transport mutant was stimulated by the reducing agent ascorbate, consistent with Feo functioning as a ferrous transporter. Conversely, ascorbate inhibited transport by the Fbp system, suggesting that it transports ferric iron. The growth of V. cholerae strains carrying mutations in one or more of the potential iron transport genes indicated that both Feo and Fbp contribute to iron acquisition. However, a mutant defective in the vibriobactin, Fbp, and Feo systems was not attenuated in a suckling mouse model, suggesting that at least one other iron transport system can be used in vivo.

scholarly journals Characterization of the Yersinia pestisYfu ABC Inorganic Iron Transport System

2001 ◽  
Vol 69 (5) ◽  
pp. 2829-2837 ◽  
Author(s):  
Shimei Gong ◽  
Scott W. Bearden ◽  
Valerie A. Geoffroy ◽  
Jacqueline D. Fetherston ◽  
Robert D. Perry
Keyword(s):  
Transport System ◽  
Iron Transport ◽  
Iron Acquisition ◽  
Lethal Dose ◽  
In Vitro Transcription ◽  
Defined Medium ◽  
Transport Systems ◽  
Regulation Of Transcription ◽  
Iron Deficient

ABSTRACT In Yersinia pestis, the causative agent of plague, two inorganic iron transport systems have been partially characterized. The yersiniabactin (Ybt) system is a siderophore-dependent transport system required for full virulence. Yfe is an ABC transport system that accumulates both iron and manganese. We have identified and cloned aY. pestis yfuABC operon. The YfuABC system is a member of the cluster of bacterial ABC iron transporters that include Sfu ofSerratia, Hit of Haemophilus, and Yfu ofYersinia enterocolitica. The Y. pestis KIM6+ system is most homologous to that in Y. enterocolitica, showing identities of 84% for YfuA (periplasmic binding protein), 87% for YfuB (inner membrane permease), and 75% for YfuC (ATP hydrolase). We constructed a yfuABC promoter-lacZ fusion to examine regulation of transcription. This promoter contains a potential Fur binding sequence and is iron and Fur regulated. Significant expression from the yfuABC promoter occurred during iron-deficient growth conditions. In vitro transcription and translation of a recombinant plasmid encoding yfuABCindicates that YfuABC proteins are expressed. Escherichia coli 1017 (an enterobactin-deficient mutant) carrying this plasmid was able to grow in an iron-restrictive complex medium. We constructed a deletion encompassing the yfuABC promoter and most of yfuA. This mutation was introduced into strains with mutations in Ybt, Yfe, or both systems to examine the role of Yfu in iron acquisition in Y. pestis. Growth of theyfu mutants in a deferrated, defined medium (PMH2) at 26 and 37°C failed to identify a growth or iron transport defect due to the yfu mutation. Fifty percent lethal dose studies in mice did not demonstrate a role for the Yfu system in mammalian virulence.

scholarly journals DNA Sequence of a ColV Plasmid and Prevalence of Selected Plasmid-Encoded Virulence Genes among Avian Escherichia coli Strains

2006 ◽  
Vol 188 (2) ◽  
pp. 745-758 ◽  
Author(s):  
Timothy J. Johnson ◽  
Kylie E. Siek ◽  
Sara J. Johnson ◽  
Lisa K. Nolan
Keyword(s):  
Escherichia Coli ◽  
Dna Sequence ◽  
Transport System ◽  
Iron Transport ◽  
Virulence Genes ◽  
Iron Acquisition ◽  
Transport Systems ◽  
E Coli ◽  
Virulence Traits ◽  
Associated Sequences

ABSTRACT ColV plasmids have long been associated with the virulence of Escherichia coli, despite the fact that their namesake trait, ColV production, does not appear to contribute to virulence. Such plasmids or their associated sequences appear to be quite common among avian pathogenic E. coli (APEC) and are strongly linked to the virulence of these organisms. In the present study, a 180-kb ColV plasmid was sequenced and analyzed. This plasmid, pAPEC-O2-ColV, possesses a 93-kb region containing several putative virulence traits, including iss, tsh, and four putative iron acquisition and transport systems. The iron acquisition and transport systems include those encoding aerobactin and salmochelin, the sit ABC iron transport system, and a putative iron transport system novel to APEC, eit. In order to determine the prevalence of the virulence-associated genes within this region among avian E. coli strains, 595 APEC and 199 avian commensal E. coli isolates were examined for genes of this region using PCR. Results indicate that genes contained within a portion of this putative virulence region are highly conserved among APEC and that the genes of this region occur significantly more often in APEC than in avian commensal E. coli. The region of pAPEC-O2-ColV containing genes that are highly prevalent among APEC appears to be a distinguishing trait of APEC strains.

scholarly journals Genetics and Virulence Association of the Shigella flexneri Sit Iron Transport System

2009 ◽  
Vol 77 (5) ◽  
pp. 1992-1999 ◽  
Author(s):  
Carolyn R. Fisher ◽  
Nicola M. L. L. Davies ◽  
Elizabeth E. Wyckoff ◽  
Zhengyu Feng ◽  
Edwin V. Oaks ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Transport System ◽  
Iron Transport ◽  
Shigella Flexneri ◽  
Lung Model ◽  
Mouse Lung ◽  
Wild Type ◽  
Insertion Elements ◽  
Wild Type Parent

ABSTRACT The sit-encoded iron transport system is present within pathogenicity islands in all Shigella spp. and some pathogenic Escherichia coli strains. The islands contain numerous insertion elements and sequences with homology to bacteriophage genes. The Shigella flexneri sit genes can be lost as a result of deletion within the island. The formation of deletions was dependent upon RecA and occurred at relatively high frequency. This suggests that the sit region is inherently unstable, yet sit genes are maintained in all of the clinical isolates tested. Characterization of the sitABCD genes in S. flexneri indicates that they encode a ferrous iron transport system, although the genes are induced aerobically. The sit genes provide a competitive advantage to S. flexneri growing within epithelial cells, and a sitA mutant is outcompeted by the wild type in cultured epithelial cells. The Sit system is also required for virulence in a mouse lung model. The sitA mutant was able to infect the mice and induce a protective immune response but was avirulent compared to its wild-type parent strain.

scholarly journals Disentangling the Evolutionary History of Feo, the Major Ferrous Iron Transport System in Bacteria

mBio ◽  
2022 ◽  
Author(s):  
Camilo Gómez-Garzón ◽  
Jeffrey E. Barrick ◽  
Shelley M. Payne
Keyword(s):  
Transport System ◽  
Ferrous Iron ◽  
Evolutionary History ◽  
Iron Transport ◽  
Iron Acquisition ◽  
Low Oxygen ◽  
Iron Transporter ◽  
Host Pathogen ◽  
History Of ◽  
Ferrous Iron Transport

Feo, a ferrous iron transport system composed of three proteins (FeoA, -B, and -C), is the most prevalent bacterial iron transporter. It plays an important role in iron acquisition in low-oxygen environments and some host-pathogen interactions.

Campylobacter jejuni gene expression in response to iron limitation and the role of Fur

Microbiology ◽  
2005 ◽  
Vol 151 (1) ◽  
pp. 243-257 ◽  
Author(s):  
Kathryn Holmes ◽  
Francis Mulholland ◽  
Bruce M. Pearson ◽  
Carmen Pin ◽  
Johanna McNicholl-Kennedy ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Iron Transport ◽  
Iron Homeostasis ◽  
Iron Acquisition ◽  
Fumarate Hydratase ◽  
Iron Limitation ◽  
Transport Systems ◽  
Wild Type ◽  
Mobility Shift

Campylobacter jejuni is a zoonotic pathogen and the most common cause of bacterial foodborne diarrhoeal illness worldwide. To establish intestinal colonization prior to either a commensal or pathogenic interaction with the host, C. jejuni will encounter iron-limited niches where there is likely to be intense competition from the host and normal microbiota for iron. To gain a better understanding of iron homeostasis and the role of ferric uptake regulator (Fur) in iron acquisition in C. jejuni, a proteomic and transcriptome analysis of wild-type and fur mutant strains in iron-rich and iron-limited growth conditions was carried out. All of the proposed iron-transport systems for haemin, ferric iron and enterochelin, as well as the putative iron-transport genes p19, Cj1658, Cj0177, Cj0178 and cfrA, were expressed at higher levels in the wild-type strain under iron limitation and in the fur mutant in iron-rich conditions, suggesting that they were regulated by Fur. Genes encoding a previously uncharacterized ABC transport system (Cj1660–Cj1663) also appeared to be Fur regulated, supporting a role for these genes in iron uptake. Several promoters containing consensus Fur boxes that were identified in a previous bioinformatics search appeared not to be regulated by iron or Fur, indicating that the Fur box consensus needs experimental refinement. Binding of purified Fur to the promoters upstream of the p19, CfrA and CeuB operons was verified using an electrophoretic mobility shift assay (EMSA). These results also implicated Fur as having a role in the regulation of several genes, including fumarate hydratase, that showed decreased expression in response to iron limitation. The known PerR promoters were also derepressed in the C. jejuni Fur mutant, suggesting that they might be co-regulated in response to iron and peroxide stress. These results provide new insights into the effects of iron on metabolism and oxidative stress response as well as the regulatory role of Fur.

scholarly journals Salmonella typhimurium Encodes a Putative Iron Transport System within the Centisome 63 Pathogenicity Island

1999 ◽  
Vol 67 (4) ◽  
pp. 1974-1981 ◽  
Author(s):  
Daoguo Zhou ◽  
Wolf-Dietrich Hardt ◽  
Jorge E. Galán
Keyword(s):  
Salmonella Typhimurium ◽  
Transport System ◽  
Minimal Medium ◽  
Iron Transport ◽  
Binding Protein ◽  
Pathogenicity Island ◽  
Nucleotide Composition ◽  
Growth Defect ◽  
Dependent Manner ◽  
Restricted Environment

ABSTRACT Upon entry into the host, Salmonella enterica strains are presumed to encounter an iron-restricted environment. Consequently, these bacteria have evolved a variety of often-redundant high-affinity acquisition systems to obtain iron in this restricted environment. We have identified an iron transport system that is encoded within the centisome 63 pathogenicity island of Salmonella typhimurium. The nucleotide composition of this locus is significantly different from that of the rest of this pathogenicity island, suggesting a different ancestry and a mosaic structure for this region of the S. typhimurium chromosome. This locus, designated sit, consists of four open reading frames which encode polypeptides with extensive homology to the yfe ABC iron transport system of Yersinia pestis, as well as other ABC transporters. The sitA gene encodes a putative periplasmic binding protein, sitB encodes an ATP-binding protein, and sitC and sitD encode two putative permeases (integral membrane proteins). This operon is capable of complementing the growth defect of the enterobactin-deficient Escherichia coli strain SAB11 in iron-restricted minimal medium. Transcription of the sitoperon is repressed under iron-rich growth conditions in afur-dependent manner. Introduction of a sitBCDdeletion into wild-type S. typhimuriumresulted in no apparent growth defect in either nutrient-rich or minimal medium and no measurable virulence phenotype. These results further support the existence of redundant iron uptake systems in S. enterica.

scholarly journals FbpC Is Not Essential for Iron Acquisition inNeisseria gonorrhoeae

1999 ◽  
Vol 67 (6) ◽  
pp. 3141-3145 ◽  
Author(s):  
Shite Sebastian ◽  
Caroline Attardo Genco
Keyword(s):  
Iron Transport ◽  
Iron Acquisition ◽  
Transport Systems ◽  
Northern Analysis ◽  
Pcr Analysis ◽  
Ferric Nitrate ◽  
Periplasmic Binding Protein ◽  
Reverse Transcription Pcr ◽  
Abc Transport ◽  
Insertional Inactivation

ABSTRACT The fbpABC locus of Neisseria gonorrhoeaehas been proposed to encode a periplasmic protein-dependent iron transport system. Although the function of the gonococcal FbpA protein has been well characterized and its role as a periplasmic binding protein is well defined, little is known about the function of the FbpB and FbpC proteins. To define the function of the gonococcal FbpC protein, an N. gonorrhoeae F62 fbpC mutant was constructed by insertional inactivation with the kanamycin gene. TheN. gonorrhoeae F62 fbpC mutant was observed to grow with heme, transferrin, or ferric nitrate as the sole exogenous iron source, indicating that the gonococcal FbpC protein is not absolutely required for growth with these iron sources. In previous studies we were unable to detect fbpB- orfbpC-specific transcripts by Northern analysis. Reverse transcription-PCR analysis with RNA obtained from N. gonorrhoeae F62 grown under iron-replete and -depleted conditions detected fbpA and fbpAB transcripts but failed to detect fbpC or fbpBC transcripts. These results indicate that FbpC does not play a pivotal role in iron transport in N. gonorrhoeae and suggest that additional ABC transport systems are functional in the gonococcus for the acquisition of iron.

scholarly journals Contribution of the Shigella flexneri Sit, Iuc, and Feo Iron Acquisition Systems to Iron Acquisition In Vitro and in Cultured Cells

2003 ◽  
Vol 71 (4) ◽  
pp. 1919-1928 ◽  
Author(s):  
L. J. Runyen-Janecky ◽  
S. A. Reeves ◽  
E. G. Gonzales ◽  
S. M. Payne
Keyword(s):  
Iron Transport ◽  
Cultured Cells ◽  
Iron Acquisition ◽  
Shigella Flexneri ◽  
Luria Broth ◽  
Iron Chelator ◽  
Wild Type ◽  
Cell Monolayers ◽  
Serovar Typhimurium

ABSTRACT Shigella flexneri possesses multiple iron acquisition systems, including proteins involved in the synthesis and uptake of siderophores and the Feo system for ferrous iron utilization. We identified an additional S. flexneri putative iron transport gene, sitA, in a screen for S. flexneri genes that are induced in the eukaryotic intracellular environment. sitA was present in all Shigella species and in most enteroinvasive Escherichia coli strains but not in any other E. coli isolates tested. The sit locus consists of four genes encoding a potential ABC transport system. The deduced amino acid sequence of the S. flexneri sit locus was homologous to the Salmonella enterica serovar Typhimurium Sit and Yersinia pestis Yfe systems, which mediate both manganese and iron transport. The S. flexneri sit promoter was repressed by either iron or manganese, and the iron repression was partially dependent upon Fur. A sitA::cam mutation was constructed in S. flexneri. The sitA mutant showed reduced growth, relative to the wild type, in Luria broth containing an iron chelator but formed wild-type plaques on Henle cell monolayers, indicating that the sitA mutant was able to acquire iron and/or manganese in the host cell. However, mutants defective in two of these iron acquisition systems (sitA iucD, sitA feoB, and feoB iucD) formed slightly smaller plaques on Henle cell monolayers. A strain carrying mutations in sitA, feoB, and iucD did not form plaques on Henle cell monolayers.

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