scholarly journals Iron Regulation and Pathogenicity in Erwinia chrysanthemi 3937: Role of the Fur Repressor Protein

1999 ◽  
Vol 12 (2) ◽  
pp. 119-128 ◽  
Author(s):  
Thierry Franza ◽  
Christele Sauvage ◽  
Dominique Expert
Keyword(s):  
Iron Transport ◽  
Reverse Genetics ◽  
Erwinia Chrysanthemi ◽  
Transport Systems ◽  
Iron Regulation ◽  
Iron Availability ◽  
Reading Frame ◽  
Genes Encoding ◽  
Coordinated Expression ◽  
Main Determinants

Low iron availability is a triggering signal for coordinated expression of the genes encoding pectate lyases PelB, PelC, PelD, and PelE, and chrysobactin iron transport functions, which are two main determinants of phytopathogenicity of the Erwinia chrysanthemi strain 3937. The possible implication of the ferric uptake regulation (Fur) protein in this process was investigated. The E. chrysanthemi fur gene was cloned by functional complementation of an Escherichia coli fur mutant and sequenced. The 444-bp open reading frame identified was found to code for a protein highly similar to the E. coli Fur regulator. An E. chrysanthemi fur null mutant was constructed by reverse genetics. This mutant showed altered growth capacity and reduced pathogenicity on African violets. In a fur background, transcriptional lacZ fusions to genes belonging to the E. chrysanthemi high affinity iron transport systems were constitutively expressed. Transcription of the pelA, pelD, and pelE genes was analyzed, using fusions to the uidA reporter gene. Iron availability and a fur mutation did not influence the expression of pelA. In the presence of iron, pelD and pelE transcription levels were higher in the fur mutant than in the parental strain. Furthermore, iron deficiency stimulated the expression of both fusions in the fur mutant. These findings indicate that, in E. chrysanthemi 3937, (i) Fur negatively controls iron transport and genes encoding PelD and PelE, and (ii) additional factor(s) mediate iron regulation of the pel genes.

scholarly journals Vibrio Iron Transport: Evolutionary Adaptation to Life in Multiple Environments

2015 ◽  
Vol 80 (1) ◽  
pp. 69-90 ◽  
Author(s):  
Shelley M. Payne ◽  
Alexandra R. Mey ◽  
Elizabeth E. Wyckoff
Keyword(s):  
Regulatory Networks ◽  
Iron Transport ◽  
Horizontal Transmission ◽  
Essential Element ◽  
Transport Systems ◽  
Iron Binding ◽  
Content Type ◽  
High Affinity ◽  
Wide Range ◽  
Genes Encoding

SUMMARYIron is an essential element forVibriospp., but the acquisition of iron is complicated by its tendency to form insoluble ferric complexes in nature and its association with high-affinity iron-binding proteins in the host. Vibrios occupy a variety of different niches, and each of these niches presents particular challenges for acquiring sufficient iron.Vibriospecies have evolved a wide array of iron transport systems that allow the bacteria to compete for this essential element in each of its habitats. These systems include the secretion and uptake of high-affinity iron-binding compounds (siderophores) as well as transport systems for iron bound to host complexes. Transporters for ferric and ferrous iron not complexed to siderophores are also common toVibriospecies. Some of the genes encoding these systems show evidence of horizontal transmission, and the ability to acquire and incorporate additional iron transport systems may have allowedVibriospecies to more rapidly adapt to new environmental niches. While too little iron prevents growth of the bacteria, too much can be lethal. The appropriate balance is maintained in vibrios through complex regulatory networks involving transcriptional repressors and activators and small RNAs (sRNAs) that act posttranscriptionally. Examination of the number and variety of iron transport systems found inVibriospp. offers insights into how this group of bacteria has adapted to such a wide range of habitats.

scholarly journals Coupling of Iron Assimilation and Pectinolysis in Erwinia chrysanthemi 3937

2002 ◽  
Vol 15 (11) ◽  
pp. 1181-1191 ◽  
Author(s):  
Thierry Franza ◽  
Isabelle Michaud-Soret ◽  
Pierrette Piquerel ◽  
Dominique Expert
Keyword(s):  
Iron Transport ◽  
Molecular Mechanisms ◽  
Constitutive Expression ◽  
Erwinia Chrysanthemi ◽  
Activation Mechanism ◽  
Receptor Protein ◽  
Virulence Determinants ◽  
Pectate Lyases ◽  
Iron Assimilation ◽  
Genes Encoding

Two major virulence determinants of the plant-pathogenic enterobacterium Erwinia chrysanthemi strain 3937 are the production of pectate lyase enzymes that degrade plant cell walls and expression of two high-affinity iron uptake systems mediated by two structurally unrelated siderophores, chrysobactin and achromobactin. Low iron availability is a signal that triggers transcription of the genes encoding pectate lyases PelD and PelE as well as that of genes involved in iron transport. This metalloregulation is mediated by the transcriptional repressor Fur. In this study, we analyzed the molecular mechanisms of this control. We purified the Erwinia chrysanthemi Fur protein. Band shift assays showed that Fur specifically binds in vitro to the regulatory regions of the genes encoding the ferrichrysobactin outer membrane receptor Fct and the pectate lyases PelD and PelE. We identified the Fur-binding sites of these promoter regions by performing DNase I footprinting experiments. From these data, we propose that Fur could inhibit the activation of the pelD and pelE genes by the cAMP receptor protein CRP according to an anti-activation mechanism. To identify other possible effectors involved in this control, we screened a bank of insertion mutants for an increase in transcriptional activity of pelD and fct genes in response to iron limitation. We isolated a mutant affected in the kdgK gene encoding the 2-keto-3-deoxygluconate (KDG) kinase, an enzyme involved in pectin catabolism. The growth of this mutant in the presence of pectic compounds led to a constitutive expression of iron transport genes as well as complete derepression of the pectinolysis genes. This effect was caused by intracellular accumulation of KDG. However, the derepression of iron transport genes by KDG does not involve the KdgR regulator of pectinolysis genes, which uses KDG as inducer. Thus, in Erwinia chrysanthemi, iron depletion or presence of KDG induces transcription of the genes involved in iron assimilation and pectinolysis. These important pathogenicity functions are coregulated by responding to common signals encountered in planta.

scholarly journals Processing of Open Reading Frame 1a Replicase Proteins nsp7 to nsp10 in Murine Hepatitis Virus Strain A59 Replication

2007 ◽  
Vol 81 (19) ◽  
pp. 10280-10291 ◽  
Author(s):  
Damon J. Deming ◽  
Rachel L. Graham ◽  
Mark R. Denison ◽  
Ralph S. Baric
Keyword(s):  
Reverse Genetics ◽  
Hepatitis Virus ◽  
Proteolytic Processing ◽  
Mutant Virus ◽  
Open Reading Frame ◽  
Cleavage Sites ◽  
Nonstructural Proteins ◽  
Murine Hepatitis Virus ◽  
Reading Frame ◽  
Genes Encoding

ABSTRACT Coronaviruses express open reading frame 1a (ORF1a) and ORF1b polyproteins from which 16 nonstructural proteins (nsp) are derived. The highly conserved region at the carboxy terminus of ORF1a is processed by the nsp5 proteinase (Mpro) into mature products, including nsp7, nsp8, nsp9, and nsp10, proteins with predicted or identified activities involved in RNA synthesis. Although continuous translation and proteolytic processing of ORF1ab by Mpro is required for replication, it is unknown whether specific cleavage events within the polyprotein are dispensable. We determined the requirement for the nsp7 to nsp10 proteins and their processing during murine hepatitis virus (MHV) replication. Through use of an MHV reverse genetics system, in-frame deletions of the coding sequences for nsp7 to nsp10, or ablation of their flanking Mpro cleavage sites, were made and the effects upon replication were determined. Viable viruses were characterized by analysis of Mpro processing, RNA transcription, and growth fitness. Deletion of any of the regions encoding nsp7 to nsp10 was lethal. Disruption of the cleavage sites was lethal with the exception of that of the nsp9-nsp10 site, which resulted in a mutant virus with attenuated replication. Passage of the attenuated nsp9-nsp10 cleavage mutant increased fitness to near-wild-type kinetics without reversion to a virus capable of processing nsp9-nsp10. We also confirmed the presence of a second cleavage site between nsp7 and nsp8. In order to determine whether a distinct function could be attributed to preprocessed forms of the polyprotein, including nsp7 to nsp10, the genes encoding nsp7 and nsp8 were rearranged. The mutant virus was not viable, suggesting that the uncleaved protein may be essential for replication or proteolytic processing.

scholarly journals Essential Role of Superoxide Dismutase on the Pathogenicity of Erwinia chrysanthemi Strain 3937

2001 ◽  
Vol 14 (6) ◽  
pp. 758-767 ◽  
Author(s):  
Renata Santos ◽  
Thierry Franza ◽  
Marie-Lyne Laporte ◽  
Christele Sauvage ◽  
Danièle Touati ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Superoxide Anion ◽  
Type Strain ◽  
Reverse Genetics ◽  
Wild Type Strain ◽  
Erwinia Chrysanthemi ◽  
Wild Type ◽  
Reading Frame ◽  
E Coli ◽  
Oxidative Damages

The sodA gene from Erwinia chrysanthemi strain 3937 was cloned by functional complementation of an Escherichia coli sodA sodB mutant and sequenced. We identified a 639-bp open reading frame, which encodes a protein that is 85% identical to the E. coli manganese-containing superoxide dismutase MnSOD. Promoter elements of this gene were identified by transcriptional mapping experiments. We constructed an E. chrysanthemi ΔsodA mutant by reverse genetics. The ΔsodA mutation resulted in the absence of a cytoplasmic SOD, which displays the same characteristics as those of MnSOD. The ΔsodA mutant was more sensitive to paraquat than the wild-type strain. This mutant could macerate potato tubers, similar to the wild-type strain. In contrast, when inoculated on African violets, the mutant produced, at most, only small necrotic lesions. If the inoculum was supplemented with the superoxide anion-scavenging metalloporphyrin MnTMPyP or purified SOD and catalase, the ΔsodA mutant was able to macerate the inoculated zone. Generation of superoxide anion by African violet leaves inoculated with E. chrysanthemi was demonstrated with nitroblue tetrazolium as an indicator. Therefore, at the onset of infection, E. chrysanthemi cells encounter an oxidative environment and require active protective systems against oxidative damages such as MnSOD to overcome these types of conditions.

scholarly journals RegA, an AraC-Like Protein, Is a Global Transcriptional Regulator That Controls Virulence Gene Expression in Citrobacter rodentium

2008 ◽  
Vol 76 (11) ◽  
pp. 5247-5256 ◽  
Author(s):  
Emily Hart ◽  
Ji Yang ◽  
Marija Tauschek ◽  
Michelle Kelly ◽  
Matthew J. Wakefield ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Virulence Gene ◽  
Virulence Determinants ◽  
Intestinal Colonization ◽  
Citrobacter Rodentium ◽  
Promoter Regions ◽  
Reading Frame ◽  
Virulence Gene Expression ◽  
Genes Encoding ◽  
Colonization Factors

ABSTRACT Citrobacter rodentium is an attaching and effacing pathogen which causes transmissible colonic hyperplasia in mice. Infection with C. rodentium serves as a model for infection of humans with enteropathogenic and enterohemorrhagic Escherichia coli. To identify novel colonization factors of C. rodentium, we screened a signature-tagged mutant library of C. rodentium in mice. One noncolonizing mutant had a single transposon insertion in an open reading frame (ORF) which we designated regA because of its homology to genes encoding members of the AraC family of transcriptional regulators. Deletion of regA in C. rodentium resulted in markedly reduced colonization of the mouse intestine. Examination of lacZ transcriptional fusions using promoter regions of known and putative virulence-associated genes of C. rodentium revealed that RegA strongly stimulated transcription of two newly identified genes located close to regA, which we designated adcA and kfcC. The cloned adcA gene conferred autoaggregation and adherence to mammalian cells to E. coli strain DH5α, and a kfc mutation led to a reduction in the duration of intestinal colonization, but the kfc mutant was far less attenuated than the regA mutant. These results indicated that other genes of C. rodentium whose expression required activation by RegA were required for colonization. Microarray analysis revealed a number of RegA-regulated ORFs encoding proteins homologous to known colonization factors. Transcription of these putative virulence determinants was activated by RegA only in the presence of sodium bicarbonate. Taken together, these results show that RegA is a global regulator of virulence in C. rodentium which activates factors that are required for intestinal colonization.

scholarly journals Infection with Mycobacterium aviumDifferentially Regulates the Expression of Iron Transport Protein mRNA in Murine Peritoneal Macrophages

2001 ◽  
Vol 69 (11) ◽  
pp. 6618-6624 ◽  
Author(s):  
Wangjian Zhong ◽  
William P. Lafuse ◽  
Bruce S. Zwilling
Keyword(s):  
Host Defense ◽  
Transferrin Receptor ◽  
Iron Transport ◽  
Peritoneal Macrophages ◽  
Natural Resistance ◽  
Intracellular Pathogens ◽  
Mrna Levels ◽  
Iron Availability ◽  
Iron Transporter ◽  
Murine Peritoneal Macrophages

ABSTRACT Iron is an important element for the growth of microorganisms as well as in the defense of the host by serving as a catalyst for the generation of free radicals via the Fenton/Haber-Weiss reactions. The iron transporter natural resistance-associated macrophage protein 1 (Nramp1) confers resistance to the growth of a variety of intracellular pathogens including Mycobacterium avium. Recently several other proteins that are involved in iron transport, including the highly homologous iron transporter Nramp2 and the transferrin receptor-associated protein HFE (hereditary hemochromatosis protein), have been described. The relationship of these proteins to host defense and to the growth of intracellular pathogens is not known. Here, we report that infection with M. avium differentially regulates mRNA expression of the proteins associated with iron transport in murine peritoneal macrophages. Both Nramp1 and Nramp2 mRNA levels increase following infection, while the expression of transferrin receptor mRNA decreases. The level of expression of HFE mRNA remains unchanged. The difference in the expression of the mRNA of these proteins following infection or cytokine stimulation suggests that they may play an important role in host defense by maintaining a delicate balance between iron availability for host defense and at the same time limiting iron availability for microbial growth.

scholarly journals Desketoneoenactin-Siderophore Conjugates for Candida: Evidence of Iron Transport-Dependent Species Selectivity

2005 ◽  
Vol 49 (1) ◽  
pp. 241-248 ◽  
Author(s):  
Geneviève Bernier ◽  
Vinay Girijavallabhan ◽  
Aaron Murray ◽  
Noormohamed Niyaz ◽  
Pingyu Ding ◽  
...  
Keyword(s):  
Inhibitory Activity ◽  
Parent Strain ◽  
Iron Transport ◽  
Growth Promotion ◽  
Common Mechanism ◽  
Iron Availability ◽  
Species Selectivity ◽  
Drug Conjugates ◽  
Siderophore Transporter ◽  
Selective Activity

ABSTRACT We investigated the inhibitory activity of synthetic isocyanurate-based as well as linear mono- and trihydroxamate siderophore-drug conjugates against Candida spp. The conjugated drug was 13C-desketoneoenactin (DE). The MICs of siderophore-drug conjugates were determined in the absence and presence of 2,2′-dipyridyl to restrict iron availability. The ability of various siderophore types to promote growth in an iron-restricted medium was also assayed. Addition of a siderophore portion to the drug strongly impaired the inhibitory activity of DE. However, the activity of the drug conjugates was increased by up to 16-fold in iron-depleted medium for species having their growth strongly promoted by most hydroxamate-type siderophores (C. albicans, C. stellatoidea, and C. pseudotropicalis). The uptake of 55Fe from ferrichrome and from two siderophore-drug conjugates was improved when C. albicans cells were grown in a low-iron medium. In the same assay, unlabeled ferrichrome was able to compete with the uptake of 55Fe from both conjugates, indicating a common mechanism of uptake. A C. albicans strain lacking the siderophore transporter CaSit1/CaArn1 was not able to use ferrichrome or the synthetic ornithine-based trihydroxamate siderophore for growth promotion and was much less susceptible to the siderophore-drug conjugates than its isogenic parent strain. In summary, the ability of some Candida spp. to use ferrichrome-like siderophores for growth promotion explains the selective activity of hydroxamate-drug conjugates, and this activity seems to be related to the presence, in C. albicans, of the siderophore transporter CaSit1/CaArn1. New conjugate designs are necessary to fully restore or improve the initial DE activity.

scholarly journals Genes Essential to Iron Transport in the Cyanobacterium Synechocystis sp. Strain PCC 6803

2001 ◽  
Vol 183 (9) ◽  
pp. 2779-2784 ◽  
Author(s):  
Hirokazu Katoh ◽  
Natsu Hagino ◽  
Arthur R. Grossman ◽  
Teruo Ogawa
Keyword(s):  
Iron Uptake ◽  
Iron Transport ◽  
Ferric Iron ◽  
Iron Acquisition ◽  
Complete Medium ◽  
Iron Starvation ◽  
Transporter Family ◽  
Genes Encoding ◽  
In Cells ◽  
Pcc 6803

ABSTRACT Genes encoding polypeptides of an ATP binding cassette (ABC)-type ferric iron transporter that plays a major role in iron acquisition inSynechocystis sp. strain PCC 6803 were identified. These genes are slr1295, slr0513, slr0327, and recently reportedsll1878 (Katoh et al., J. Bacteriol. 182:6523–6524, 2000) and were designated futA1, futA2, futB, andfutC, respectively, for their involvement in ferric iron uptake. Inactivation of these genes individually or futA1and futA2 together greatly reduced the activity of ferric iron uptake in cells grown in complete medium or iron-deprived medium. All the fut genes are expressed in cells grown in complete medium, and expression was enhanced by iron starvation. ThefutA1 and futA2 genes appear to encode periplasmic proteins that play a redundant role in iron binding. The deduced products of futB and futC genes contain nucleotide-binding motifs and belong to the ABC transporter family of inner-membrane-bound and membrane-associated proteins, respectively. These results and sequence similarities among the four genes suggest that the Fut system is related to the Sfu/Fbp family of iron transporters. Inactivation of slr1392, a homologue offeoB in Escherichia coli, greatly reduced the activity of ferrous iron transport. This system is induced by intracellular low iron concentrations that are achieved in cells exposed to iron-free medium or in the fut-less mutants grown in complete medium.

scholarly journals The Utility of Iron Chelators in the Management of Inflammatory Disorders

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
C. Lehmann ◽  
S. Islam ◽  
S. Jarosch ◽  
J. Zhou ◽  
D. Hoskin ◽  
...  
Keyword(s):  
Inflammatory Diseases ◽  
Iron Chelation ◽  
Iron Regulation ◽  
Human Organism ◽  
Iron Availability ◽  
Pathological Conditions ◽  
Reasonable Approach ◽  
Potential Impact ◽  
Pharmaceutical Agents

Since iron can contribute to detrimental radical generating processes through the Fenton and Haber-Weiss reactions, it seems to be a reasonable approach to modulate iron-related pathways in inflammation. In the human organism a counterregulatory reduction in iron availability is observed during inflammatory diseases. Under pathological conditions with reduced or increased baseline iron levels different consequences regarding protection or susceptibility to inflammation have to be considered. Given the role of iron in development of inflammatory diseases, pharmaceutical agents targeting this pathway promise to improve the clinical outcome. The objective of this review is to highlight the mechanisms of iron regulation and iron chelation, and to demonstrate the potential impact of this strategy in the management of several acute and chronic inflammatory diseases, including cancer.

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