Identification of the Iron-Responsive Genes of
            <i>Neisseria gonorrhoeae</i>
            by Microarray Analysis in Defined Medium

Ducey, Thomas F.; Carson, Matthew B.; Orvis, Joshua; Stintzi, Alain; Dyer, David W.

doi:10.1128/jb.187.14.4865-4874.2005

Cited by 90 publications

(128 citation statements)

References 81 publications

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“…Increased expression of genes encoding ribosomal proteins and secretion proteins in response to iron may contribute to the high-efficiency protein synthesis and subsequent protein transport across the membrane in response to iron. Our results are also in agreement with recent studies by Ducey et al (13), which suggest that several gonococcal genes, including genes encoding ribosomal proteins, are upregulated under iron-replete growth conditions.…”

supporting

confidence: 83%

“…Although these genes were not identified in a very recently published study on the N. meningitidis fur and iron regulon (5), this could be attributed to variations in experimental design, i.e., the media used and time points chosen for analysis of gene expression. Our results, however, are supported by recent studies of N. gonorrhoeae wherein expression of the protein secretion secY and secE genes and several ribosomal genes were reported to be increased during growth under iron-replete conditions (13), although the role of Fur in the regulation of these genes was not examined.…”

supporting

confidence: 50%

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Expression of the Iron-ActivatednspAandsecYGenes inNeisseria meningitidisGroup B by Fur-Dependent and -Independent Mechanisms

et al. 2007

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Our whole-genome microarray studies of Neisseria meningitidis MC58 previously identified a set of 153 genes whose transcription was activated during growth in iron. In this study, Fur-mediated regulation of the iron-activated nspA gene was confirmed, whereas iron-activated regulation of the secY gene was demonstrated to be Fur independent. Analysis of the Fur binding sequences in the nspA gene and an additional iron-activated and Fur-regulated gene identified a hexameric (G/T)ATAAT unit in the operator regions of these genes similar to that observed in Fur-and iron-repressed genes. These studies indicate that the expression of the ironactivated nspA and secY genes in N. meningitidis occur by Fur-dependent and -independent mechanisms, respectively.It is well established that the iron-responsive regulatory protein Fur functions as a repressor of gene transcription in several microorganisms. In its most basic state, Fur forms a dimer together with divalent cations, such as ferrous iron, and binds to a consensus sequence (the Fur box) that overlaps the promoters of iron-regulated genes to prevent their transcription. Recent studies indicate that in some organisms, Fur may also function as a positive regulator of gene transcription, together with iron (8,(9)(10)(11)(12)24), although the mechanism of iron activation by Fur is not well elucidated. Our recent studies of N. meningitidis group B, using a combination of microarray technology, computational analysis, and in vitro binding studies, revealed that a large number of genes are activated during growth in the presence of iron and that a number of these iron-activated genes have putative Fur-binding sequences to which Fur was demonstrated to bind (17). However, the biological significance of Fur binding to the operator regions of these genes has not been defined, as an N. meningitidis fur mutant had not been constructed at the time of that study.Of interest within the group of iron-activated genes under the potential control of Fur were candidate genes involved in the virulence potential of N. meningitidis, including the nspA (NMB0663) (1, 21) and secY (NMB0162) (18, 28) genes. Neisserial surface protein A (NspA) is an 18.6-kDa membrane protein of unknown function that was first described to confer protection against meningococcal infection in animal models of infection (1,21,22). NspA is highly conserved and expressed by all N. meningitidis strains tested (22,25). Recent studies indicate that conserved epitopes of the NspA protein confer protection against N. meningitidis serogroup B challenge in a mouse model of meningococcal infection (26). The N. meningitidis secY gene encodes a putative preprotein translocase (SecY) whose homolog in Escherichia coli has been studied extensively; in E. coli, it functions as an essential component of the protein translocation machinery of the cytoplasmic membrane. Sec-dependent protein secretion in the pathogenic Neisseria has been reported (18, 28); however, the function of the N. meningitidis SecY protein is not known, nor has ...

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supporting

confidence: 83%

supporting

confidence: 50%

Expression of the Iron-ActivatednspAandsecYGenes inNeisseria meningitidisGroup B by Fur-Dependent and -Independent Mechanisms

et al. 2007

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“…The expression of the majority of iron binding proteins is regulated by Fur in N. gonorrhoeae (23) in a manner similar to that of several other bacteria (78). The Fur regulon of N. gonorrhoeae includes the iron-repressible genes tbpB, lbpB, tonB, and fbpA, which are associated with iron sequestration under iron-limiting conditions (74,86). It has proved more difficult to identify genes under Fur control that are activated in response to high levels of iron.…”

Section: Iron Sequestrationmentioning

confidence: 99%

“…Microarray analysis has indicated that 203 genes are regulated in response to iron in N. gonorrhoeae: 109 genes are upregulated and 94 genes are downregulated by iron deprivation (74). Based on analysis of putative promoter regions, 50 operons were predicted to be directly regulated by Fur (74).…”

Section: Iron Sequestrationmentioning

confidence: 99%

Defenses against Oxidative Stress inNeisseria gonorrhoeae: a System Tailored for a Challenging Environment

Seib

Kidd

et al. 2006

Microbiol Mol Biol Rev

125

174

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SUMMARY Neisseria gonorrhoeae is a host-adapted pathogen that colonizes primarily the human genitourinary tract. This bacterium encounters reactive oxygen and reactive nitrogen species as a consequence of localized inflammatory responses in the urethra of males and endocervix of females and also of the activity of commensal lactobacilli in the vaginal flora. This review describes recent advances in the understanding of defense systems against oxidative stress in N. gonorrhoeae and shows that while some of its defenses have similarities to the paradigm established with Escherichia coli, there are also some key differences. These differences include the presence of a defense system against superoxide based on manganese ions and a glutathione-dependent system for defense against nitric oxide which is under the control of a novel MerR-like transcriptional regulator. An understanding of the defenses against oxidative stress in N. gonorrhoeae and their regulation may provide new insights into the ways in which this bacterium survives challenges from polymorphonuclear leukocytes and urogenital epithelial cells.

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“…Such rapid magnetite formation has also been observed in M. gryphiswaldense (26). Transmission electron microscopy confirmed the absence of magnetosomes in cells grown in 0.1 M iron.To relate the robust iron uptake to the corresponding gene expressions of M. magneticum AMB-1 cultured under different iron conditions, transcription profiles were obtained by standard DNA microarray (8,18,19). The sequence of each of the 4,492 genes obtained from M. magneticum AMB-1 (15), representing ϳ99% of the total protein-coding capacity of the whole genome sequence, was determined and synthesized from the 60-mer region of minimal homology to other open reading frames analyzed with the BLAST program.…”

mentioning

confidence: 99%

Global Gene Expression Analysis of Iron-Inducible Genes in Magnetospirillum magneticum AMB-1

et al. 2006

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Iron uptake systems were identified by global expression profiling of Magnetospirillum magneticum AMB-1. feo, tpd, and ftr, which encode ferrous iron transporters, were up-regulated under iron-rich conditions. The concomitant rapid iron uptake and magnetite formation suggest that these uptake systems serve as iron supply lines for magnetosome synthesis.Iron is crucial in microbial metabolism. It exists in two redox states: the reduced Fe 2ϩ soluble ferrous state and the oxidized Fe 3ϩ ferric form, which is extremely insoluble (1). In magnetotactic bacteria, the formation of highly organized membranebound intracellular magnetites (Fe 3 O 4 ) or greigites (Fe 3 S 4 ) requires the acquisition of a large amount of iron several orders of magnitude greater than that required by Escherichia coli (5). Because of the large amount of iron to be transported, complex iron uptake systems that differ from known transport mechanisms in other microorganisms are expected to be operating in magnetotactic bacteria. Exceptional progress has been made in the isolation and characterization of functional genes and proteins involved in magnetosome synthesis (2,11,13,21,24), but at present, specific iron transport systems remain unidentified in magnetotactic bacteria.Here we report the identification of iron uptake systems by global expression profiling of the magnetotactic bacterium Magnetospirillum magneticum AMB-1 grown under iron-rich and iron-deficient conditions. Our results indicate that despite the unusual high-iron requirement of M. magneticum AMB-1, it utilizes robust but simple iron uptake systems similar to those of other gram-negative bacteria. This robust ferrous iron uptake suggests a significant contribution to magnetite synthesis. This study is the first to identify specific iron uptake systems in the complex iron metabolism of magnetotactic bacteria. The data presented here may facilitate future studies on the mechanism of magnetosome formation.To monitor iron uptake and magnetite formation, M. magneticum AMB-1 (ATCC 700264) was grown at 25°C under microaerobic conditions by sparging argon gas for 10 min into 500 ml of MSGM medium as previously described (5), with various iron concentrations of 0.1 to 300 M. All iron measurements were performed by atomic absorbance spectrophotometry. Extracellular iron concentrations were measured at different time points in cell-free culture supernatants. For intracellular iron measurements, cells were disrupted by lysozyme treatment (20) and ultracentrifuged at 100,000 ϫ g to separate the insoluble (magnetites) and soluble iron fractions.Iron was rapidly taken up in iron-rich cultures, and a corresponding increase of intracellular iron was observed within 10 min (Fig. 1A). Up to 70% of the initial iron concentration of the medium was taken up, and intracellular iron increased to 5,000 nmol/10 9 cells after 60 min. Insoluble iron in the cytoplasm, which mostly included magnetites, also increased within 10 min (Fig. 1B). These data indicate that the external iron was rapidly assimilate...

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Identification of the Iron-Responsive Genes of Neisseria gonorrhoeae by Microarray Analysis in Defined Medium

Cited by 90 publications

References 81 publications

Expression of the Iron-ActivatednspAandsecYGenes inNeisseria meningitidisGroup B by Fur-Dependent and -Independent Mechanisms

Expression of the Iron-ActivatednspAandsecYGenes inNeisseria meningitidisGroup B by Fur-Dependent and -Independent Mechanisms

Defenses against Oxidative Stress inNeisseria gonorrhoeae: a System Tailored for a Challenging Environment

Global Gene Expression Analysis of Iron-Inducible Genes in Magnetospirillum magneticum AMB-1

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