Comparative and Functional Genomic Analyses of Iron Transport and Regulation in Leptospira spp.

ABSTRACT The spirochetes of the Leptospira genus contain saprophytic and pathogenic members, the latter being responsible for leptospirosis. Despite the recent sequencing of the genome of the pathogen L. interrogans, the slow growth of these bacteria, their virulence in humans, and a lack of genetic tools make it difficult to work with these pathogens. In contrast, the development of numerous genetic tools for the saprophyte L. biflexa enables its use as a model bacterium. Leptospira spp. require iron for growth. In this work, we show that Leptospira spp. can acquire iron from different sources, including siderophores. A comparative genome analysis of iron uptake systems and their regulation in the saprophyte L. biflexa and the pathogen L. interrogans is presented in this study. Our data indicated that, for instance, L. biflexa and L. interrogans contain 8 and 12 genes, respectively, whose products share homology with proteins that have been shown to be TonB-dependent receptors. We show that some genes involved in iron uptake were differentially expressed in response to iron. In addition, we were able to disrupt several putative genes involved in iron acquisition systems or iron regulation in L. biflexa. Comparative genomics, in combination with gene inactivation, gives us significant functional information on iron homeostasis in Leptospira spp.

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

Journal of Bacteriology ◽

10.1128/jb.183.9.2779-2784.2001 ◽

2001 ◽

Vol 183 (9) ◽

pp. 2779-2784 ◽

Cited By ~ 135

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.

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Iron homeostasis: new tales from the crypt

Blood ◽

10.1182/blood.v96.13.4020 ◽

2000 ◽

Vol 96 (13) ◽

pp. 4020-4027 ◽

Cited By ~ 106

Author(s):

Cindy N. Roy ◽

Caroline A. Enns

Keyword(s):

Iron Uptake ◽

Iron Transport ◽

Iron Homeostasis ◽

Molecular Mechanisms ◽

Hereditary Hemochromatosis ◽

The Body ◽

Regulatory Proteins ◽

Iron Regulatory Proteins ◽

Duodenal Epithelium ◽

Related Proteins

Abstract The enterocyte is a highly specialized cell of the duodenal epithelium that coordinates iron uptake and transport into the body. Until recently, the molecular mechanisms underlying iron absorption and iron homeostasis have remained a mystery. This review focuses on the proteins and regulatory mechanisms known to be present in the enterocyte precursor cell and in the mature enterocyte. The recent cloning of a basolateral iron transporter and investigations into its regulation provide new insights into possible mechanisms for iron transport and homeostasis. The roles of proteins such as iron regulatory proteins, the hereditary hemochromatosis protein (HFE)–transferrin receptor complex, and hephaestin in regulating this transporter and in regulating iron transport across the intestinal epithelium are discussed. A speculative, but testable, model for the maintenance of iron homeostasis, which incorporates the changes in the iron-related proteins associated with the life cycle of the enterocyte as it journeys from the crypt to the tip of the villous is proposed.

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Dopamine Is a Siderophore-Like Iron Chelator That PromotesSalmonella entericaSerovar Typhimurium Virulence in Mice

mBio ◽

10.1128/mbio.02624-18 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 7

Author(s):

Stefanie Dichtl ◽

Egon Demetz ◽

David Haschka ◽

Piotr Tymoszuk ◽

Verena Petzer ◽

...

Keyword(s):

Bacterial Growth ◽

Iron Uptake ◽

Iron Homeostasis ◽

Iron Acquisition ◽

Lipocalin 2 ◽

Intracellular Iron ◽

Content Type ◽

Hepcidin Expression

ABSTRACTWe have recently shown that the catecholamine dopamine regulates cellular iron homeostasis in macrophages. As iron is an essential nutrient for microbes, and intracellular iron availability affects the growth of intracellular bacteria, we studied whether dopamine administration impacts the course ofSalmonellainfections. Dopamine was found to promote the growth ofSalmonellaboth in culture and within bone marrow-derived macrophages, which was dependent on increased bacterial iron acquisition. Dopamine administration to mice infected withSalmonella entericaserovar Typhimurium resulted in significantly increased bacterial burdens in liver and spleen, as well as reduced survival. The promotion of bacterial growth by dopamine was independent of the siderophore-binding host peptide lipocalin-2. Rather, dopamine enhancement of iron uptake requires both the histidine sensor kinase QseC and bacterial iron transporters, in particular SitABCD, and may also involve the increased expression of bacterial iron uptake genes. Deletion or pharmacological blockade of QseC reduced but did not abolish the growth-promoting effects of dopamine. Dopamine also modulated systemic iron homeostasis by increasing hepcidin expression and depleting macrophages of the iron exporter ferroportin, which enhanced intracellular bacterial growth.Salmonellalacking all central iron uptake pathways failed to benefit from dopamine treatment. These observations are potentially relevant to critically ill patients, in whom the pharmacological administration of catecholamines to improve circulatory performance may exacerbate the course of infection with siderophilic bacteria.IMPORTANCEHere we show that dopamine increases bacterial iron incorporation and promotesSalmonellaTyphimurium growth bothin vitroandin vivo. These observations suggest the potential hazards of pharmacological catecholamine administration in patients with bacterial sepsis but also suggest that the inhibition of bacterial iron acquisition might provide a useful approach to antimicrobial therapy.

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The Role of SreA-Mediated Iron Regulation in Maintaining Epichloë festucae–Lolium perenne Symbioses

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-03-19-0060-r ◽

2019 ◽

Vol 32 (10) ◽

pp. 1324-1335 ◽

Cited By ~ 3

Author(s):

Natasha T. Forester ◽

Geoffrey A. Lane ◽

Catherine M. McKenzie ◽

Iain L. Lamont ◽

Linda J. Johnson

Keyword(s):

Iron Uptake ◽

Iron Homeostasis ◽

Iron Acquisition ◽

Functional Characterization ◽

Fungal Growth ◽

Hyphal Growth ◽

Epichloë Festucae ◽

Gradual Loss ◽

Growth Assay ◽

Iron Management

In ascomycetes and basidiomycetes, iron-responsive GATA-type transcriptional repressors are involved in regulating iron homeostasis, notably to prevent iron toxicity through control of iron uptake. To date, it has been unknown whether this iron regulator contributes toward mutualistic endosymbiosis of microbes with plants, a system where the endophyte must function within the constraints of an in-host existence, including a dependency on the host for nutrient acquisition. Functional characterization of one such protein, SreA from Epichloë festucae, a fungal endosymbiont of cool-season grasses, indicates that regulation of iron homeostasis processes is important for symbiotic maintenance. The deletion of the sreA gene (ΔsreA) led to iron-dependent aberrant hyphal growth and the gradual loss of endophyte hyphae from perennial ryegrass. SreA negatively regulates the siderophore biosynthesis and high-affinity iron uptake systems of E. festucae, similar to other fungi, resulting in iron accumulation in mutants. Our evidence suggests that SreA is involved in the processes that moderate Epichloë iron acquisition from the plant apoplast, because overharvesting of iron in ΔsreA mutants was detected as premature chlorosis of the host using a hydroponic plant growth assay. E. festucae appears to have a tightly regulated iron management system, involving SreA that balances endophyte growth with its survival and prevents overcompetition with the host for iron in the intercellular niche, thus promoting mutualistic associations. Mutations that interfere with Epichloë iron management negatively affect iron-dependent fungal growth and destabilize mutualistic Epichloë –ryegrass associations.

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Secreted Pyomelanin of Legionella pneumophila Promotes Bacterial Iron Uptake and Growth under Iron-Limiting Conditions

Infection and Immunity ◽

10.1128/iai.00858-13 ◽

2013 ◽

Vol 81 (11) ◽

pp. 4182-4191 ◽

Cited By ~ 33

Author(s):

Huaixin Zheng ◽

Christa H. Chatfield ◽

Mark R. Liles ◽

Nicholas P. Cianciotto

Keyword(s):

Legionella Pneumophila ◽

Ferrous Iron ◽

Iron Uptake ◽

Iron Transport ◽

Ferric Iron ◽

Iron Acquisition ◽

Ferric Hydroxide ◽

Supernatant Fraction ◽

Content Type ◽

Ferrous Iron Transport

ABSTRACTIron acquisition is critical to the growth and virulence ofLegionella pneumophila. Previously, we found thatL. pneumophilauses both a ferrisiderophore pathway and ferrous iron transport to obtain iron. We now report that two molecules secreted byL. pneumophila, homogentisic acid (HGA) and its polymerized variant (HGA-melanin, a pyomelanin), are able to directly mediate the reduction of various ferric iron salts. Furthermore, HGA, synthetic HGA-melanin, and HGA-melanin derived from bacterial supernatants enhanced the ability ofL. pneumophilaand other species ofLegionellato take up radiolabeled iron. Enhanced iron uptake was not observed with a ferrous iron transport mutant. Thus, HGA and HGA-melanin mediate ferric iron reduction, with the resulting ferrous iron being available to the bacterium for uptake. Upon further testing ofL. pneumophilaculture supernatants, we found that significant amounts of ferric and ferrous iron were associated with secreted HGA-melanin. Importantly, a pyomelanin-containing fraction obtained from a wild-type culture supernatant was able to stimulate the growth of iron-starved legionellae. That the corresponding supernatant fraction obtained from a nonpigmented mutant culture did not stimulate growth demonstrated that HGA-melanin is able to both promote iron uptake and enhance growth under iron-limiting conditions. Indicative of a complementary role in iron acquisition, HGA-melanin levels were inversely related to the levels of siderophore activity. Compatible with a role in the ecology and pathogenesis ofL. pneumophila, HGA and HGA-melanin were effective at reducing and releasing iron from both insoluble ferric hydroxide and the mammalian iron chelates ferritin and transferrin.

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Iron homeostasis: new tales from the crypt

Blood ◽

10.1182/blood.v96.13.4020.h8004020_4020_4027 ◽

2000 ◽

Vol 96 (13) ◽

pp. 4020-4027 ◽

Cited By ~ 1

Author(s):

Cindy N. Roy ◽

Caroline A. Enns

Keyword(s):

Iron Uptake ◽

Iron Transport ◽

Iron Homeostasis ◽

Molecular Mechanisms ◽

Hereditary Hemochromatosis ◽

The Body ◽

Regulatory Proteins ◽

Iron Regulatory Proteins ◽

Duodenal Epithelium ◽

Related Proteins

The enterocyte is a highly specialized cell of the duodenal epithelium that coordinates iron uptake and transport into the body. Until recently, the molecular mechanisms underlying iron absorption and iron homeostasis have remained a mystery. This review focuses on the proteins and regulatory mechanisms known to be present in the enterocyte precursor cell and in the mature enterocyte. The recent cloning of a basolateral iron transporter and investigations into its regulation provide new insights into possible mechanisms for iron transport and homeostasis. The roles of proteins such as iron regulatory proteins, the hereditary hemochromatosis protein (HFE)–transferrin receptor complex, and hephaestin in regulating this transporter and in regulating iron transport across the intestinal epithelium are discussed. A speculative, but testable, model for the maintenance of iron homeostasis, which incorporates the changes in the iron-related proteins associated with the life cycle of the enterocyte as it journeys from the crypt to the tip of the villous is proposed.

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Molecular mechanisms of iron uptake in eukaryotes

Physiological Reviews ◽

10.1152/physrev.1996.76.1.31 ◽

1996 ◽

Vol 76 (1) ◽

pp. 31-47 ◽

Cited By ~ 130

Author(s):

D. M. de Silva ◽

C. C. Askwith ◽

J. Kaplan

Keyword(s):

Iron Uptake ◽

Mammalian Cells ◽

Iron Homeostasis ◽

Molecular Mechanisms ◽

Iron Acquisition ◽

Genetic Disorders ◽

Essential Element ◽

Recent Developments

Iron serves essential functions in both prokaryotes and eukaryotes, and cells have highly specialized mechanisms for acquiring and handling this metal. The primary mechanism by which the concentration of iron in biologic systems is controlled is through the regulation of iron uptake. Although the role of transferrin in mammalian iron homeostasis has been well characterized, the study of genetic disorders of iron metabolism has revealed other, transferrin-independent, mechanisms by which cells can acquire iron. In an attempt to understand how eukaryotic systems take up this essential element, investigators have begun studying the simple eukaryote Saccharomyces cerevisiae. Several genes have been identified and cloned that act in concert to allow iron acquisition from the environment. Some of these genes appear to have functional homologues in human systems. This review focuses on the recent developments in understanding eukaryotic iron uptake with an emphasis on the genetic and molecular characterization of these systems in both cultured mammalian cells and S. cerevisiae. An unexpected connection between iron and copper homeostasis has been revealed by recent genetic studies, which confirm biologic observations made several decades ago.

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IurV, Encoded by ORF VCA0231, Is Involved in the Regulation of Iron Uptake Genes in Vibrio cholerae

Genes ◽

10.3390/genes11101184 ◽

2020 ◽

Vol 11 (10) ◽

pp. 1184

Author(s):

Bernardo Sachman-Ruiz ◽

José Antonio Ibarra ◽

Paulina Estrada-de los Santos ◽

Alexia Torres Muñoz ◽

Begoña Giménez ◽

...

Keyword(s):

Vibrio Cholerae ◽

Iron Uptake ◽

Iron Homeostasis ◽

Iron Acquisition ◽

Pcr Analysis ◽

Quantitative Real Time Pcr ◽

Reading Frame ◽

Upregulated Genes ◽

In Silico Analyses ◽

Genomic Neighborhood

The pathogen Vibrio cholerae has multiple iron acquisition systems which allow bacteria to exploit a variety of iron sources across the different environments on which it thrives. The expression of such iron uptake systems is highly regulated, mainly by the master iron homeostasis regulator Fur but also by other mechanisms. Recently, we documented that the expression of many of the iron-responsive genes is also modulated by riboflavin. Among them, the open reading frame VCA0231, repressed both by riboflavin and iron, encodes a putative transcriptional regulator of the AraC/XylS family. Nonetheless, the genes or functions affected by this factor are unknown. In the present study, a series of in silico analyses was performed in order to identify the putative functions associated with the product of VCA0231. The STRING database predicted many iron uptake genes as functional partners for the product of VCA0231. In addition, a genomic neighborhood analysis with the Enzyme Function Initiative tools detected many Pfam families involved in iron homeostasis genetically associated with VCA0231. Moreover, a phylogenetic tree showed that other AraC/XylS members known to regulate siderophore utilization in bacteria clustered together and the product of VCA0231 localized in this cluster. This suggested that the product of VCA0231, here named IurV, is involved in the regulation of iron uptake processes. RNAseq was performed to determine the transcriptional effects of a deletion in VCA0231. A total of 52 genes were overexpressed and 21 genes were downregulated in response to the iurV deletion. Among these, several iron uptake genes and other iron homeostasis-related genes were found. Six gene ontology (GO) functional terms were enriched in the upregulated genes, of which five were related to iron metabolism. The regulatory pattern observed in the transcriptomics of a subset of genes was independently confirmed by quantitative real time PCR analysis. The results indicate that IurV is a novel regulator of the AraC/XylS family involved in the repression of iron uptake genes. Whether this effect is direct or indirect remains to be determined.

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Ontogenic changes in lactoferrin receptor and DMT1 in mouse small intestine: implications for iron absorption during early lifeThis paper is one of a selection of papers published in this Special Issue, entitled 7th International Conference on Lactoferrin: Structure, Function, and Applications, and has undergone the Journal's usual peer review process.

Biochemistry and Cell Biology ◽

10.1139/o06-059 ◽

2006 ◽

Vol 84 (3) ◽

pp. 337-344 ◽

Cited By ~ 32

Author(s):

Veronica Lopez ◽

Yasushi A. Suzuki ◽

Bo Lönnerdal

Keyword(s):

Small Intestine ◽

Early Life ◽

Iron Uptake ◽

Iron Transport ◽

Iron Homeostasis ◽

Apical Membrane ◽

Transport Pathway ◽

Divalent Metal Transporter 1 ◽

Uptake Pathway ◽

Lactoferrin Receptor

It has been proposed that lactoferrin receptor (LfR) may be involved in intestinal iron transport during early life. However, it is known that iron homeostasis is regulated by divalent metal transporter 1 (DMT1; Nramp2/DCT1) in the adult small intestine. To address the hypothesis that LfR may play a role as an alternative iron transport pathway during early life, we used immunohistochemistry (IHC) to examine the localization of mouse LfR (mLfR) and DMT1. In addition to studying the localization and abundance of LfR and DMT1 on the apical membrane, intestinal brush-border membrane vesicles (BBMV) were isolated during the first 3 postnatal weeks (postnatal day (PD) 0, 5, 10, and 20). We found that mLfR is expressed in fetal mice as early as gestational days (GD) 13.5, 15.5, and 18.5. A 34 kD band for mLfR was detected at PD 0 through PD 20 in total intestine homogenate. However, mLfR protein did not appear in the BBMV preparations until PD 5 and was highly expressed at PD 10. By IHC, DMT1 protein was minimally observed at PD 0 and PD 5, but by PD 10 DMT1 was predominantly localized in the apical membrane of the maturing intestine. BBMV fractionation revealed 50–120 kD protein bands for DMT1. In these BBMV preparations, the apical-membrane-associated 120 kD band for DMT1 increased in abundance with age. However, in the corresponding total homogenates, only the deglycosylated form of DMT1 (50 kD) was identified. These results indicate that DMT1 is mislocalized during late gestation, minimally expressed during early life, and predominantly expressed in its deglycosylated form until PD 20. The immunolocalization and abundant protein expression of mLfR suggest that accrual of iron from Lf may be the principal iron uptake pathway at this age. In conclusion, our findings support the notion that until the development-dependent expression of DMT1 in the intestine is induced, mLfR may serve as an alternative iron uptake pathway.

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

Microbiology ◽

10.1099/mic.0.27412-0 ◽

2005 ◽

Vol 151 (1) ◽

pp. 243-257 ◽

Cited By ~ 130

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.

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