scholarly journals A Novel Antimycobacterial Compound Acts as an Intracellular Iron Chelator

2015 ◽  
Vol 59 (4) ◽  
pp. 2256-2264 ◽  
Author(s):  
Marte S. Dragset ◽  
Giovanna Poce ◽  
Salvatore Alfonso ◽  
Teresita Padilla-Benavides ◽  
Thomas R. Ioerger ◽  
...  
Keyword(s):  
Iron Uptake ◽  
Iron Acquisition ◽  
Iron Chelator ◽  
Resistance Mutations ◽  
Intracellular Iron ◽  
Content Type ◽  
Type Vii Secretion ◽  
Cellular Target ◽  
Type Vii Secretion System ◽  
Mycobacterial Growth

ABSTRACTEfficient iron acquisition is crucial for the pathogenesis ofMycobacterium tuberculosis. Mycobacterial iron uptake and metabolism are therefore attractive targets for antitubercular drug development. Resistance mutations against a novel pyrazolopyrimidinone compound (PZP) that is active againstM. tuberculosishave been identified within the gene cluster encoding the ESX-3 type VII secretion system. ESX-3 is required for mycobacterial iron acquisition through the mycobactin siderophore pathway, which could indicate that PZP restricts mycobacterial growth by targeting ESX-3 and thus iron uptake. Surprisingly, we show that ESX-3 is not the cellular target of the compound. We demonstrate that PZP indeed targets iron metabolism; however, we found that instead of inhibiting uptake of iron, PZP acts as an iron chelator, and we present evidence that the compound restricts mycobacterial growth by chelating intrabacterial iron. Thus, we have unraveled the unexpected mechanism of a novel antimycobacterial compound.

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

mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
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.

scholarly journals Iron Acquisition in Mycobacterium avium subsp. paratuberculosis

2015 ◽  
Vol 198 (5) ◽  
pp. 857-866 ◽  
Author(s):  
Joyce Wang ◽  
Jalal Moolji ◽  
Alex Dufort ◽  
Alfredo Staffa ◽  
Pilar Domenech ◽  
...  
Keyword(s):  
Mycobacterium Avium ◽  
Iron Uptake ◽  
Genomic Island ◽  
Iron Acquisition ◽  
Laboratory Data ◽  
Uptake System ◽  
Intracellular Iron ◽  
Content Type ◽  
Iron Uptake System ◽  
Environmental Bacterium

ABSTRACTMycobacterium aviumsubsp.paratuberculosisis a host-adapted pathogen that evolved from the environmental bacteriumM. aviumsubsp.hominissuisthrough gene loss and gene acquisition. Growth ofM. aviumsubsp.paratuberculosisin the laboratory is enhanced by supplementation of the media with the iron-binding siderophore mycobactin J. Here we examined the production of mycobactins by related organisms and searched for an alternative iron uptake system inM. aviumsubsp.paratuberculosis. Through thin-layer chromatography and radiolabeled iron-uptake studies, we showed thatM. aviumsubsp.paratuberculosisis impaired for both mycobactin synthesis and iron acquisition. Consistent with these observations, we identified several mutations, including deletions, inM. aviumsubsp.paratuberculosisgenes coding for mycobactin synthesis. Using a transposon-mediated mutagenesis screen conditional on growth without myobactin, we identified a potential mycobactin-independent iron uptake system on aM. aviumsubsp.paratuberculosis-specific genomic island, LSPP15. We obtained a transposon (Tn) mutant with a disruption in the LSPP15 geneMAP3776cfor targeted study. The mutant manifests increased iron uptake as well as intracellular iron content, with genes downstream of the transposon insertion (MAP3775ctoMAP3772c[MAP3775-2c]) upregulated as the result of a polar effect. As an independent confirmation, we observed the same iron uptake phenotypes by overexpressingMAP3775-2cin wild-typeM. aviumsubsp.paratuberculosis. These data indicate that the horizontally acquired LSPP15 genes contribute to iron acquisition byM. aviumsubsp.paratuberculosis, potentially allowing the subsequent loss of siderophore production by this pathogen.IMPORTANCEMany microbes are able to scavenge iron from their surroundings by producing iron-chelating siderophores. One exception isMycobacterium aviumsubsp.paratuberculosis, a fastidious, slow-growing animal pathogen whose growth needs to be supported by exogenous mycobacterial siderophore (mycobactin) in the laboratory. Data presented here demonstrate that, compared to other closely relatedM. aviumsubspecies, mycobactin production and iron uptake are different inM. aviumsubsp.paratuberculosis, and these phenotypes may be caused by numerous deletions in its mycobactin biosynthesis pathway. Using a genomic approach, supplemented by targeted genetic and biochemical studies, we identified that LSPP15, a horizontally acquired genomic island, may encode an alternative iron uptake system. These findings shed light on the potential physiological consequence of horizontal gene transfer inM. aviumsubsp.paratuberculosisevolution.

scholarly journals Contribution of Active Iron Uptake toAcinetobacter baumanniiPathogenicity

2019 ◽  
Vol 87 (4) ◽  
Author(s):  
Federica Runci ◽  
Valentina Gentile ◽  
Emanuela Frangipani ◽  
Giordano Rampioni ◽  
Livia Leoni ◽  
...  
Keyword(s):  
Human Serum ◽  
Iron Uptake ◽  
Iron Acquisition ◽  
Human Infection ◽  
Intracellular Iron ◽  
Content Type ◽  
Promising Target ◽  
Essential Nutrient

ABSTRACTAcinetobacter baumanniiis an important nosocomial pathogen. Mechanisms that allowA. baumanniito cause human infection are still poorly understood. Iron is an essential nutrient for bacterial growthin vivo, and the multiplicity of iron uptake systems inA. baumanniisuggests that iron acquisition contributes to the ability ofA. baumanniito cause infection. In Gram-negative bacteria, active transport of ferrisiderophores and heme relies on the conserved TonB-ExbB-ExbD energy-transducing complex, while active uptake of ferrous iron is mediated by the Feo system. TheA. baumanniigenome invariably contains threetonBgenes (tonB1,tonB2, andtonB3), whose role in iron uptake is poorly understood. Here, we generatedA. baumanniimutants with knockout mutations in thefeoand/ortonBgene. We report thattonB3is essential forA. baumanniigrowth under iron-limiting conditions, whereastonB1,tonB2, andfeoBappear to be dispensable for ferric iron uptake.tonB3deletion resulted in reduced intracellular iron content despite siderophore overproduction, supporting a key role of TonB3 in iron uptake. In contrast to the case fortonB1andtonB2, the promoters oftonB3andfeocontain functional Fur boxes and are upregulated in iron-poor media. Both TonB3 and Feo systems are required for growth in complement-free human serum and contribute to resistance to the bactericidal activity of normal human serum, but only TonB3 appears to be essential for virulence in insect and mouse models of infection. Our findings highlight a central role of the TonB3 system forA. baumanniipathogenicity. Hence, TonB3 represents a promising target for novel antibacterial therapies and for the generation of attenuated vaccine strains.

scholarly journals Mycobacterial Esx-3 Requires Multiple Components for Iron Acquisition

mBio ◽  
2014 ◽  
Vol 5 (3) ◽  
Author(s):  
M. Sloan Siegrist ◽  
Magnus Steigedal ◽  
Rushdy Ahmad ◽  
Alka Mehra ◽  
Marte S. Dragset ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Iron Acquisition ◽  
Multiple Reaction Monitoring ◽  
Protein Export ◽  
Secretion Systems ◽  
Experimental Conditions ◽  
Content Type ◽  
Type Vii Secretion ◽  
Wide Range

ABSTRACT The type VII secretion systems are conserved across mycobacterial species and in many Gram-positive bacteria. While the well-characterized Esx-1 pathway is required for the virulence of pathogenic mycobacteria and conjugation in the model organism Mycobacterium smegmatis, Esx-3 contributes to mycobactin-mediated iron acquisition in these bacteria. Here we show that several Esx-3 components are individually required for function under low-iron conditions but that at least one, the membrane-bound protease MycP3 of M. smegmatis, is partially expendable. All of the esx-3 mutants tested, including the ΔmycP 3ms mutant, failed to export the native Esx-3 substrates EsxH ms and EsxG ms to quantifiable levels, as determined by targeted mass spectrometry. Although we were able to restore low-iron growth to the esx-3 mutants by genetic complementation, we found a wide range of complementation levels for protein export. Indeed, minute quantities of extracellular EsxH ms and EsxG ms were sufficient for iron acquisition under our experimental conditions. The apparent separation of Esx-3 function in iron acquisition from robust EsxG ms and EsxH ms secretion in the ΔmycP 3ms mutant and in some of the complemented esx-3 mutants compels reexamination of the structure-function relationships for type VII secretion systems. IMPORTANCE Mycobacteria have several paralogous type VII secretion systems, Esx-1 through Esx-5. Whereas Esx-1 is required for pathogenic mycobacteria to grow within an infected host, Esx-3 is essential for growth in vitro. We and others have shown that Esx-3 is required for siderophore-mediated iron acquisition. In this work, we identify individual Esx-3 components that contribute to this process. As in the Esx-1 system, most mutations that abolish Esx-3 protein export also disrupt its function. Unexpectedly, however, ultrasensitive quantitation of Esx-3 secretion by multiple-reaction-monitoring mass spectrometry (MRM-MS) revealed that very low levels of export were sufficient for iron acquisition under similar conditions. Although protein export clearly contributes to type VII function, the relationship is not absolute.

scholarly journals A Duplicated ESAT-6 Region of ESX-5 Is Involved in Protein Export and Virulence of Mycobacteria

2015 ◽  
Vol 83 (11) ◽  
pp. 4349-4361 ◽  
Author(s):  
Swati Shah ◽  
Joe R. Cannon ◽  
Catherine Fenselau ◽  
Volker Briken
Keyword(s):  
Secretion System ◽  
Bacterial Virulence ◽  
Inflammasome Activation ◽  
Zebrafish Model ◽  
Content Type ◽  
Type Vii Secretion ◽  
Specific Subset ◽  
Host Cell Death ◽  
Type Vii Secretion System

ABSTRACTThe ESX-5 secretion system ofMycobacterium tuberculosisis important for bacterial virulence and for the secretion of the large PE/PPE protein family, whose genes constitute 10% of theM. tuberculosisgenome. A four-gene region of the ESX-5 system is duplicated three times in theM. tuberculosisgenome, but the functions of these duplicates are unknown. Here we investigated one of these duplicates: the region carrying theesxI,esxJ,ppe15, andpe8genes (ESX-5a). An ESX-5a deletion mutant in the model systemM. marinumbackground was deficient in the secretion of some members of the PE/PPE family of proteins. Surprisingly, we also identified other proteins that are not members of this family, thus expanding the range of ESX-5 secretion substrates. In addition, we demonstrated that ESX-5a is important for the virulence ofM. marinumin the zebrafish model. Furthermore, we showed the role of theM. tuberculosisESX-5a region in inflammasome activation but not host cell death induction, which is different from the case for theM. tuberculosisESX-5 system. In conclusion, the ESX-5a region is nonredundant with its ESX-5 paralog and is necessary for secretion of a specific subset of proteins inM. tuberculosisandM. marinumthat are important for bacterial virulence ofM. marinum. Our findings point to a role for the three ESX-5 duplicate regions in the selection of substrates for secretion via ESX-5, and hence, they provide the basis for a refined model of the molecular mechanism of this type VII secretion system.

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

2013 ◽  
Vol 81 (11) ◽  
pp. 4182-4191 ◽  
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.

scholarly journals Deletion of the c2515 and c2516 Genes Affects Iron Uptake and Virulence of APEC O1 Strain E516

2021 ◽  
Vol 8 ◽  
Author(s):  
Qingqing Gao ◽  
Xi Li ◽  
Senyan Su ◽  
Lei Yang ◽  
Song Gao
Keyword(s):  
Iron Uptake ◽  
Target Genes ◽  
Iron Acquisition ◽  
Bacterial Colonization ◽  
Lethal Dose ◽  
Growth Defect ◽  
Cell Infection ◽  
Intracellular Iron

Avian pathogenic Escherichia coli (APEC), widely spread among poultry, is well-known to cause colibacillosis in chickens, which results in significant losses in poultry industry. The ability to uptake iron in the extra-intestinal environment is prerequisite for APEC survival. For adaptation to the low-iron environments, the bacteria have evolved multiple iron acquisition systems to ensure optimal iron uptake. However, many components of these iron acquisition pathways are still not clearly known. An in silico analysis of the genome of a septicemic APEC O1 strain E516 identified two putative iron transport genes homologous to the c2515 and c2516 genes from uropathogenic E. coli CFT073. In this study, we constructed the single and double gene deletion mutants, and studied their biological characteristic and pathogenic traits through in vitro and in vivo assays. Reverse transcriptase PCR (RT-PCR) analyses demonstrated that the mutations destroying the reading frame of the target genes abolished their transcription. Deletion of the single or double genes of c2515 and c2516 in APEC E516 weakened its ability to produce siderophore. Consistently, the mutants exhibited growth defect under iron-depleted conditions and the intracellular iron levels in the mutants were decreased in comparison with that of the wild-type (WT). Cell infection assays showed that the iron uptake defective mutants were more easily eliminated by the macrophage. Inactivation of the c2515 and c2516 genes affected bacterial colonization of chicken tissues, as well as the 50% lethal dose levels compared with the WT strain. Moreover, the expression levels of several iron uptake-related genes were significantly decreased in the double-deletion mutant. In total, the c2515 and c2516 may involve in siderophore-mediated iron uptake and participate in the pathogenesis of APEC O1 strain E516.

scholarly journals The Whole-Genome Sequence of Plasmid-Bearing Staphylococcus argenteus Strain B3-25B from Retail Beef Liver Encodes the Type VII Secretion System and Several Virulence Factors

2019 ◽  
Vol 8 (45) ◽  
Author(s):  
Leena Neyaz ◽  
Anand B. Karki ◽  
Mohamed K. Fakhr
Keyword(s):  
Virulence Factors ◽  
Genome Sequence ◽  
Secretion System ◽  
Whole Genome Sequence ◽  
Whole Genome ◽  
Circular Chromosome ◽  
Beef Liver ◽  
Content Type ◽  
Type Vii Secretion ◽  
Type Vii Secretion System

The whole-genome sequence of Staphylococcus argenteus strain B3-25B, isolated from retail beef liver, comprises a circular chromosome (2,676,222 bp) and a single plasmid (21,570 bp). The chromosome harbors genes encoding the type VII secretion system and several virulence factors.

scholarly journals Synthetic Porcine Hepcidin Exhibits Different Roles in Escherichia coli and Salmonella Infections

2017 ◽  
Vol 61 (10) ◽  
Author(s):  
Dan Liu ◽  
Zhen-Shun Gan ◽  
Wan Ma ◽  
Hai-Tao Xiong ◽  
Yun-Qing Li ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Bacterial Infections ◽  
Iron Status ◽  
Iron Chelator ◽  
Intracellular Iron ◽  
Content Type ◽  
Defense Strategies ◽  
Salmonella Infections

ABSTRACT Hepcidin, an antimicrobial peptide, was discovered to integrate diverse signals from iron status and an infection threat and orchestrate a series of host-protective responses. Several studies have investigated the antimicrobial role of hepcidin, but the results have been controversial. Here, we aimed to examine the role of hepcidin in bacterial adherence and invasion in vitro. We found that porcine hepcidin could decrease the amount of the extracellular pathogen enterotoxigenic Escherichia coli (ETEC) K88 that adhered to cells because it caused the aggregation of the bacteria. However, addition of hepcidin to macrophages infected with the intracellular pathogen Salmonella enterica serovar Typhimurium enhanced the intracellular growth of the pathogen through the degradation of ferroportin, an iron export protein, and then the sequestration of intracellular iron. Intracellular iron was unavailable by use of the iron chelator deferiprone (DFO), which reduced intracellular bacterial growth. These results demonstrate that hepcidin exhibits different functions in extracellular and intracellular bacterial infections, which suggests that different defense strategies should be taken to prevent bacterial infection.

scholarly journals Heme-iron plays a key role in the regulation of the Ess/Type VII secretion system ofStaphylococcus aureusRN6390

2017 ◽  
Author(s):  
M. Guillermina Casabona ◽  
Holger Kneuper ◽  
Daniela Alferes de Lima ◽  
Catriona P. Harkins ◽  
Martin Zoltner ◽  
...  
Keyword(s):  
Iron Homeostasis ◽  
Iron Acquisition ◽  
Secretion System ◽  
Heme Iron ◽  
Species Competition ◽  
Transcript Analysis ◽  
Type Vii Secretion ◽  
Protein Secretion System ◽  
Type Vii Secretion System ◽  
Translational Level

ABSTRACTTheStaphylococcus aureusType VII protein secretion system (T7SS) plays important roles in virulence and intra-species competition. Here we show that the T7SS in strain RN6390 is activated by supplementing the growth medium with hemoglobin, and its cofactor hemin (heme B). Transcript analysis and secretion assays suggest that activation by hemin occurs at a transcriptional and a post-translational level. Loss of T7 secretion activity by deletion ofessCresults in upregulation of genes required for iron acquisition. Taken together these findings suggest that the T7SS plays a role in iron homeostasis in at least someS. aureusstrains.

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