scholarly journals Characterization of the Achromobactin Iron Acquisition Operon in Sodalis glossinidius

2013 ◽  
Vol 79 (9) ◽  
pp. 2872-2881 ◽  
Author(s):  
Caitlin L. Smith ◽  
Brian L. Weiss ◽  
Serap Aksoy ◽  
Laura J. Runyen-Janecky

ABSTRACTSodalis glossinidiusis a facultative, extra- and intracellular symbiont found in most tissues of the tsetse fly (Glossiniasp.).Sodalishas a putative achromobactin siderophore iron acquisition system on the pSG1 plasmid. Reverse transcription (RT)-PCR analysis revealed that the achromobactin operon is transcribed as a single polycistronic molecule and is expressed whenSodalisis within the tsetse fly. Expression of the achromobactin operon was repressed under iron-replete conditions; in a mutant that lacks the iron-responsive transcriptional repressor protein Fur, expression was aberrantly derepressed under these iron-replete conditions, indicating that the Fur protein repressed achromobactin gene expression when iron was plentiful. A putative Fur binding site within theSodalisachromobactin promoter bound Fur inEscherichia coliFur titration assays. Wild-typeSodalisproduced detectable siderophorein vitro, but a mutation in the putative achromobactin biosynthesis geneacsDeliminated detectable siderophore production inSodalis. Reduced growth of the siderophore synthesis mutant was reconstituted by addition of exogenous achromobactin, suggesting the strain retains a functional siderophore transport system; however, reduced growth of aSodalisferric-siderophore outer membrane receptor mutant with a mutation inacrwas not reconstituted by exogenous siderophore due to its defective transporter. TheSodalissiderophore synthesis mutant showed reduced growth in tsetse that lacked endogenous symbionts (aposymbiotic) when the flies were inoculated withSodalisintrathoracically, but not when inoculatedper os. Our findings suggest thatSodalissiderophores play a role in iron acquisition in certain tsetse fly tissues and provide evidence for the regulation of iron acquisition mechanisms in insect symbionts.

2015 ◽  
Vol 81 (8) ◽  
pp. 2900-2909 ◽  
Author(s):  
Gili Hrusa ◽  
William Farmer ◽  
Brian L. Weiss ◽  
Taylor Applebaum ◽  
Jose Santinni Roma ◽  
...  

ABSTRACTSodalis glossinidiusis an intra- and extracellular symbiont of the tsetse fly (Glossinasp.), which feeds exclusively on vertebrate blood.S. glossinidiusresides in a wide variety of tsetse tissues and may encounter environments that differ dramatically in iron content. TheSodalischromosome encodes a putative TonB-dependent outer membrane heme transporter (HemR) and a putative periplasmic/inner membrane ABC heme permease system (HemTUV). Because these gene products mediate iron acquisition processes by other enteric bacteria, we characterized their regulation and physiological role in theSodalis/tsetse system. Our results show that thehemRandtonBgenes are expressed byS. glossinidiusin the tsetse fly. Furthermore, transcription ofhemRinSodalisis repressed in a high-iron environment by the iron-responsive transcriptional regulator Fur. Expression of theS. glossinidiushemRandhemTUVgenes in anEscherichia colistrain unable to use heme as an iron source stimulated growth in the presence of heme or hemoglobin as the sole iron source. This stimulation was dependent on the presence of either theE. coliorSodalistonBgene.SodalistonBandhemRmutant strains were defective in their ability to colonize the gut of tsetse flies that lacked endogenous symbionts, while wild-typeS. glossinidiusproliferated in this same environment. Finally, we show that theSodalisHemR protein is localized to the bacterial membrane and appears to bind hemin. Collectively, this study provides strong evidence that TonB-dependent, HemR-mediated iron acquisition is important for the maintenance of symbiont homeostasis in the tsetse fly, and it provides evidence for the expression of bacterial high-affinity iron acquisition genes in insect symbionts.


2012 ◽  
Vol 78 (21) ◽  
pp. 7760-7768 ◽  
Author(s):  
Michele A. Maltz ◽  
Brian L. Weiss ◽  
Michelle O'Neill ◽  
Yineng Wu ◽  
Serap Aksoy

ABSTRACTMany bacteria successfully colonize animals by forming protective biofilms. Molecular processes that underlie the formation and function of biofilms in pathogenic bacteria are well characterized. In contrast, the relationship between biofilms and host colonization by symbiotic bacteria is less well understood. Tsetse flies (Glossinaspp.) house 3 maternally transmitted symbionts, one of which is a commensal (Sodalis glossinidius) found in several host tissues, including the gut. We determined thatSodalisforms biofilms in the tsetse gut and that this process is influenced by theSodalisouter membrane protein A (OmpA). MutantSodalisstrains that do not produce OmpA (SodalisΔOmpA mutants) fail to form biofilmsin vitroand are unable to colonize the tsetse gut unless endogenous symbiotic bacteria are present. Our data indicate that in the absence of biofilms,SodalisΔOmpA mutant cells are exposed to and eliminated by tsetse's innate immune system, suggesting that biofilms helpSodalisevade the host immune system. Tsetse is the sole vector of pathogenic African trypanosomes, which also reside in the fly gut. Acquiring a better understanding of the dynamics that promoteSodaliscolonization of the tsetse gut may enhance the development of novel disease control strategies.


mBio ◽  
2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Rasmus Lykke Marvig ◽  
Søren Damkiær ◽  
S. M. Hossein Khademi ◽  
Trine M. Markussen ◽  
Søren Molin ◽  
...  

ABSTRACTPseudomonas aeruginosaairway infections are a major cause of mortality and morbidity of cystic fibrosis (CF) patients. In order to persist,P. aeruginosadepends on acquiring iron from its host, and multiple different iron acquisition systems may be active during infection. This includes the pyoverdine siderophore and thePseudomonasheme utilization (phu) system. While the regulation and mechanisms of several iron-scavenging systems are well described, it is not clear whether such systems are targets for selection during adaptation ofP. aeruginosato the host environment. Here we investigated the within-host evolution of the transmissibleP. aeruginosaDK2 lineage. We found positive selection for promoter mutations leading to increased expression of thephusystem. By mimicking conditions of the CF airwaysin vitro, we experimentally demonstrate that increased expression ofphuRconfers a growth advantage in the presence of hemoglobin, thus suggesting thatP. aeruginosaevolves toward iron acquisition from hemoglobin. To rule out that this adaptive trait is specific to the DK2 lineage, we inspected the genomes of additionalP. aeruginosalineages isolated from CF airways and found similar adaptive evolution in two distinct lineages (DK1 and PA clone C). Furthermore, in all three lineages,phuRpromoter mutations coincided with the loss of pyoverdine production, suggesting that within-host adaptation toward heme utilization is triggered by the loss of pyoverdine production. Targeting heme utilization might therefore be a promising strategy for the treatment ofP. aeruginosainfections in CF patients.IMPORTANCEMost bacterial pathogens depend on scavenging iron within their hosts, which makes the battle for iron between pathogens and hosts a hallmark of infection. Accordingly, the ability of the opportunistic pathogenPseudomonas aeruginosato cause chronic infections in cystic fibrosis (CF) patients also depends on iron-scavenging systems. While the regulation and mechanisms of several such iron-scavenging systems have been well described, not much is known about how the within-host selection pressures act on the pathogens’ ability to acquire iron. Here, we investigated the within-host evolution ofP. aeruginosa, and we found evidence thatP. aeruginosaduring long-term infections evolves toward iron acquisition from hemoglobin. This adaptive strategy might be due to a selective loss of other iron-scavenging mechanisms and/or an increase in the availability of hemoglobin at the site of infection. This information is relevant to the design of novel CF therapeutics and the development of models of chronic CF infections.


2014 ◽  
Vol 80 (19) ◽  
pp. 6212-6222 ◽  
Author(s):  
Jun Min ◽  
Jun-Jie Zhang ◽  
Ning-Yi Zhou

ABSTRACTBurkholderiasp. strain SJ98 (DSM 23195) utilizes 2-chloro-4-nitrophenol (2C4NP) orpara-nitrophenol (PNP) as a sole source of carbon and energy. Here, by genetic and biochemical analyses, a 2C4NP catabolic pathway different from those of all other 2C4NP utilizers was identified with chloro-1,4-benzoquinone (CBQ) as an intermediate. Reverse transcription-PCR analysis showed that all of thepnpgenes in thepnpABA1CDEFcluster were located in a single operon, which is significantly different from the genetic organization of all other previously reported PNP degradation gene clusters, in which the structural genes were located in three different operons. All of the Pnp proteins were purified to homogeneity as His-tagged proteins. PnpA, a PNP 4-monooxygenase, was found to be able to catalyze the monooxygenation of 2C4NP to CBQ. PnpB, a 1,4-benzoquinone reductase, has the ability to catalyze the reduction of CBQ to chlorohydroquinone. Moreover, PnpB is also able to enhance PnpA activityin vitroin the conversion of 2C4NP to CBQ. Genetic analyses indicated thatpnpAplays an essential role in the degradation of both 2C4NP and PNP by gene knockout and complementation. In addition to being responsible for the lower pathway of PNP catabolism, PnpCD, PnpE, and PnpF were also found to be likely involved in that of 2C4NP catabolism. These results indicated that the catabolism of 2C4NP and that of PNP share the same gene cluster in strain SJ98. These findings fill a gap in our understanding of the microbial degradation of 2C4NP at the molecular and biochemical levels.


mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Rebecca J. Hall ◽  
Lindsey A. Flanagan ◽  
Michael J. Bottery ◽  
Vicki Springthorpe ◽  
Stephen Thorpe ◽  
...  

ABSTRACTThe tsetse fly is the insect vector for theTrypanosoma bruceiparasite, the causative agent of human African trypanosomiasis. The colonization and spread of the trypanosome correlate positively with the presence of a secondary symbiotic bacterium,Sodalis glossinidius. The metabolic requirements and interactions of the bacterium with its host are poorly understood, and herein we describe a metabolic model ofS. glossinidiusmetabolism. The model enabled the design and experimental verification of a defined medium that supportsS. glossinidiusgrowthex vivo. This has been used subsequently to analyzein vitroaspects ofS. glossinidiusmetabolism, revealing multiple unique adaptations of the symbiont to its environment. Continued dependence on a sugar, and the importance of the chitin monomerN-acetyl-d-glucosamine as a carbon and energy source, suggests adaptation to host-derived molecules. Adaptation to the amino acid-rich blood diet is revealed by a strong dependence onl-glutamate as a source of carbon and nitrogen and by the ability to rescue a predictedl-arginine auxotrophy. Finally, the selective loss of thiamine biosynthesis, a vitamin provided to the host by the primary symbiontWigglesworthia glossinidia, reveals an intersymbiont dependence. The reductive evolution ofS. glossinidiusto exploit environmentally derived metabolites has resulted in multiple weaknesses in the metabolic network. These weaknesses may become targets for reagents that inhibitS. glossinidiusgrowth and aid the reduction of trypanosomal transmission.IMPORTANCEHuman African trypanosomiasis is caused by theTrypanosoma bruceiparasite. The tsetse fly vector is of interest for its potential to prevent disease spread, as it is essential forT. bruceilife cycle progression and transmission. The tsetse’s mutualistic endosymbiontSodalis glossinidiushas a link to trypanosome establishment, providing a disease control target. Here, we describe a new, experimentally verified model ofS. glossinidiusmetabolism. This model has enabled the development of a defined growth medium that was used successfully to test aspects ofS. glossinidiusmetabolism. We presentS. glossinidiusas uniquely adapted to life in the tsetse, through its reliance on the blood diet and host-derived sugars. Additionally,S. glossinidiushas adapted to the tsetse’s obligate symbiontWigglesworthia glossinidiaby scavenging a vitamin it produces for the insect. This work highlights the use of metabolic modeling to design defined growth media for symbiotic bacteria and may provide novel inhibitory targets to block trypanosome transmission.


mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Stefanie Dichtl ◽  
Egon Demetz ◽  
David Haschka ◽  
Piotr Tymoszuk ◽  
Verena Petzer ◽  
...  

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.


2012 ◽  
Vol 79 (5) ◽  
pp. 1573-1579 ◽  
Author(s):  
Yan Chen ◽  
Hsiang-yun Chi ◽  
Dauenpen Meesapyodsuk ◽  
Xiao Qiu

ABSTRACTThe effective flux between phospholipids and neutral lipids is critical for a high level of biosynthesis and accumulation of very-long-chain polyunsaturated fatty acids (VLCPUFAs), such as arachidonic acid (ARA; 20:4n-6), eicosapentaenoic acid (EPA; 20:5n-3), and docosahexaenoic acid (DHA; 22:6n-3). Here we describe a cDNA (PiCPT1) fromPhytophthora infestans, a VLCPUFA-producing oomycete, that may have a role in acyl trafficking between diacylglycerol (DAG) and phosphatidylcholine (PC) during the biosynthesis of VLCPUFAs. The cDNA encodes a polypeptide of 393 amino acids with a conserved CDP-alcohol phosphotransferase motif and approximately 27% amino acid identity to theSaccharomyces cerevisiaecholinephosphotransferase (ScCPT1).In vitroassays indicate that PiCPT1 has high cholinephosphotransferase (CPT) activity but no ethanolaminephosphotransferase (EPT) activity. Substrate specificity assays show that it prefers VLCPUFA-containing DAGs, such as ARA DAG and DHA DAG, as substrates. Real-time PCR analysis reveals that expression ofPiCPT1was upregulated inP. infestansorganisms fed with exogenous VLCPUFAs. These results lead us to conclude that PiCPT1 is a VLCPUFA-specific CPT which may play an important role in shuffling VLCPUFAs from DAG to PC in the biosynthesis of VLCPUFAs inP. infestans.


2015 ◽  
Vol 197 (11) ◽  
pp. 1873-1885 ◽  
Author(s):  
Aleksandr Sverzhinsky ◽  
Jacqueline W. Chung ◽  
Justin C. Deme ◽  
Lucien Fabre ◽  
Kristian T. Levey ◽  
...  

ABSTRACTIron acquisition at the outer membrane (OM) of Gram-negative bacteria is powered by the proton motive force (PMF) of the cytoplasmic membrane (CM), harnessed by the CM-embedded complex of ExbB, ExbD, and TonB. Its stoichiometry, ensemble structural features, and mechanism of action are unknown. By panning combinatorial phage libraries, periplasmic regions of dimerization between ExbD and TonB were predicted. Using overexpression of full-length His6-taggedexbB-exbDand S-taggedtonB, we purified detergent-solubilized complexes of ExbB-ExbD-TonB fromEscherichia coli. Protein-detergent complexes of ∼230 kDa with a hydrodynamic radius of ∼6.0 nm were similar to previously purified ExbB4-ExbD2complexes. Significantly, they differed in electronegativity by native agarose gel electrophoresis. The stoichiometry was determined to be ExbB4-ExbD1-TonB1. Single-particle electron microscopy agrees with this stoichiometry. Two-dimensional averaging supported the phage display predictions, showing two forms of ExbD-TonB periplasmic heterodimerization: extensive and distal. Three-dimensional (3D) particle classification showed three representative conformations of ExbB4-ExbD1-TonB1. Based on our structural data, we propose a model in which ExbD shuttles a proton across the CM via an ExbB interprotein rearrangement. Proton translocation would be coupled to ExbD-mediated collapse of extended TonB in complex with ligand-loaded receptors in the OM, followed by repositioning of TonB through extensive dimerization with ExbD. Here we present the first report for purification of the ExbB-ExbD-TonB complex, molar ratios within the complex (4:1:1), and structural biology that provides insights into 3D organization.IMPORTANCEReceptors in the OM of Gram-negative bacteria allow entry of iron-bound siderophores that are necessary for pathogenicity. Numerous iron-acquisition strategies rely upon a ubiquitous and unique protein for energization: TonB. Complexed with ExbB and ExbD, the Ton system links the PMF to OM transport. Blocking iron uptake by targeting a vital nanomachine holds promise in therapeutics. Despite much research, the stoichiometry, structural arrangement, and molecular mechanism of the CM-embedded ExbB-ExbD-TonB complex remain unreported. Here we demonstratein vitroevidence of ExbB4-ExbD1-TonB1complexes. Using 3D EM, we reconstructed the complex in three conformational states that show variable ExbD-TonB heterodimerization. Our structural observations form the basis of a model for TonB-mediated iron acquisition.


mBio ◽  
2014 ◽  
Vol 5 (3) ◽  
Author(s):  
M. Sloan Siegrist ◽  
Magnus Steigedal ◽  
Rushdy Ahmad ◽  
Alka Mehra ◽  
Marte S. Dragset ◽  
...  

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.


2013 ◽  
Vol 57 (10) ◽  
pp. 5138-5140 ◽  
Author(s):  
Shichun Lun ◽  
Haidan Guo ◽  
John Adamson ◽  
Justin S. Cisar ◽  
Tony D. Davis ◽  
...  

ABSTRACTMycobactin biosynthesis inMycobacterium tuberculosisfacilitates iron acquisition, which is required for growth and virulence. The mycobactin biosynthesis inhibitor salicyl-AMS [5′-O-(N-salicylsulfamoyl)adenosine] inhibitsM. tuberculosisgrowthin vitrounder iron-limited conditions. Here, we conducted a single-dose pharmacokinetic study and a monotherapy study of salicyl-AMS with mice. Intraperitoneal injection yielded much better pharmacokinetic parameter values than oral administration did. Monotherapy of salicyl-AMS at 5.6 or 16.7 mg/kg significantly inhibitedM. tuberculosisgrowth in the mouse lung, providing the firstin vivoproof of concept for this novel antibacterial strategy.


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