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Miller AH, Marks F, Chan L, Botella H, Schnappinger D, Ehrt S. Interruption of mycothiol synthesis and intracellular redox status impact iron-regulated reporter activation in Mycobacterium smegmatis. Microbiol Spectr 2024; 12:e0048724. [PMID: 38860795 PMCID: PMC11218476 DOI: 10.1128/spectrum.00487-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 05/04/2024] [Indexed: 06/12/2024] Open
Abstract
Iron scavenging is required for full virulence of mycobacterial pathogens. During infection, the host immune response restricts mycobacterial access to iron, which is essential for bacterial respiration and DNA synthesis. The Mycobacterium tuberculosis iron-dependent regulator (IdeR) responds to changes in iron accessibility by repressing iron-uptake genes when iron is available. In contrast, iron-uptake gene transcription is induced when iron is depleted. The ideR gene is essential in M. tuberculosis and is required for bacterial growth. To further study how iron regulates transcription, wee developed an iron responsive reporter system that relies on an IdeR-regulated promoter to drive Cre and loxP mediated recombination in Mycobacterium smegmatis. Recombination leads to the expression of an antibiotic resistance gene so that mutations that activate the IdeR-regulated promoter can be selected. A transposon library in the background of this reporter system was exposed to media containing iron and hemin, and this resulted in the selection of mutants in the antioxidant mycothiol synthesis pathway. We validated that inactivation of the mycothiol synthesis gene mshA results in increased recombination and increased IdeR-regulated promoter activity in the reporter system. Further, we show that vitamin C, which has been shown to oxidize iron through the Fenton reaction, can decrease promoter activity in the mshA mutant. We conclude that the intracellular redox state balanced by mycothiol can alter IdeR activity in the presence of iron.IMPORTANCEMycobacterium smegmatis is a tractable organism to study mycobacterial gene regulation. We used M. smegmatis to construct a novel recombination-based reporter system that allows for the selection of mutations that deregulate a promoter of interest. Transposon mutagenesis and insertion sequencing (TnSeq) in the recombination reporter strain identified genes that impact iron regulated promoter activity in mycobacteria. We found that the mycothiol synthesis gene mshA is required for IdeR mediated transcriptional regulation by maintaining intracellular redox balance. By affecting the oxidative state of the intracellular environment, mycothiol can modulate iron-dependent transcriptional activity. Taken more broadly, this novel reporter system can be used in combination with transposon mutagenesis to identify genes that are required by Mycobacterium tuberculosis to overcome temporary or local changes in iron availability during infection.
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Affiliation(s)
- Alexandra H Miller
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA
- Immunology and Microbial Pathogenesis Graduate Program, Weill Cornell Graduate School of Medical Sciences, Cornell University, New York, New York, USA
| | - Frances Marks
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA
- Biochemistry and Structural Biology, Cell and Developmental Biology, and Molecular Biology Program, Weill Cornell Graduate School of Medical Sciences, Cornell University, New York, New York, USA
| | - Luming Chan
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA
| | - Helene Botella
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA
| | - Dirk Schnappinger
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA
| | - Sabine Ehrt
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA
- Immunology and Microbial Pathogenesis Graduate Program, Weill Cornell Graduate School of Medical Sciences, Cornell University, New York, New York, USA
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2
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Shankar G, Akhter Y. Stealing survival: Iron acquisition strategies of Mycobacteriumtuberculosis. Biochimie 2024:S0300-9084(24)00142-1. [PMID: 38901792 DOI: 10.1016/j.biochi.2024.06.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2024] [Revised: 06/07/2024] [Accepted: 06/18/2024] [Indexed: 06/22/2024]
Abstract
Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), faces iron scarcity within the host due to immune defenses. This review explores the importance of iron for Mtb and its strategies to overcome iron restriction. We discuss how the host limits iron as an innate immune response and how Mtb utilizes various iron acquisition systems, particularly the siderophore-mediated pathway. The review illustrates the structure and biosynthesis of mycobactin, a key siderophore in Mtb, and the regulation of its production. We explore the potential of targeting siderophore biosynthesis and uptake as a novel therapeutic approach for TB. Finally, we summarize current knowledge on Mtb's iron acquisition and highlight promising directions for future research to exploit this pathway for developing new TB interventions.
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Affiliation(s)
- Gauri Shankar
- Department of Biotechnology, Babasaheb Bhimrao Ambedkar University, Vidya Vihar, Raebareli Road, Lucknow, Uttar Pradesh, 226 025, India
| | - Yusuf Akhter
- Department of Biotechnology, Babasaheb Bhimrao Ambedkar University, Vidya Vihar, Raebareli Road, Lucknow, Uttar Pradesh, 226 025, India.
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3
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Williams JT, Baker JJ, Zheng H, Dechow SJ, Fallon J, Murto M, Albrecht VJ, Gilliland HN, Olive AJ, Abramovitch RB. A genetic selection for Mycobacterium smegmatis mutants tolerant to killing by sodium citrate defines a combined role for cation homeostasis and osmotic stress in cell death. mSphere 2023; 8:e0035823. [PMID: 37681985 PMCID: PMC10597346 DOI: 10.1128/msphere.00358-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 07/23/2023] [Indexed: 09/09/2023] Open
Abstract
Mycobacteria can colonize environments where the availability of metal ions is limited. Biological or inorganic chelators play an important role in limiting metal availability, and we developed a model to examine Mycobacterium smegmatis survival in the presence of the chelator sodium citrate. We observed that instead of restricting M. smegmatis growth, concentrated sodium citrate killed M. smegmatis. RNAseq analysis during sodium citrate treatment revealed transcriptional signatures of metal starvation and hyperosmotic stress. Notably, metal starvation and hyperosmotic stress, individually, do not kill M. smegmatis under these conditions. A forward genetic transposon selection was conducted to examine why sodium citrate was lethal, and several sodium-citrate-tolerant mutants were isolated. Based on the identity of three tolerant mutants, mgtE, treZ, and fadD6, we propose a dual stress model of killing by sodium citrate, where sodium citrate chelate metals from the cell envelope and then osmotic stress in combination with a weakened cell envelope causes cell lysis. This sodium citrate tolerance screen identified mutants in several other genes with no known function, with most conserved in the pathogen M. tuberculosis. Therefore, this model will serve as a basis to define their functions, potentially in maintaining cell wall integrity, cation homeostasis, or osmotolerance. IMPORTANCE Bacteria require mechanisms to adapt to environments with differing metal availability. When Mycobacterium smegmatis is treated with high concentrations of the metal chelator sodium citrate, the bacteria are killed. To define the mechanisms underlying killing by sodium citrate, we conducted a genetic selection and observed tolerance to killing in mutants of the mgtE magnesium transporter. Further characterization studies support a model where killing by sodium citrate is driven by a weakened cell wall and osmotic stress, that in combination cause cell lysis.
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Affiliation(s)
- John T. Williams
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Jacob J. Baker
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Huiqing Zheng
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Shelby J. Dechow
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Jared Fallon
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Megan Murto
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Veronica J. Albrecht
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Haleigh N. Gilliland
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Andrew J. Olive
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Robert B. Abramovitch
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
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4
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Kumar G, Adhikrao PA. Targeting Mycobacterium tuberculosis iron-scavenging tools: a recent update on siderophores inhibitors. RSC Med Chem 2023; 14:1885-1913. [PMID: 37859726 PMCID: PMC10583813 DOI: 10.1039/d3md00201b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 08/22/2023] [Indexed: 10/21/2023] Open
Abstract
Among the various bacterial infections, tuberculosis (TB) remains a life-threatening infectious disease responsible as the most significant cause of mortality and morbidity worldwide. The co-infection of human immunodeficiency virus (HIV) in association with TB burdens the healthcare system substantially. Notably, M.tb possesses defence against most antitubercular antibiotic drugs, and the efficacy of existing frontline anti-TB drugs is waning. Also, new and recurring cases of TB from resistant bacteria such as multidrug-resistant TB (MDR), extensively drug-resistant TB (XDR), and totally drug-resistant TB (TDR) strains are increasing. Hence, TB begs the scientific community to explore the new therapeutic class of compounds with their novel mechanism. M.tb requires iron from host cells to sustain, grow, and carry out several biological processes. M.tb has developed strategic methods of acquiring iron from the surrounding environment. In this communication, we discuss an overview of M.tb iron-scavenging tools. Also, we have summarized recently identified MbtA and MbtI inhibitors, which prevent M.tb from scavenging iron. These iron-scavenging tool inhibitors have the potential to be developed as anti-TB agents/drugs.
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Affiliation(s)
- Gautam Kumar
- Department of Natural Products, Chemical Sciences, National Institute of Pharmaceutical Education and Research-Hyderabad (NIPER-Hyderabad) Balanagar Hyderabad 500037 India
| | - Patil Amruta Adhikrao
- Department of Natural Products, Chemical Sciences, National Institute of Pharmaceutical Education and Research-Hyderabad (NIPER-Hyderabad) Balanagar Hyderabad 500037 India
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5
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Elucidation of the coping strategy in an OMP homozygous knockout mutant of Synechocystis 6803 defective in iron uptake. Arch Microbiol 2022; 204:358. [DOI: 10.1007/s00203-022-02968-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 04/18/2022] [Accepted: 05/09/2022] [Indexed: 11/02/2022]
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6
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Control of subunit stoichiometry in single-chain MspA nanopores. Biophys J 2022; 121:742-754. [PMID: 35101416 PMCID: PMC8943699 DOI: 10.1016/j.bpj.2022.01.022] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Revised: 12/18/2021] [Accepted: 01/25/2022] [Indexed: 11/21/2022] Open
Abstract
Transmembrane protein channels enable fast and highly sensitive detection of single molecules. Nanopore sequencing of DNA was achieved using an engineered Mycobacterium smegmatis porin A (MspA) in combination with a motor enzyme. Due to its favorable channel geometry, the octameric MspA pore exhibits the highest current level compared with other pore proteins. To date, MspA is the only protein nanopore with a published record of DNA sequencing. While widely used in commercial devices, nanopore sequencing of DNA suffers from significant base-calling errors due to stochastic events of the complex DNA-motor-pore combination and the contribution of up to five nucleotides to the signal at each position. Different mutations in specific subunits of a pore protein offer an enormous potential to improve nucleotide resolution and sequencing accuracy. However, individual subunits of MspA and other oligomeric protein pores are randomly assembled in vivo and in vitro, preventing the efficient production of designed pores with different subunit mutations. In this study, we converted octameric MspA into a single-chain pore by connecting eight subunits using peptide linkers. Lipid bilayer experiments demonstrated that single-chain MspA formed membrane-spanning channels and discriminated all four nucleotides identical to MspA produced from monomers in DNA hairpin experiments. Single-chain constructs comprising three, five, six, and seven connected subunits assembled to functional channels, demonstrating a remarkable plasticity of MspA to different subunit stoichiometries. Thus, single-chain MspA constitutes a new milestone in the optimization of MspA as a biosensor for DNA sequencing and many other applications by enabling the production of pores with distinct subunit mutations and pore diameters.
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7
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Shyam M, Verma H, Bhattacharje G, Mukherjee P, Singh S, Kamilya S, Jalani P, Das S, Dasgupta A, Mondal A, Das AK, Singh A, Brucoli F, Bagnéris C, Dickman R, Basavanakatti VN, Naresh Babu P, Sankaran V, Dev A, Sinha BN, Bhakta S, Jayaprakash V. Mycobactin Analogues with Excellent Pharmacokinetic Profile Demonstrate Potent Antitubercular Specific Activity and Exceptional Efflux Pump Inhibition. J Med Chem 2022; 65:234-256. [PMID: 34981940 DOI: 10.1021/acs.jmedchem.1c01349] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study, we have designed and synthesized pyrazoline analogues that partially mimic the structure of mycobactin, to address the requirement of novel therapeutics to tackle the emerging global challenge of antimicrobial resistance (AMR). Our investigation resulted in the identification of novel lead compounds 44 and 49 as potential mycobactin biosynthesis inhibitors against mycobacteria. Moreover, candidates efficiently eradicated intracellularly surviving mycobacteria. Thermofluorimetric analysis and molecular dynamics simulations suggested that compounds 44 and 49 bind to salicyl-AMP ligase (MbtA), a key enzyme in the mycobactin biosynthetic pathway. To the best of our knowledge, these are the first rationally designed mycobactin inhibitors to demonstrate an excellent in vivo pharmacokinetic profile. In addition, these compounds also exhibited more potent whole-cell efflux pump inhibition than known efflux pump inhibitors verapamil and chlorpromazine. Results from this study pave the way for the development of 3-(2-hydroxyphenyl)-5-(aryl)-pyrazolines as a new weapon against superbug-associated AMR challenges.
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Affiliation(s)
- Mousumi Shyam
- Department of Pharmaceutical Sciences & Technology, Birla Institute of Technology, Mesra, Ranchi 835215, Jharkhand, India.,Mycobacteria Research Laboratory, Department of Biological Sciences, Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet Street, London WC1E 7HX, U.K
| | - Harshita Verma
- Mycobacteria Research Laboratory, Department of Biological Sciences, Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet Street, London WC1E 7HX, U.K
| | - Gourab Bhattacharje
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | | | | | - Sujit Kamilya
- Solid State and Structural Chemistry Unit, Indian Institute of Science, CV Raman Avenue, Bangalore 560012, India
| | - Pushpendu Jalani
- Microbiology Division, CSIR-Central Drug Research Institute, Sector 10 Janakipuram Extension, Sitapur Road, Lucknow 226031, India
| | - Swetarka Das
- Microbiology Division, CSIR-Central Drug Research Institute, Sector 10 Janakipuram Extension, Sitapur Road, Lucknow 226031, India
| | - Arunava Dasgupta
- Microbiology Division, CSIR-Central Drug Research Institute, Sector 10 Janakipuram Extension, Sitapur Road, Lucknow 226031, India
| | - Abhishake Mondal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, CV Raman Avenue, Bangalore 560012, India
| | - Amit Kumar Das
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | | | - Federico Brucoli
- Leicester School of Pharmacy, De Montfort University, The Gateway, Leicester LE1 9BH, U.K
| | - Claire Bagnéris
- Mycobacteria Research Laboratory, Department of Biological Sciences, Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet Street, London WC1E 7HX, U.K
| | - Rachael Dickman
- Pharmaceutical and Biological Chemistry, UCL School of Pharmacy, University of London, London WC1N 1AX, U.K
| | | | | | - Vadivelan Sankaran
- Eurofins Advinus Limited, 21 & 22, Peenya Industrial area, Bengaluru 560058, India
| | - Abhimanyu Dev
- Department of Pharmaceutical Sciences & Technology, Birla Institute of Technology, Mesra, Ranchi 835215, Jharkhand, India
| | - Barij Nayan Sinha
- Department of Pharmaceutical Sciences & Technology, Birla Institute of Technology, Mesra, Ranchi 835215, Jharkhand, India
| | - Sanjib Bhakta
- Mycobacteria Research Laboratory, Department of Biological Sciences, Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet Street, London WC1E 7HX, U.K
| | - Venkatesan Jayaprakash
- Department of Pharmaceutical Sciences & Technology, Birla Institute of Technology, Mesra, Ranchi 835215, Jharkhand, India
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8
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Lewin A, Kamal E, Semmler T, Winter K, Kaiser S, Schäfer H, Mao L, Eschenhagen P, Grehn C, Bender J, Schwarz C. Genetic diversification of persistent Mycobacterium abscessus within cystic fibrosis patients. Virulence 2021; 12:2415-2429. [PMID: 34546836 PMCID: PMC8526041 DOI: 10.1080/21505594.2021.1959808] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Mycobacterium (M.) abscessus infections in Cystic Fibrosis (CF) patients cause a deterioration of lung function. Treatment of these multidrug-resistant pathogens is associated with severe side-effects, while frequently unsuccessful. Insight on M. abscessus genomic evolvement during chronic lung infection would be beneficial for improving treatment strategies. A longitudinal study enrolling 42 CF patients was performed at a CF center in Berlin, Germany, to elaborate phylogeny and genomic diversification of in-patient M. abscessus. Eleven of the 42 CF patients were infected with M. abscessus. Five of these 11 patients were infected with global human-transmissible M. abscessus cluster strains. Phylogenetic analysis of 88 genomes from isolates of the 11 patients excluded occurrence of M. abscessus transmission among members of the study group. Genome sequencing and variant analysis of 30 isolates from 11 serial respiratory samples collected over 4.5 years from a chronically infected patient demonstrated accumulation of gene mutations. In total, 53 genes exhibiting non-synonymous variations were identified. Enrichment analysis emphasized genes involved in synthesis of glycopeptidolipids, genes from the embABC (arabinosyltransferase) operon, betA (glucose-methanol-choline oxidoreductase) and choD (cholesterol oxidase). Genetic diversity evolved in a variety of virulence- and resistance-associated genes. The strategy of M. abscessus populations in chronic lung infection is not clonal expansion of dominant variants, but to sustain simultaneously a wide range of genetic variants facilitating adaptation of the population to changing living conditions in the lung. Genomic diversification during chronic infection requires increased attention when new control strategies against M. abscessus infections are explored.
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Affiliation(s)
- Astrid Lewin
- Unit 16 Mycotic and Parasitic Agents and Mycobacteria, Robert Koch Institute, Berlin, Germany
| | - Elisabeth Kamal
- Unit 16 Mycotic and Parasitic Agents and Mycobacteria, Robert Koch Institute, Berlin, Germany
| | - Torsten Semmler
- Unit NG 1 Microbial Genomics, Robert Koch Institute, Berlin, Germany
| | - Katja Winter
- Unit MF1 Bioinformatics, Robert Koch Institute, Berlin, Germany
| | - Sandra Kaiser
- Unit MF1 Bioinformatics, Robert Koch Institute, Berlin, Germany
| | - Hubert Schäfer
- Unit 16 Mycotic and Parasitic Agents and Mycobacteria, Robert Koch Institute, Berlin, Germany
| | - Lei Mao
- Unit 16 Mycotic and Parasitic Agents and Mycobacteria, Robert Koch Institute, Berlin, Germany.,Unit 31 Infectious Disease Data Science Unit, Robert Koch Institute, Berlin, Germany
| | - Patience Eschenhagen
- Klinikum Westbrandenburg, Campus Potsdam, Cystic Fibrosis Section, Potsdam, Germany.,Pediatric Respiratory Medicine, Immunology and Intensive Care Medicine, Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Claudia Grehn
- Department of Pediatrics, Division of Pulmonology, Immunology and Intensive Care Medicine, Division of Cystic Fibrosis, Charité - Universitätsmedizin, Berlin, Germany
| | - Jennifer Bender
- Unit 13 Nosocomial Pathogens and Antibiotic Resistances, Robert Koch Institute, Wernigerode, Germany.,ECDC Fellowship Programme, Public Health Microbiology Path (EUPHEM), European Centre for Disease Prevention and Control (ECDC), Solna, Sweden
| | - Carsten Schwarz
- Klinikum Westbrandenburg, Campus Potsdam, Cystic Fibrosis Section, Potsdam, Germany.,Pediatric Respiratory Medicine, Immunology and Intensive Care Medicine, Charité Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
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9
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Giacalone D, Huang L, Tan S. Exploiting Fluorescent Proteins to Understand Mycobacterium tuberculosis Biology. Methods Mol Biol 2021; 2314:365-383. [PMID: 34235663 PMCID: PMC8381720 DOI: 10.1007/978-1-0716-1460-0_17] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
The utility of fluorescent proteins in bacterial research has long been appreciated, with extensive use in the Mycobacterium tuberculosis field. In more recent years, a new generation of fluorescent tools has been developed for use in M. tuberculosis research. These new fluorescent reporters exploit the immense genetic and transcriptional knowledge now available, and enable the use of the bacteria as direct reporters of the local environment during infection, as well as provide insight into bacterial replication status in situ. Here we describe methods for the construction of such fluorescent reporter M. tuberculosis strains, and their use in combination with confocal microscopy and flow cytometry approaches for single bacterium-level analyses of M. tuberculosis physiology and M. tuberculosis-host interactions.
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Affiliation(s)
- David Giacalone
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University, Boston, MA, USA
| | - Lu Huang
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Shumin Tan
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA.
- Graduate Program in Molecular Microbiology, Graduate School of Biomedical Sciences, Tufts University, Boston, MA, USA.
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10
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Fishbein SRS, Tomasi FG, Wolf ID, Dulberger CL, Wang A, Keshishian H, Wallace L, Carr SA, Ioerger TR, Rego EH, Rubin EJ. The conserved translation factor LepA is required for optimal synthesis of a porin family in Mycobacterium smegmatis. J Bacteriol 2020; 203:JB.00604-20. [PMID: 33361193 PMCID: PMC8095456 DOI: 10.1128/jb.00604-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 12/15/2020] [Indexed: 11/20/2022] Open
Abstract
The recalcitrance of mycobacteria to antibiotic therapy is in part due to its ability to build proteins into a multi-layer cell wall. Proper synthesis of both cell wall constituents and associated proteins is crucial to maintaining cell integrity, and intimately tied to antibiotic susceptibility. How mycobacteria properly synthesize the membrane-associated proteome, however, remains poorly understood. Recently, we found that loss of lepA in Mycobacterium smegmatis (Msm) altered tolerance to rifampin, a drug that targets a non-ribosomal cellular process. LepA is a ribosome-associated GTPase found in bacteria, mitochondria, and chloroplasts, yet its physiological contribution to cellular processes is not clear. To uncover the determinants of LepA-mediated drug tolerance, we characterized the whole-cell proteomes and transcriptomes of a lepA deletion mutant relative to strains with lepA We find that LepA is important for the steady-state abundance of a number of membrane-associated proteins, including an outer membrane porin, MspA, which is integral to nutrient uptake and drug susceptibility. Loss of LepA leads to a decreased amount of porin in the membrane which leads to the drug tolerance phenotype of the lepA mutant. In mycobacteria, the translation factor LepA modulates mycobacterial membrane homeostasis, which in turn affects antibiotic tolerance.ImportanceThe mycobacterial cell wall is a promising target for new antibiotics due to the abundance of important membrane-associated proteins. Defining mechanisms of synthesis of the membrane proteome will be critical to uncovering and validating drug targets. We found that LepA, a universally conserved translation factor, controls the synthesis of a number of major membrane proteins in M. smegmatis LepA primarily controls synthesis of the major porin MspA. Loss of LepA results in decreased permeability through the loss of this porin, including permeability to antibiotics like rifampin and vancomycin. In mycobacteria, regulation from the ribosome is critical for the maintenance of membrane homeostasis and, importantly, antibiotic susceptibility.
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Affiliation(s)
- Skye R S Fishbein
- Department of Immunology and Infectious Disease, Harvard TH Chan School of Public Health, Boston, Massachusetts, 02115, United States
| | - Francesca G Tomasi
- Department of Immunology and Infectious Disease, Harvard TH Chan School of Public Health, Boston, Massachusetts, 02115, United States
| | - Ian D Wolf
- Department of Immunology and Infectious Disease, Harvard TH Chan School of Public Health, Boston, Massachusetts, 02115, United States
| | - Charles L Dulberger
- Department of Immunology and Infectious Disease, Harvard TH Chan School of Public Health, Boston, Massachusetts, 02115, United States
| | - Albert Wang
- Department of Immunology and Infectious Disease, Harvard TH Chan School of Public Health, Boston, Massachusetts, 02115, United States
| | | | - Luke Wallace
- Broad Institute of MIT and Harvard, Cambridge, 02142, United States
| | - Steven A Carr
- Broad Institute of MIT and Harvard, Cambridge, 02142, United States
| | - Thomas R Ioerger
- Department of Computer Science and Engineering, Texas A&M University, Texas, 77843, United States
| | - E Hesper Rego
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, Connecticut, 06510, United States
| | - Eric J Rubin
- Department of Immunology and Infectious Disease, Harvard TH Chan School of Public Health, Boston, Massachusetts, 02115, United States
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11
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Qiu GW, Jiang HB, Lis H, Li ZK, Deng B, Shang JL, Sun CY, Keren N, Qiu BS. A unique porin meditates iron-selective transport through cyanobacterial outer membranes. Environ Microbiol 2020; 23:376-390. [PMID: 33196124 DOI: 10.1111/1462-2920.15324] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 11/02/2020] [Accepted: 11/12/2020] [Indexed: 10/23/2022]
Abstract
Cyanobacteria are globally important primary producers and nitrogen fixers with high iron demands. Low ambient dissolved iron concentrations in many aquatic environments mean that these organisms must maintain sufficient and selective transport of iron into the cell. However, the nature of iron transport pathways through the cyanobacterial outer membrane remains obscure. Here we present multiple lines of experimental evidence that collectively support the existence of a novel class of substrate-selective iron porin, Slr1908, in the outer membrane of the cyanobacterium Synechocystis sp. PCC 6803. Elemental composition analysis and short-term iron uptake assays with mutants in Slr1908 reveal that this protein is primarily involved in inorganic iron uptake and contributes less to the accumulation of other metals. Homologues of Slr1908 are widely distributed in both freshwater and marine cyanobacteria, most notably in unicellular marine diazotrophs. Complementary experiments with a homologue of Slr1908 in Synechococcus sp. PCC 7002 restored the phenotype of Synechocystis knockdown mutants, showing that this siderophore producing species also possesses a porin with a similar function in Fe transport. The involvement of a substrate-selective porins in iron uptake may allow cyanobacteria to tightly control iron flux into the cell, particularly in environments where iron concentrations fluctuate.
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Affiliation(s)
- Guo-Wei Qiu
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, China
| | - Hai-Bo Jiang
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, China
| | - Hagar Lis
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, Israel
| | - Zheng-Ke Li
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, China
| | - Bin Deng
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, China
| | - Jin-Long Shang
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, China
| | - Chuan-Yu Sun
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, China
| | - Nir Keren
- Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, Israel
| | - Bao-Sheng Qiu
- School of Life Sciences, Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan, China
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12
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Gerken H, Vuong P, Soparkar K, Misra R. Roles of the EnvZ/OmpR Two-Component System and Porins in Iron Acquisition in Escherichia coli. mBio 2020; 11:e01192-20. [PMID: 32576675 PMCID: PMC7315122 DOI: 10.1128/mbio.01192-20] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 05/19/2020] [Indexed: 12/31/2022] Open
Abstract
Escherichia coli secretes high-affinity Fe3+ chelators to solubilize and transport chelated Fe3+ via specific outer membrane receptors. In microaerobic and anaerobic growth environments, where the reduced Fe2+ form is predominant, ferrous transport systems fulfill the bacterial need for iron. Expression of genes coding for iron metabolism is controlled by Fur, which when bound to Fe2+ acts as a repressor. Work carried out here shows that the constitutively activated EnvZ/OmpR two-component system, which normally controls expression of the ompC and ompF porin genes, dramatically increases the intracellular pool of accessible iron, as determined by whole-cell electron paramagnetic resonance spectroscopy, by inducing the OmpC/FeoB-mediated ferrous transport pathway. Elevated levels of intracellular iron in turn activated Fur, which inhibited the ferric transport pathway but not the ferrous transport pathway. The data show that the positive effect of constitutively activated EnvZ/OmpR on feoB expression is sufficient to overcome the negative effect of activated Fur on feoB In a tonB mutant, which lacks functional ferric transport systems, deletion of ompR severely impairs growth on rich medium not supplemented with iron, while the simultaneous deletion of ompC and ompF is not viable. These data, together with the observation of derepression of the Fur regulon in an OmpC mutant, show that the porins play an important role in iron homeostasis. The work presented here also resolves a long-standing paradoxical observation of the effect of certain mutant envZ alleles on iron regulon.IMPORTANCE The work presented here solved a long-standing paradox of the negative effects of certain missense alleles of envZ, which codes for kinase of the EnvZ/OmpR two-component system, on the expression of ferric uptake genes. The data revealed that the constitutive envZ alleles activate the Feo- and OmpC-mediated ferrous uptake pathway to flood the cytoplasm with accessible ferrous iron. This activates the ferric uptake regulator, Fur, which inhibits ferric uptake system but cannot inhibit the feo operon due to the positive effect of activated EnvZ/OmpR. The data also revealed the importance of porins in iron homeostasis.
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Affiliation(s)
- Henri Gerken
- School of Life Sciences, Arizona State University, Tempe, Arizona, USA
| | - Phu Vuong
- School of Life Sciences, Arizona State University, Tempe, Arizona, USA
| | - Ketaki Soparkar
- School of Life Sciences, Arizona State University, Tempe, Arizona, USA
| | - Rajeev Misra
- School of Life Sciences, Arizona State University, Tempe, Arizona, USA
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13
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Kumar N, Sritharan M. Role of a 21-kDa iron-regulated protein IrpA in the uptake of ferri-exochelin by Mycobacterium smegmatis. J Appl Microbiol 2020; 129:1733-1743. [PMID: 32472729 DOI: 10.1111/jam.14728] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 05/17/2020] [Accepted: 05/25/2020] [Indexed: 11/30/2022]
Abstract
AIMS To characterize the 21-kDa iron-regulated cell wall protein in Mycobacterium smegmatis co-expressed with the siderophores mycobactin, exochelin and carboxymycobactin upon iron limitation. METHODS AND RESULTS Mycobacterium smegmatis, grown in the presence of 0·02 μg Fe ml-1 (low iron) produced high levels of all the three siderophores, which were repressed in bacteria supplemented with 8 μg Fe ml-1 (high iron). Exochelin, the major extracellular siderophore was the first to rise and was expressed at high levels during log phase of growth. Carboxymycobactin, a minor component in log phase iron-starved M. smegmatis continued to rise when cultured for longer periods, reaching levels greater than exochelin. Iron-starved bacteria expressed a 21-kDa iron-regulated protein (IrpA) that was identified as Clp protease subunit (MSMEG_3671) and characterized as a receptor for ferri-exochelin. CONCLUSIONS Ferri-exochelin is the preferred siderophore in M. smegmatis and this ferri-exochelin: IrpA machinery is absent in Mycobacterium tuberculosis. SIGNIFICANCE AND IMPACT OF THE STUDY Exochelin machinery is functional in M. smegmatis and the carboxymycobactin-mycobactin machinery is the sole iron uptake system in M. tuberculosis. The absence of the ferri-exochelin: IrpA system in the pathogen signifies the importance of the carboxymycobactin-mycobactin system machinery in M. tuberculosis.
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Affiliation(s)
- N Kumar
- Department of Animal Biology, University of Hyderabad, Hyderabad, Telangana, India
| | - M Sritharan
- Department of Animal Biology, University of Hyderabad, Hyderabad, Telangana, India
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14
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Abstract
Zinc homeostasis is crucial for bacterial cells, since imbalances affect viability. However, in mycobacteria, knowledge of zinc metabolism is incomplete. Mycobacterium smegmatis (MSMEG) is an environmental, nonpathogenic Mycobacterium that is widely used as a model organism to study mycobacterial metabolism and pathogenicity. How MSMEG maintains zinc homeostasis is largely unknown. SmtB and Zur are important regulators of bacterial zinc metabolism. In mycobacteria, these regulators are encoded by an operon, whereas in other bacterial species, SmtB and Zur are encoded on separate loci. Here, we show that the smtB-zur operon is consistently present within the genus Mycobacterium but otherwise found only in Nocardia, Saccharothrix, and Corynebacterium diphtheriae By RNA deep sequencing, we determined the Zur and SmtB regulons of MSMEG and compared them with transcriptional responses after zinc starvation or excess. We found an exceptional genomic clustering of genes whose expression was strongly induced by zur deletion and zinc starvation. These genes encoded zinc importers such as ZnuABC and three additional putative zinc transporters, including the porin MspD, as well as alternative ribosomal proteins. In contrast, only a few genes were affected by deletion of smtB and zinc excess. The zinc exporter ZitA was most prominently regulated by SmtB. Moreover, transcriptional analyses in combination with promoter and chromatin immunoprecipitation assays revealed a special regulation of the smtB-zur operon itself: an apparently zinc-independent, constitutive expression of smtB-zur resulted from sensitive coregulation by both SmtB and Zur. Overall, our data revealed yet unknown peculiarities of mycobacterial zinc homeostasis.IMPORTANCE Zinc is crucial for many biological processes, as it is an essential cofactor of enzymes and a structural component of regulatory and DNA binding proteins. Hence, all living cells require zinc to maintain constant intracellular levels. However, in excess, zinc is toxic. Therefore, cellular zinc homeostasis needs to be tightly controlled. In bacteria, this is achieved by transcriptional regulators whose activity is mediated via zinc-dependent conformational changes promoting or preventing their binding to DNA. SmtB and Zur are important antagonistically acting bacterial regulators in mycobacteria. They sense changes in zinc concentrations in the femtomolar range and regulate transcription of genes for zinc acquisition, storage, and export. Here, we analyzed the role of SmtB and Zur in zinc homeostasis in Mycobacterium smegmatis Our results revealed novel insights into the transcriptional processes of zinc homeostasis in mycobacteria and their regulation.
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15
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Dragset MS, Ioerger TR, Zhang YJ, Mærk M, Ginbot Z, Sacchettini JC, Flo TH, Rubin EJ, Steigedal M. Genome-wide Phenotypic Profiling Identifies and Categorizes Genes Required for Mycobacterial Low Iron Fitness. Sci Rep 2019; 9:11394. [PMID: 31388080 PMCID: PMC6684656 DOI: 10.1038/s41598-019-47905-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 07/18/2019] [Indexed: 11/26/2022] Open
Abstract
Iron is vital for nearly all living organisms, but during infection, not readily available to pathogens. Infectious bacteria therefore depend on specialized mechanisms to survive when iron is limited. These mechanisms make attractive targets for new drugs. Here, by genome-wide phenotypic profiling, we identify and categorize mycobacterial genes required for low iron fitness. Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), can scavenge host-sequestered iron by high-affinity iron chelators called siderophores. We take advantage of siderophore redundancy within the non-pathogenic mycobacterial model organism M. smegmatis (Msmeg), to identify genes required for siderophore dependent and independent fitness when iron is low. In addition to genes with a potential function in recognition, transport or utilization of mycobacterial siderophores, we identify novel putative low iron survival strategies that are separate from siderophore systems. We also identify the Msmeg in vitro essential gene set, and find that 96% of all growth-required Msmeg genes have a mutual ortholog in Mtb. Of these again, nearly 90% are defined as required for growth in Mtb as well. Finally, we show that a novel, putative ferric iron ABC transporter contributes to low iron fitness in Msmeg, in a siderophore independent manner.
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Affiliation(s)
- Marte S Dragset
- NTNU Norwegian University of Science and Technology, Centre of Molecular Inflammation Research and Department of Clinical and Molecular Medicine, Trondheim, 7491, Norway. .,Harvard T.H. Chan School of Public Health, Department of Immunology and Infectious Diseases, Boston, MA, 02115, USA. .,Germans Trias i Pujol Research Institute, Tuberculosis Research Unit, Badalona, 80916, Spain.
| | - Thomas R Ioerger
- Texas A&M University, Department of Computer Science, College Station, TX, 77843, USA
| | - Yanjia J Zhang
- Harvard T.H. Chan School of Public Health, Department of Immunology and Infectious Diseases, Boston, MA, 02115, USA
| | - Mali Mærk
- NTNU Norwegian University of Science and Technology, Centre of Molecular Inflammation Research and Department of Clinical and Molecular Medicine, Trondheim, 7491, Norway
| | - Zekarias Ginbot
- NTNU Norwegian University of Science and Technology, Centre of Molecular Inflammation Research and Department of Clinical and Molecular Medicine, Trondheim, 7491, Norway
| | - James C Sacchettini
- Texas A&M University, Department of Biochemistry and Biophysics, College Station, TX, 77843, USA
| | - Trude H Flo
- NTNU Norwegian University of Science and Technology, Centre of Molecular Inflammation Research and Department of Clinical and Molecular Medicine, Trondheim, 7491, Norway
| | - Eric J Rubin
- Harvard T.H. Chan School of Public Health, Department of Immunology and Infectious Diseases, Boston, MA, 02115, USA
| | - Magnus Steigedal
- NTNU Norwegian University of Science and Technology, Centre of Molecular Inflammation Research and Department of Clinical and Molecular Medicine, Trondheim, 7491, Norway.,Harvard T.H. Chan School of Public Health, Department of Immunology and Infectious Diseases, Boston, MA, 02115, USA.,St. Olavs University Hospital, Department of Medical Microbiology, Trondheim, 7030, Norway
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16
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Using a Chemical Genetic Screen to Enhance Our Understanding of the Antimicrobial Properties of Gallium against Escherichia coli. Genes (Basel) 2019; 10:genes10010034. [PMID: 30634525 PMCID: PMC6356860 DOI: 10.3390/genes10010034] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 12/17/2018] [Accepted: 01/04/2019] [Indexed: 12/13/2022] Open
Abstract
The diagnostic and therapeutic agent gallium offers multiple clinical and commercial uses including the treatment of cancer and the localization of tumors, among others. Further, this metal has been proven to be an effective antimicrobial agent against a number of microbes. Despite the latter, the fundamental mechanisms of gallium action have yet to be fully identified and understood. To further the development of this antimicrobial, it is imperative that we understand the mechanisms by which gallium interacts with cells. As a result, we screened the Escherichia coli Keio mutant collection as a means of identifying the genes that are implicated in prolonged gallium toxicity or resistance and mapped their biological processes to their respective cellular system. We discovered that the deletion of genes functioning in response to oxidative stress, DNA or iron–sulfur cluster repair, and nucleotide biosynthesis were sensitive to gallium, while Ga resistance comprised of genes involved in iron/siderophore import, amino acid biosynthesis and cell envelope maintenance. Altogether, our explanations of these findings offer further insight into the mechanisms of gallium toxicity and resistance in E. coli.
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17
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Nath Y, Ray SK, Buragohain AK. Essential role of the ESX-3 associated eccD3 locus in maintaining the cell wall integrity of Mycobacterium smegmatis. Int J Med Microbiol 2018; 308:784-795. [PMID: 30257807 DOI: 10.1016/j.ijmm.2018.06.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 05/21/2018] [Accepted: 06/24/2018] [Indexed: 11/28/2022] Open
Abstract
Mycobacterial pathogens have evolved a unique secretory apparatus called the Type VII secretion system (T7SS) which comprises of five gene clusters designated as ESX1, ESX2, ESX3, ESX4, and ESX5. Of these the ESX3 T7SS plays an important role in the regulatory uptake of iron from the environment, thereby enabling the bacteria to establish successful infection in the host. However, ESX3 secretion system is conserved among all the mycobacterial species including the fast-growing nonpathogenic species M. smegmatis. Although the function of ESX3 T7SS is known to be absolutely critical for establishing infection by M. tuberculosis, its conserved nature in all the pathogenic and nonpathogenic mycobacterial species intrigues to explore the additional functional roles in Mycobacterium species through which potent targets for drugs can be identified and developed. In the present study, we investigated the possible role of EccD3, a transmembrane protein of the ESX3 T7SS in M. smegmatis by deleting the entire eccD3 gene by efficient allelic exchange method. The preliminary investigations through the creation of knockout mutant of the eccD3 gene indicate that this secretory apparatus has an important role in maintaining the cell wall integrity which was evident from the abnormal colony morphology, lack of biofilm formation and difference in cell wall permeability.
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Affiliation(s)
- Yutika Nath
- Department of Molecular Biology and Biotechnology, Tezpur University, Napaam, Tezpur, Assam, 784028, India.
| | - Suvendra Kumar Ray
- Department of Molecular Biology and Biotechnology, Tezpur University, Napaam, Tezpur, Assam, 784028, India.
| | - Alak Kumar Buragohain
- Department of Molecular Biology and Biotechnology, Tezpur University, Napaam, Tezpur, Assam, 784028, India; Dibrugarh University, Dibrugarh, Assam, 786004, India.
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18
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Outer Membrane Iron Uptake Pathways in the Model Cyanobacterium Synechocystis sp. Strain PCC 6803. Appl Environ Microbiol 2018; 84:AEM.01512-18. [PMID: 30076192 DOI: 10.1128/aem.01512-18] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 07/21/2018] [Indexed: 02/01/2023] Open
Abstract
Cyanobacteria are foundational drivers of global nutrient cycling, with high intracellular iron (Fe) requirements. Fe is found at extremely low concentrations in aquatic systems, however, and the ways in which cyanobacteria take up Fe are largely unknown, especially the initial step in Fe transport across the outer membrane. Here, we identified one TonB protein and four TonB-dependent transporters (TBDTs) of the energy-requiring Fe acquisition system and six porins of the passive diffusion Fe uptake system in the model cyanobacterium Synechocystis sp. strain PCC 6803. The results experimentally demonstrated that TBDTs not only participated in organic ferri-siderophore uptake but also in inorganic free Fe (Fe') acquisition. 55Fe uptake rate measurements showed that a TBDT quadruple mutant acquired Fe at a lower rate than the wild type and lost nearly all ability to take up ferri-siderophores, indicating that TBDTs are critical for siderophore uptake. However, the mutant retained the ability to take up Fe' at 42% of the wild-type Fe' uptake rate, suggesting additional pathways of Fe' acquisition besides TBDTs, likely by porins. Mutations in four of the six porin-encoding genes produced a low-Fe-sensitive phenotype, while a mutation in all six genes was lethal to cell survival. These diverse outer membrane Fe uptake pathways reflect cyanobacterial evolution and adaptation under a range of Fe regimes across aquatic systems.IMPORTANCE Cyanobacteria are globally important primary producers and contribute about 25% of global CO2 fixation. Low Fe bioavailability in surface waters is thought to limit the primary productivity in as much as 40% of the global ocean. The Fe acquisition strategies that cyanobacteria have evolved to overcome Fe deficiency remain poorly characterized. We experimentally characterized the key players and the cooperative work mode of two Fe uptake pathways, including an active uptake pathway and a passive diffusion pathway in the model cyanobacterium Synechocystis sp. PCC 6803. Our finding proved that cyanobacteria use ferri-siderophore transporters to take up Fe', and they shed light on the adaptive mechanisms of cyanobacteria to cope with widespread Fe deficiency across aquatic environments.
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19
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Abramovitch RB. Mycobacterium tuberculosis Reporter Strains as Tools for Drug Discovery and Development. IUBMB Life 2018; 70:818-825. [PMID: 29707888 DOI: 10.1002/iub.1862] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 04/08/2018] [Indexed: 11/11/2022]
Abstract
Reporter strains have proven to be powerful tools to study Mycobacterium tuberculosis (Mtb) physiology. Transcriptional and translational reporter strains are engineered by fusing a readout gene, encoding a fluorescent, luminescent or enzymatic protein, downstream of a promoter or in-frame with a gene of interest. When the reporter is expressed, it generates a signal that acts as a synthetic phenotype, enabling the study of physiologies that might have otherwise been hidden. This review will discuss approaches for generating reporter strains in Mtb and how they can be used as tools for high-throughput genetic and small molecule screening and as biomarkers for examining Mtb responses to drug or immune stresses during animal infections. Fluorescent reporter strains have an added benefit in that they can be used for single-cell studies both in vitro and in vivo, thus enabling the study of mechanisms underlying phenotypic heterogeneity. Recent examples of the use of Mtb reporter strains will be presented with a focus on how they can be used as tools for drug discovery and development. © 2018 IUBMB Life, 70(9):818-825, 2018.
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Affiliation(s)
- Robert B Abramovitch
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
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20
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Trovero MF, Scavone P, Platero R, de Souza EM, Fabiano E, Rosconi F. Herbaspirillum seropedicae Differentially Expressed Genes in Response to Iron Availability. Front Microbiol 2018; 9:1430. [PMID: 30018605 PMCID: PMC6037834 DOI: 10.3389/fmicb.2018.01430] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 06/11/2018] [Indexed: 01/20/2023] Open
Abstract
Herbaspirillum seropedicae Z67 is a nitrogen-fixing endophyte that colonizes many important crops. Like in almost all organisms, vital cellular processes of this endophyte are iron dependent. In order to efficiently acquire iron to fulfill its requirements, this bacterium produces the siderophores serobactins. However, the presence in its genome of many others iron acquisition genes suggests that serobactins are not the only strategy used by H. seropedicae to overcome metal deficiency. The aim of this work was to identify genes and proteins differentially expressed by cells growing in low iron conditions in order to describe H. seropedicae response to iron limitation stress. For this purpose, and by using a transcriptomic approach, we searched and identified a set of genes up-regulated when iron was scarce. One of them, Hsero_2337, codes for a TonB-dependent transporter/transducer present in the serobactins biosynthesis genomic locus, with an unknown function. Another TonB-dependent receptor, the one encoded by Hsero_1277, and an inner membrane ferrous iron permease, coded by Hsero_2720, were also detected. By using a proteomic approach focused in membrane proteins, we identified the specific receptor for iron-serobactin internalization SbtR and two non-characterized TonB-dependent receptors (coded by genes Hsero_1277 and Hsero_3255). We constructed mutants on some of the identified genes and characterized them by in vitro growth, biofilm formation, and interaction with rice plants. Characterization of mutants in gene Hsero_2337 showed that the TonB-dependent receptor coded by this gene has a regulatory role in the biosynthesis of serobactins, probably by interacting with the alternative sigma factor PfrI, coded by gene Hsero_2338. Plant colonization of the mutant strains was not affected, since the mutant strain normally colonize the root and aerial part of rice plants. These results suggest that the strategies used by H. seropedicae to acquire iron inside plants are far more diverse than the ones characterized in this work. In vivo expression studies or colonization competition experiments between the different mutant strains could help us in future works to determine the relative importance of the different iron acquisition systems in the interaction of H. seropedicae with rice plants.
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Affiliation(s)
- María F Trovero
- Departamento de Bioquímica y Genómica Microbianas, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
| | - Paola Scavone
- Departamento de Microbiología, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
| | - Raúl Platero
- Departamento de Bioquímica y Genómica Microbianas, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
| | - Emanuel M de Souza
- Departamento de Bioquimica e Biologia Molecular, Universidade Federal do Paraná, Curitiba, Brazil
| | - Elena Fabiano
- Departamento de Bioquímica y Genómica Microbianas, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
| | - Federico Rosconi
- Departamento de Bioquímica y Genómica Microbianas, Instituto de Investigaciones Biológicas Clemente Estable, Montevideo, Uruguay
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21
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Stanborough T, Fegan N, Powell SM, Tamplin M, Chandry PS. Vibrioferrin production by the food spoilage bacterium Pseudomonas fragi. FEMS Microbiol Lett 2018; 365:4768089. [PMID: 29272380 DOI: 10.1093/femsle/fnx279] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 12/18/2017] [Indexed: 11/13/2022] Open
Abstract
Pseudomonas fragi is a meat and milk spoilage bacterium with high iron requirements; however, mechanisms of iron acquisition remain largely unknown. The aim of this work was to investigate siderophore production as an iron acquisition system for P. fragi. A vibrioferrin siderophore gene cluster was identified in 13 P. fragi, and experiments were conducted with a representative strain of this group (F1801). Chromeazurol S assays showed that P. fragi F1801 produced siderophores under iron starvation at optimum growth and refrigeration temperature. Conversely, supplementation of low iron media with 50 μM FeCl3 repressed transcription of the vibrioferrin genes and siderophore production. Disruption of the siderophore receptor (pvuA) caused polar effects on downstream vibrioferrin genes, resulting in impaired siderophore production of the ΔpvuA mutant. Growth of this mutant was compared to growth of a control strain (Δlip) with wild-type vibrioferrin genes in low iron media supplemented with iron chelators 2,2΄-bipyridyl or apo-transferrin. While 25 μM 2,2΄-bipyridyl caused impaired growth of ΔpvuA, growth of the mutant was completely inhibited by 2.5 μM apo-transferrin, but could be restored by FeCl3 addition. In summary, this work identifies a vibrioferrin-mediated iron acquisition system of P. fragi, which is required for growth of this bacterium under iron starvation.
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Affiliation(s)
- Tamsyn Stanborough
- CSIRO Agriculture and Food, Werribee, VIC 3030, Australia.,Centre for Food Safety and Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, TAS 7001, Australia
| | - Narelle Fegan
- CSIRO Agriculture and Food, Werribee, VIC 3030, Australia
| | - Shane M Powell
- Centre for Food Safety and Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, TAS 7001, Australia
| | - Mark Tamplin
- Centre for Food Safety and Innovation, Tasmanian Institute of Agriculture, University of Tasmania, Hobart, TAS 7001, Australia
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22
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Moumène A, Gonzalez-Rizzo S, Lefrançois T, Vachiéry N, Meyer DF. Iron Starvation Conditions Upregulate Ehrlichia ruminantium Type IV Secretion System, tr1 Transcription Factor and map1 Genes Family through the Master Regulatory Protein ErxR. Front Cell Infect Microbiol 2018; 7:535. [PMID: 29404278 PMCID: PMC5780451 DOI: 10.3389/fcimb.2017.00535] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 12/22/2017] [Indexed: 11/13/2022] Open
Abstract
Ehrlichia ruminantium is an obligatory intracellular bacterium that causes heartwater, a fatal disease in ruminants. Due to its intracellular nature, E. ruminantium requires a set of specific virulence factors, such as the type IV secretion system (T4SS), and outer membrane proteins (Map proteins) in order to avoid and subvert the host's immune response. Several studies have been conducted to understand the regulation of the T4SS or outer membrane proteins, in Ehrlichia, but no integrated approach has been used to understand the regulation of Ehrlichia pathogenicity determinants in response to environmental cues. Iron is known to be a key nutrient for bacterial growth both in the environment and within hosts. In this study, we experimentally demonstrated the regulation of virB, map1, and tr1 genes by the newly identified master regulator ErxR (for Ehrlichia ruminantium expression regulator). We also analyzed the effect of iron depletion on the expression of erxR gene, tr1 transcription factor, T4SS and map1 genes clusters in E. ruminantium. We show that exposure of E. ruminantium to iron starvation induces erxR and subsequently tr1, virB, and map1 genes. Our results reveal tight co-regulation of T4SS and map1 genes via the ErxR regulatory protein at the transcriptional level, and, for the first time link map genes to the virulence function sensu stricto, thereby advancing our understanding of Ehrlichia's infection process. These results suggest that Ehrlichia is able to sense changes in iron concentrations in the environment and to regulate the expression of virulence factors accordingly.
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Affiliation(s)
- Amal Moumène
- Centre de Coopération Internationale en Recherche Agronomique Pour le Développement, UMR ASTRE, Petit-Bourg, France.,ASTRE, Univ Montpellier, Centre de Coopération Internationale en Recherche Agronomique Pour le Développement, Institut National de la Recherche Agronomique, Montpellier, France.,UFR Sciences Exactes et Naturelles, Université des Antilles, Pointe-à-Pitre, France
| | - Silvina Gonzalez-Rizzo
- Institut de Biologie Paris Seine (EPS - IBPS), Sorbonne Universités, UPMC Univ Paris 06, Univ Antilles, Univ Nice Sophia Antipolis, Centre National de la Recherche Scientifique Evolution Paris Seine, Paris, France.,Equipe Biologie de la Mangrove, UFR Sciences Exactes et Naturelles, Université des Antilles, Pointe-à-Pitre, France
| | - Thierry Lefrançois
- Centre de Coopération Internationale en Recherche Agronomique Pour le Développement, UMR ASTRE, Petit-Bourg, France.,ASTRE, Univ Montpellier, Centre de Coopération Internationale en Recherche Agronomique Pour le Développement, Institut National de la Recherche Agronomique, Montpellier, France
| | - Nathalie Vachiéry
- Centre de Coopération Internationale en Recherche Agronomique Pour le Développement, UMR ASTRE, Petit-Bourg, France.,ASTRE, Univ Montpellier, Centre de Coopération Internationale en Recherche Agronomique Pour le Développement, Institut National de la Recherche Agronomique, Montpellier, France
| | - Damien F Meyer
- Centre de Coopération Internationale en Recherche Agronomique Pour le Développement, UMR ASTRE, Petit-Bourg, France.,ASTRE, Univ Montpellier, Centre de Coopération Internationale en Recherche Agronomique Pour le Développement, Institut National de la Recherche Agronomique, Montpellier, France
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23
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Pandey SS, Patnana PK, Rai R, Chatterjee S. Xanthoferrin, the α-hydroxycarboxylate-type siderophore of Xanthomonas campestris pv. campestris, is required for optimum virulence and growth inside cabbage. MOLECULAR PLANT PATHOLOGY 2017; 18:949-962. [PMID: 27348422 PMCID: PMC6638303 DOI: 10.1111/mpp.12451] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 06/10/2016] [Accepted: 06/23/2016] [Indexed: 05/27/2023]
Abstract
Xanthomonas campestris pv. campestris causes black rot, a serious disease of crucifers. Xanthomonads encode a siderophore biosynthesis and uptake gene cluster xss (Xanthomonas siderophore synthesis) involved in the production of a vibrioferrin-type siderophore. However, little is known about the role of the siderophore in the iron uptake and virulence of X. campestris pv. campestris. In this study, we show that X. campestris pv. campestris produces an α-hydroxycarboxylate-type siderophore (named xanthoferrin), which is required for growth under low-iron conditions and for optimum virulence. A mutation in the siderophore synthesis xssA gene causes deficiency in siderophore production and growth under low-iron conditions. In contrast, the siderophore utilization ΔxsuA mutant is able to produce siderophore, but exhibits a defect in the utilization of the siderophore-iron complex. Our radiolabelled iron uptake studies confirm that the ΔxssA and ΔxsuA mutants exhibit defects in ferric iron (Fe3+ ) uptake. The ΔxssA mutant is able to utilize and transport the exogenous xanthoferrin-Fe3+ complex; in contrast, the siderophore utilization or uptake mutant ΔxsuA exhibits defects in siderophore uptake. Expression analysis of the xss operon using a chromosomal gusA fusion indicates that the xss operon is expressed during in planta growth and under low-iron conditions. Furthermore, exogenous iron supplementation in cabbage leaves rescues the in planta growth deficiency of ΔxssA and ΔxsuA mutants. Our study reveals that the siderophore xanthoferrin is an important virulence factor of X. campestris pv. campestris which promotes in planta growth by the sequestration of Fe3+ .
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Affiliation(s)
- Sheo Shankar Pandey
- Centre for DNA Fingerprinting and Diagnostics, NampallyHyderabad500001India
- Graduate StudiesManipal UniversityManipal 576104India
| | | | - Rikky Rai
- Centre for DNA Fingerprinting and Diagnostics, NampallyHyderabad500001India
- Graduate StudiesManipal UniversityManipal 576104India
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Khare G, Nangpal P, Tyagi AK. Differential Roles of Iron Storage Proteins in Maintaining the Iron Homeostasis in Mycobacterium tuberculosis. PLoS One 2017; 12:e0169545. [PMID: 28060867 PMCID: PMC5218490 DOI: 10.1371/journal.pone.0169545] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 12/19/2016] [Indexed: 02/01/2023] Open
Abstract
Ferritins and bacterioferritins are iron storage proteins that represent key players in iron homeostasis. Several organisms possess both forms of ferritins, however, their relative physiological roles are less understood. Mycobacterium tuberculosis possesses both ferritin (BfrB) and bacterioferritin (BfrA), playing an essential role in its pathogenesis as reported by us earlier. This study provides insights into the role of these two proteins in iron homeostasis by employing M. tuberculosis bfr mutants. Our data suggests that BfrA is required for efficient utilization of stored iron under low iron conditions while BfrB plays a crucial role as the major defense protein under excessive iron conditions. We show that these two proteins provide protection against oxidative stress and hypoxia. Iron incorporation study showed that BfrB has higher capacity for storing iron than BfrA, which augurs well for efficient iron quenching under iron excess conditions. Moreover, iron release assay demonstrated that BfrA has 3 times superior ability to release stored iron emphasizing its requirement for efficient iron release under low iron conditions, facilitated by the presence of heme. Thus, for the first time, our observations suggest that the importance of BfrA or BfrB separately might vary depending upon the iron situation faced by the cell.
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Affiliation(s)
- Garima Khare
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi, India
| | - Prachi Nangpal
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi, India
| | - Anil K. Tyagi
- Department of Biochemistry, University of Delhi South Campus, Benito Juarez Road, New Delhi, India
- Vice Chancellor, Guru Gobind Singh Indraprastha University, Sector 16-C, Dwarka New Delhi, India
- * E-mail:
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Magro M, Fasolato L, Bonaiuto E, Andreani NA, Baratella D, Corraducci V, Miotto G, Cardazzo B, Vianello F. Enlightening mineral iron sensing in Pseudomonas fluorescens by surface active maghemite nanoparticles: Involvement of the OprF porin. Biochim Biophys Acta Gen Subj 2016; 1860:2202-10. [DOI: 10.1016/j.bbagen.2016.05.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 04/18/2016] [Accepted: 05/03/2016] [Indexed: 01/05/2023]
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Role of Metal-Dependent Regulation of ESX-3 Secretion in Intracellular Survival of Mycobacterium tuberculosis. Infect Immun 2016; 84:2255-2263. [PMID: 27245412 DOI: 10.1128/iai.00197-16] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 05/19/2016] [Indexed: 12/31/2022] Open
Abstract
More people die every year from Mycobacterium tuberculosis infection than from infection by any other bacterial pathogen. Type VII secretion systems (T7SS) are used by both environmental and pathogenic mycobacteria to secrete proteins across their complex cell envelope. In the nonpathogen Mycobacterium smegmatis, the ESX-1 T7SS plays a role in conjugation, and the ESX-3 T7SS is involved in metal homeostasis. In M. tuberculosis, these secretion systems have taken on roles in virulence, and they also are targets of the host immune response. ESX-3 secretes a heterodimer composed of EsxG (TB9.8) and EsxH (TB10.4), which impairs phagosome maturation in macrophages and is essential for virulence in mice. Given the importance of EsxG and EsxH during infection, we examined their regulation. With M. tuberculosis, the secretion of EsxG and EsxH was regulated in response to iron and zinc, in accordance with the previously described transcriptional response of the esx-3 locus to these metals. While iron regulated the esx-3 expression in both M. tuberculosis and M. smegmatis, there is a significant difference in the dynamics of this regulation. In M. smegmatis, the esx-3 locus behaved like other iron-regulated genes such as mbtB In M. tuberculosis, both iron and zinc modestly repressed esx-3 expression. Diminished secretion of EsxG and EsxH in response to these metals altered the interaction of M. tuberculosis with macrophages, leading to impaired intracellular M. tuberculosis survival. Our findings detail the regulatory differences of esx-3 in M. tuberculosis and M. smegmatis and demonstrate the importance of metal-dependent regulation of ESX-3 for virulence in M. tuberculosis.
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Pérez N, Johnson R, Sen B, Ramakrishnan G. Two parallel pathways for ferric and ferrous iron acquisition support growth and virulence of the intracellular pathogen Francisella tularensis Schu S4. Microbiologyopen 2016; 5:453-68. [PMID: 26918301 PMCID: PMC4905997 DOI: 10.1002/mbo3.342] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 01/10/2016] [Accepted: 01/14/2016] [Indexed: 12/17/2022] Open
Abstract
Iron acquisition mechanisms in Francisella tularensis, the causative agent of tularemia, include the Francisella siderophore locus (fsl) siderophore operon and a ferrous iron–transport system comprising outer‐membrane protein FupA and inner‐membrane transporter FeoB. To characterize these mechanisms and to identify any additional iron uptake systems in the virulent subspecies tularensis, single and double deletions were generated in the fsl and feo iron acquisition systems of the strain Schu S4. Deletion of the entire fsl operon caused loss of siderophore production that could be restored by complementation with the biosynthetic genes fslA and fslC and Major Facilitator Superfamily (MFS) transporter gene fslB. 55Fe‐transport assays demonstrated that siderophore‐iron uptake required the receptor FslE and MFS transporter FslD. A ΔfeoB′ mutation resulted in loss of ability to transport ferrous iron (55Fe2+). A ΔfeoB′ ΔfslA mutant that required added exogenous siderophore for growth in vitro was unable to grow within tissue culture cells and was avirulent in mice, indicating that no compensatory cryptic iron uptake systems were induced in vivo. These studies demonstrate that the fsl and feo pathways function independently and operate in parallel to effectively support virulence of F. tularensis.
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Affiliation(s)
- Natalie Pérez
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, 22908
| | - Richard Johnson
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, 22908
| | - Bhaswati Sen
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, 22908
| | - Girija Ramakrishnan
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, 22908
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Roe KL, Barbeau KA. Uptake mechanisms for inorganic iron and ferric citrate in Trichodesmium erythraeum IMS101. Metallomics 2015; 6:2042-51. [PMID: 25222699 DOI: 10.1039/c4mt00026a] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Growth of the prevalent marine organism Trichodesmium can be limited by iron in natural and laboratory settings. This study investigated the iron uptake mechanisms that the model organism T. erythraeum IMS101 uses to acquire iron from inorganic iron and iron associated with the weak ligand complex, ferric citrate. IMS101 was observed to employ two different iron uptake mechanisms: superoxide-mediated reduction of inorganic iron in the surrounding milieu and a superoxide-independent uptake system for ferric citrate complexes. While the detailed pathway of ferric citrate utilization remains to be elucidated, transport of iron from this complex appears to involve reduction and/or exchange of the iron out of the complex prior to uptake, either at the outer membrane of the cell or within the periplasmic space. Various iron uptake strategies may allow Trichodesmium to effectively scavenge iron in oligotrophic ocean environments.
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Affiliation(s)
- Kelly L Roe
- Geoscience Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA.
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29
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Ates LS, Ummels R, Commandeur S, van der Weerd R, Sparrius M, Weerdenburg E, Alber M, Kalscheuer R, Piersma SR, Abdallah AM, Abd El Ghany M, Abdel-Haleem AM, Pain A, Jiménez CR, Bitter W, Houben EN. Essential Role of the ESX-5 Secretion System in Outer Membrane Permeability of Pathogenic Mycobacteria. PLoS Genet 2015; 11:e1005190. [PMID: 25938982 PMCID: PMC4418733 DOI: 10.1371/journal.pgen.1005190] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Accepted: 04/02/2015] [Indexed: 12/03/2022] Open
Abstract
Mycobacteria possess different type VII secretion (T7S) systems to secrete proteins across their unusual cell envelope. One of these systems, ESX-5, is only present in slow-growing mycobacteria and responsible for the secretion of multiple substrates. However, the role of ESX-5 substrates in growth and/or virulence is largely unknown. In this study, we show that esx-5 is essential for growth of both Mycobacterium marinum and Mycobacterium bovis. Remarkably, this essentiality can be rescued by increasing the permeability of the outer membrane, either by altering its lipid composition or by the introduction of the heterologous porin MspA. Mutagenesis of the first nucleotide-binding domain of the membrane ATPase EccC5 prevented both ESX-5-dependent secretion and bacterial growth, but did not affect ESX-5 complex assembly. This suggests that the rescuing effect is not due to pores formed by the ESX-5 membrane complex, but caused by ESX-5 activity. Subsequent proteomic analysis to identify crucial ESX-5 substrates confirmed that all detectable PE and PPE proteins in the cell surface and cell envelope fractions were routed through ESX-5. Additionally, saturated transposon-directed insertion-site sequencing (TraDIS) was applied to both wild-type M. marinum cells and cells expressing mspA to identify genes that are not essential anymore in the presence of MspA. This analysis confirmed the importance of esx-5, but we could not identify essential ESX-5 substrates, indicating that multiple of these substrates are together responsible for the essentiality. Finally, examination of phenotypes on defined carbon sources revealed that an esx-5 mutant is strongly impaired in the uptake and utilization of hydrophobic carbon sources. Based on these data, we propose a model in which the ESX-5 system is responsible for the transport of cell envelope proteins that are required for nutrient uptake. These proteins might in this way compensate for the lack of MspA-like porins in slow-growing mycobacteria.
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Affiliation(s)
- Louis S. Ates
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Roy Ummels
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Susanna Commandeur
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Robert van der Weerd
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Marion Sparrius
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Eveline Weerdenburg
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
| | - Marina Alber
- Institute for Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Rainer Kalscheuer
- Institute for Medical Microbiology and Hospital Hygiene, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany
| | - Sander R. Piersma
- Department of Medical Oncology, OncoProteomics Laboratory, VU University Medical Center, Amsterdam, the Netherlands
| | - Abdallah M. Abdallah
- Biological and Environmental Sciences and Engineering (BESE) division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Moataz Abd El Ghany
- Biological and Environmental Sciences and Engineering (BESE) division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Alyaa M. Abdel-Haleem
- Biological and Environmental Sciences and Engineering (BESE) division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Arnab Pain
- Biological and Environmental Sciences and Engineering (BESE) division, King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia
| | - Connie R. Jiménez
- Department of Medical Oncology, OncoProteomics Laboratory, VU University Medical Center, Amsterdam, the Netherlands
| | - Wilbert Bitter
- Department of Medical Microbiology and Infection Control, VU University Medical Center, Amsterdam, the Netherlands
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicine & Systems, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
| | - Edith N.G. Houben
- Section Molecular Microbiology, Amsterdam Institute of Molecules, Medicine & Systems, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands
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A novel antimycobacterial compound acts as an intracellular iron chelator. Antimicrob Agents Chemother 2015; 59:2256-64. [PMID: 25645825 DOI: 10.1128/aac.05114-14] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Efficient iron acquisition is crucial for the pathogenesis of Mycobacterium 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 against M. tuberculosis have 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.
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31
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Fang Z, Sampson SL, Warren RM, Gey van Pittius NC, Newton-Foot M. Iron acquisition strategies in mycobacteria. Tuberculosis (Edinb) 2015; 95:123-30. [PMID: 25636179 DOI: 10.1016/j.tube.2015.01.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 01/01/2015] [Accepted: 01/07/2015] [Indexed: 02/04/2023]
Abstract
Iron is an essential element to most life forms including mycobacterial species. However, in the oxidative atmosphere iron exists as insoluble salts. Free and soluble iron ions are scarce in both the extracellular and intracellular environment which makes iron assimilation very challenging to mycobacteria. Tuberculosis, caused by the pathogen, Mycobacterium tuberculosis, is one of the most infectious and deadly diseases in the world. Extensive studies regarding iron acquisition strategies have been documented in mycobacteria, including work on the mycobacterial iron chelators (siderophores), the iron-responsive regulon, and iron transport and utilization pathways. Under low iron conditions, expression of the genes encoding iron importers, exporters and siderophore biosynthetic enzymes is up-regulated significantly increasing the ability of the bacteria to acquire limited host iron. Disabling these proteins impairs the growth of mycobacteria under low iron conditions both in vitro and in vivo, and that of pathogenic mycobacteria in animal models. Drugs targeting siderophore-mediated iron transport could offer promising therapeutic options. However, the discovery and characterization of an alternative iron acquisition mechanism, the heme transport and utilization pathway, questions the effectiveness of the siderophore-centered therapeutic strategy. Links have been found between these two distinct iron acquisition mechanisms, thus, targeting a few candidate proteins or mechanisms may influence both pathways, leading to effective elimination of the bacteria in the host.
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Affiliation(s)
- Zhuo Fang
- DST/NRF Centre of Excellence in Biomedical Tuberculosis Research, US/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
| | - Samantha Leigh Sampson
- DST/NRF Centre of Excellence in Biomedical Tuberculosis Research, US/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
| | - Robin Mark Warren
- DST/NRF Centre of Excellence in Biomedical Tuberculosis Research, US/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
| | - Nicolaas Claudius Gey van Pittius
- DST/NRF Centre of Excellence in Biomedical Tuberculosis Research, US/MRC Centre for Molecular and Cellular Biology, Division of Molecular Biology and Human Genetics, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
| | - Mae Newton-Foot
- Division of Medical Microbiology, Department of Pathology, Faculty of Medicine and Health Sciences, University of Stellenbosch, Francie van Zijl Drive, Tygerberg, 7505, South Africa.
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Identification of a lineage specific zinc responsive genomic island in Mycobacterium avium ssp. paratuberculosis. BMC Genomics 2014; 15:1076. [PMID: 25481572 PMCID: PMC4298942 DOI: 10.1186/1471-2164-15-1076] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 11/24/2014] [Indexed: 11/19/2022] Open
Abstract
Background Maintenance of metal homeostasis is crucial in bacterial pathogenicity as metal starvation is the most important mechanism in the nutritional immunity strategy of host cells. Thus, pathogenic bacteria have evolved sensitive metal scavenging systems to overcome this particular host defence mechanism. The ruminant pathogen Mycobacterium avium ssp. paratuberculosis (MAP) displays a unique gut tropism and causes a chronic progressive intestinal inflammation. MAP possesses eight conserved lineage specific large sequence polymorphisms (LSP), which distinguish MAP from its ancestral M. avium ssp. hominissuis or other M. avium subspecies. LSP14 and LSP15 harbour many genes proposed to be involved in metal homeostasis and have been suggested to substitute for a MAP specific, impaired mycobactin synthesis. Results In the present study, we found that a LSP14 located putative IrtAB-like iron transporter encoded by mptABC was induced by zinc but not by iron starvation. Heterologous reporter gene assays with the lacZ gene under control of the mptABC promoter in M. smegmatis (MSMEG) and in a MSMEG∆furB deletion mutant revealed a zinc dependent, metalloregulator FurB mediated expression of mptABC via a conserved mycobacterial FurB recognition site. Deep sequencing of RNA from MAP cultures treated with the zinc chelator TPEN revealed that 70 genes responded to zinc limitation. Remarkably, 45 of these genes were located on a large genomic island of approximately 90 kb which harboured LSP14 and LSP15. Thirty-five of these genes were predicted to be controlled by FurB, due to the presence of putative binding sites. This clustering of zinc responsive genes was exclusively found in MAP and not in other mycobacteria. Conclusions Our data revealed a particular genomic signature for MAP given by a unique zinc specific locus, thereby suggesting an exceptional relevance of zinc for the metabolism of MAP. MAP seems to be well adapted to maintain zinc homeostasis which might contribute to the peculiarity of MAP pathogenicity. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1076) contains supplementary material, which is available to authorized users.
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Singh PR, Bajaj H, Benz R, Winterhalter M, Mahendran KR. Transport across the outer membrane porin of mycolic acid containing actinomycetales: Nocardia farcinica. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:654-61. [PMID: 25462168 DOI: 10.1016/j.bbamem.2014.11.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 11/11/2014] [Accepted: 11/17/2014] [Indexed: 12/11/2022]
Abstract
The role of the outer-membrane channel from a mycolic acid containing Gram-positive bacteria Nocardia farcinica, which forms a hydrophilic pathway across the cell wall, was characterized. Single channel electrophysiology measurements and liposome swelling assays revealed the permeation of hydrophilic solutes including sugars, amino acids and antibiotics. The cation selective N. farcinica channel exhibited strong interaction with the positively charged antibiotics; amikacin and kanamycin, and surprisingly also with the negatively charged ertapenem. Voltage dependent kinetics of amikacin and kanamycin interactions were studied to distinguish binding from translocation. Moreover, the importance of charged residues inside the channel was investigated using mutational studies that revealed rate limiting interactions during the permeation.
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Affiliation(s)
- Pratik Raj Singh
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany.
| | - Harsha Bajaj
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
| | - Roland Benz
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
| | - Mathias Winterhalter
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany
| | - Kozhinjampara R Mahendran
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759 Bremen, Germany.
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Siegrist MS, Steigedal M, Ahmad R, Mehra A, Dragset MS, Schuster BM, Philips JA, Carr SA, Rubin EJ. Mycobacterial Esx-3 requires multiple components for iron acquisition. mBio 2014; 5:e01073-14. [PMID: 24803520 PMCID: PMC4010830 DOI: 10.1128/mbio.01073-14] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 03/28/2014] [Indexed: 12/16/2022] Open
Abstract
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 ΔmycP3ms mutant, failed to export the native Esx-3 substrates EsxHms and EsxGms 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 EsxHms and EsxGms were sufficient for iron acquisition under our experimental conditions. The apparent separation of Esx-3 function in iron acquisition from robust EsxGms and EsxHms secretion in the ΔmycP3ms 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.
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Affiliation(s)
- M. Sloan Siegrist
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, USA
| | | | - Rushdy Ahmad
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - Alka Mehra
- Division of Infectious Diseases, Department of Medicine, New York University School of Medicine, New York, New York, USA
| | | | - Brian M. Schuster
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, USA
| | - Jennifer A. Philips
- Division of Infectious Diseases, Department of Medicine, New York University School of Medicine, New York, New York, USA
| | - Steven A. Carr
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - Eric J. Rubin
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, USA
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Self-poisoning of Mycobacterium tuberculosis by interrupting siderophore recycling. Proc Natl Acad Sci U S A 2014; 111:1945-50. [PMID: 24497493 DOI: 10.1073/pnas.1311402111] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Siderophores are small iron-binding molecules secreted by bacteria to scavenge iron. Mycobacterium tuberculosis (Mtb), the etiologic agent of tuberculosis, produces the siderophores mycobactin and carboxymycobactin. Complexes of the mycobacterial membrane proteins MmpS4 and MmpS5 with the transporters MmpL4 and MmpL5 are required for siderophore export and virulence in Mtb. Here we show that, surprisingly, mycobactin or carboxymycobactin did not rescue the low-iron growth defect of the export mutant but severely impaired growth. Exogenous siderophores were taken up by the export mutant, and siderophore-delivered iron was used, but the deferrated siderophores accumulated intracellularly, indicating a blockade of siderophore recycling. This hypothesis was confirmed by the observation that radiolabeled carboxymycobactin was taken up and secreted again by Mtb. Addition of iron salts to an Mtb siderophore biosynthesis mutant stimulated more growth in the presence of a limiting amount of siderophores than iron-loaded siderophores alone. Thus, recycling enables Mtb to acquire iron at lower metabolic cost because Mtb cannot use iron salts without siderophores. Exogenous siderophores were bactericidal for the export mutant in submicromolar quantities. High-resolution mass spectrometry revealed that endogenous carboxymycobactin also accumulated in the export mutant. Toxic siderophore accumulation is prevented by a drug that inhibits siderophore biosynthesis. Intracellular accumulation of siderophores was toxic despite the use of an alternative iron source such as hemin, suggesting an additional inhibitory mechanism independent of iron availability. This study indicates that targeting siderophore export/recycling would deliver a one-two punch to Mtb: restricting access to iron and causing toxic intracellular siderophore accumulation.
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Serafini A, Pisu D, Palù G, Rodriguez GM, Manganelli R. The ESX-3 secretion system is necessary for iron and zinc homeostasis in Mycobacterium tuberculosis. PLoS One 2013; 8:e78351. [PMID: 24155985 PMCID: PMC3796483 DOI: 10.1371/journal.pone.0078351] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 09/18/2013] [Indexed: 12/25/2022] Open
Abstract
ESX-3 is one of the five type VII secretion systems encoded by the Mycobacterium tuberculosis genome. We recently showed the essentiality of ESX-3 for M. tuberculosis viability and proposed its involvement in iron and zinc metabolism. In this study we confirmed the role of ESX-3 in iron uptake and its involvement in the adaptation to low zinc environment in M. tuberculosis. Moreover, we unveiled functional differences between the ESX-3 roles in M. tuberculosis and M. smegmatis showing that in the latter ESX-3 is only involved in the adaptation to iron and not to zinc restriction. Finally, we also showed that in M. tuberculosis this secretion system is essential for iron and zinc homeostasis not only in conditions in which the concentrations of these metals are limiting but also in metal sufficient conditions.
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Affiliation(s)
- Agnese Serafini
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Davide Pisu
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - Giorgio Palù
- Department of Molecular Medicine, University of Padova, Padova, Italy
| | - G. Marcela Rodriguez
- Public Health Research Institute - Rutgers, the State University of New Jersey, Newark, New Jersey, United States of America
| | - Riccardo Manganelli
- Department of Molecular Medicine, University of Padova, Padova, Italy
- * E-mail:
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Abstract
Copper resistance mechanisms are crucial for many pathogenic bacteria, including Mycobacterium tuberculosis, during infection because the innate immune system utilizes copper ions to kill bacterial intruders. Despite several studies detailing responses of mycobacteria to copper, the pathways by which copper ions cross the mycobacterial cell envelope are unknown. Deletion of porin genes in Mycobacterium smegmatis leads to a severe growth defect on trace copper medium but simultaneously increases tolerance for copper at elevated concentrations, indicating that porins mediate copper uptake across the outer membrane. Heterologous expression of the mycobacterial porin gene mspA reduced growth of M. tuberculosis in the presence of 2.5 μM copper by 40% and completely suppressed growth at 15 μM copper, while wild-type M. tuberculosis reached its normal cell density at that copper concentration. Moreover, the polyamine spermine, a known inhibitor of porin activity in Gram-negative bacteria, enhanced tolerance of M. tuberculosis for copper, suggesting that copper ions utilize endogenous outer membrane channel proteins of M. tuberculosis to gain access to interior cellular compartments. In summary, these findings highlight the outer membrane as the first barrier against copper ions and the role of porins in mediating copper uptake in M. smegmatis and M. tuberculosis.
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Sorokin VV, Skladnev DA, Volkov VV, Tereshchenko EY, Mulukin AL, Gal'chenko VF. The pathways of silver nanoparticles formation by Mycobacterium smegmatis. DOKLADY BIOLOGICAL SCIENCES : PROCEEDINGS OF THE ACADEMY OF SCIENCES OF THE USSR, BIOLOGICAL SCIENCES SECTIONS 2013; 452:325-328. [PMID: 24150658 DOI: 10.1134/s0012496613050153] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Indexed: 06/02/2023]
Affiliation(s)
- V V Sorokin
- Winogradsky Institute of Microbiology, Russian Academy of Sciences, Moscow, Russia
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Ji B, Zhang SD, Arnoux P, Rouy Z, Alberto F, Philippe N, Murat D, Zhang WJ, Rioux JB, Ginet N, Sabaty M, Mangenot S, Pradel N, Tian J, Yang J, Zhang L, Zhang W, Pan H, Henrissat B, Coutinho PM, Li Y, Xiao T, Médigue C, Barbe V, Pignol D, Talla E, Wu LF. Comparative genomic analysis provides insights into the evolution and niche adaptation of marine Magnetospira sp. QH-2 strain. Environ Microbiol 2013; 16:525-44. [PMID: 23841906 DOI: 10.1111/1462-2920.12180] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 05/17/2013] [Accepted: 06/02/2013] [Indexed: 11/30/2022]
Abstract
Magnetotactic bacteria (MTB) are capable of synthesizing intracellular organelles, the magnetosomes, that are membrane-bounded magnetite or greigite crystals arranged in chains. Although MTB are widely spread in various ecosystems, few axenic cultures are available, and only freshwater Magnetospirillum spp. have been genetically analysed. Here, we present the complete genome sequence of a marine magnetotactic spirillum, Magnetospira sp. QH-2. The high number of repeats and transposable elements account for the differences in QH-2 genome structure compared with other relatives. Gene cluster synteny and gene correlation analyses indicate that the insertion of the magnetosome island in the QH-2 genome occurred after divergence between freshwater and marine magnetospirilla. The presence of a sodium-quinone reductase, sodium transporters and other functional genes are evidence of the adaptive evolution of Magnetospira sp. QH-2 to the marine ecosystem. Genes well conserved among freshwater magnetospirilla for nitrogen fixation and assimilatory nitrate respiration are absent from the QH-2 genome. Unlike freshwater Magnetospirillum spp., marine Magnetospira sp. QH-2 neither has TonB and TonB-dependent receptors nor does it grow on trace amounts of iron. Taken together, our results show a distinct, adaptive evolution of Magnetospira sp. QH-2 to marine sediments in comparison with its closely related freshwater counterparts.
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Affiliation(s)
- Boyang Ji
- Laboratoire de Chimie Bactérienne, Aix-Marseille Université, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7283, F-13402, Marseille Cedex 20, France
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Wendel SO, Perera AS, Pfromm PH, Czermak P, Bossmann SH. Adaptation of Mycobacterium smegmatis to an Industrial Scale Medium and Isolation of the Mycobacterial PorinMspA. Open Microbiol J 2013; 7:92-8. [PMID: 23802026 PMCID: PMC3680987 DOI: 10.2174/1874285801307010092] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 03/13/2013] [Accepted: 03/15/2013] [Indexed: 11/22/2022] Open
Abstract
The adaptation of the organism to a simple and cost-effective growth medium is mandatory in developing a process for large scale production of the octamericporinMspA, which is isolated from Mycobacterium smegmatis. A fermentation optimization with the minimal nutrients required for growth has been performed. During the fermentation, the iron- and ammonium chloride concentrations in the medium were varied to determine their impact on the observed growth rates and cell mass yields. Common antibiotics to control contamination were eliminated in favor of copper sulfate to reduce costs. MspA has been successfully isolated from the harvested M. smegmatisusing aqueous nOPOE (n-octyloligooxyethylene) at 65°C. Because of the extraordinary stability of MspA, it is possible to denature and precipitate virtually all other proteins and contaminants by following this approach. To further purify the product, acetone is used for precipitation. Gel electrophoresis confirmed the presence and purity of MspA. A maximum of 840µg (via Bradford assay) of pure MspA per liter of the optimized simple growth medium has been obtained. This is a 40% increase with respect to the previously reported culture medium for MspA.
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Affiliation(s)
- Sebastian O Wendel
- University of Applied Sciences Giessen-Friedberg, Institute of Bioprocess Engineering and Pharmaceutical Technology, Wiesenstrasse 14, 35390 Giessen, Germany ; Kansas State University, Department of Chemistry, Manhattan, 213 CBC Building, KS 66506-0401, USA ; Kansas State University, Department of Chemical Engineering, 1036 Durland Hall, Manhattan, KS 66506, USA
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Dissecting plant iron homeostasis under short and long-term iron fluctuations. Biotechnol Adv 2013; 31:1292-307. [PMID: 23680191 DOI: 10.1016/j.biotechadv.2013.05.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Revised: 04/18/2013] [Accepted: 05/05/2013] [Indexed: 12/30/2022]
Abstract
A wealth of information on the different aspects of iron homeostasis in plants has been obtained during the last decade. However, there is no clear road-map integrating the relationships between the various components. The principal aim of the current review is to fill this gap. In this context we discuss the lack of low affinity iron uptake mechanisms in plants, the utilization of a different uptake mechanism by graminaceous plants compared to the others, as well as the roles of riboflavin, ferritin isoforms, nitric oxide, nitrosylation, heme, aconitase, and vacuolar pH. Cross-homeostasis between elements is also considered, with a specific emphasis on the relationship between iron homeostasis and phosphorus and copper deficiencies. As the environment is a crucial parameter for modulating plant responses, we also highlight how diurnal fluctuations govern iron metabolism. Evolutionary aspects of iron homeostasis have so far attracted little attention. Looking into the past can inform us on how long-term oxygen and iron-availability fluctuations have influenced the evolution of iron uptake mechanisms. Finally, we evaluate to what extent this homeostastic road map can be used for the development of novel biofortification strategies in order to alleviate iron deficiency in human.
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Ruiz N. A bird's eye view of the bacterial landscape. Methods Mol Biol 2013; 966:1-14. [PMID: 23299725 DOI: 10.1007/978-1-62703-245-2_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Bacteria interact with the environment through their cell surface. Activities as diverse as attaching to a catheter, crawling on a surface, swimming through a pond, or being preyed on by a bacteriophage depend on the composition and structure of the cell surface. The cell surface must also protect bacteria from harmful chemicals present in the environment while allowing the intake of nutrients and excretion of toxic molecules. Bacteria have evolved four main types of bacterial cell surfaces to accomplish these functions: those of the typical gram-negative and gram-positive bacteria, and those of the Actinobacteria and Mollicutes. So few types seems remarkable since bacteria are very diverse and abundant, and they can live in many different environments. However, each species has tweaked these stereotypical bacterial surfaces to best fit its needs. The result is an amazing diversity of the bacterial landscape, most of which remains unexplored. Here I give an overview of the main features of the bacterial cell surface and highlight how advances in methodology have moved forward this field of study.
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Affiliation(s)
- Natividad Ruiz
- Department of Microbiology, The Ohio State University, Columbus, OH, USA.
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Wells RM, Jones CM, Xi Z, Speer A, Danilchanka O, Doornbos KS, Sun P, Wu F, Tian C, Niederweis M. Discovery of a siderophore export system essential for virulence of Mycobacterium tuberculosis. PLoS Pathog 2013; 9:e1003120. [PMID: 23431276 PMCID: PMC3561183 DOI: 10.1371/journal.ppat.1003120] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 11/24/2012] [Indexed: 11/18/2022] Open
Abstract
Iron is an essential nutrient for most bacterial pathogens, but is restricted by the host immune system. Mycobacterium tuberculosis (Mtb) utilizes two classes of small molecules, mycobactins and carboxymycobactins, to capture iron from the human host. Here, we show that an Mtb mutant lacking the mmpS4 and mmpS5 genes did not grow under low iron conditions. A cytoplasmic iron reporter indicated that the double mutant experienced iron starvation even under high-iron conditions. Loss of mmpS4 and mmpS5 did not change uptake of carboxymycobactin by Mtb. Thin layer chromatography showed that the ΔmmpS4/S5 mutant was strongly impaired in biosynthesis and secretion of siderophores. Pull-down experiments with purified proteins demonstrated that MmpS4 binds to a periplasmic loop of the associated transporter protein MmpL4. This interaction was corroborated by genetic experiments. While MmpS5 interacted only with MmpL5, MmpS4 interacted with both MmpL4 and MmpL5. These results identified MmpS4/MmpL4 and MmpS5/MmpL5 as siderophore export systems in Mtb and revealed that the MmpL proteins transport small molecules other than lipids. MmpS4 and MmpS5 resemble periplasmic adapter proteins of tripartite efflux pumps of Gram-negative bacteria, however, they are not only required for export but also for efficient siderophore synthesis. Membrane association of MbtG suggests a link between siderophore synthesis and transport. The structure of the soluble domain of MmpS4 (residues 52-140) was solved by NMR and indicates that mycobacterial MmpS proteins constitute a novel class of transport accessory proteins. The bacterial burden of the mmpS4/S5 deletion mutant in mouse lungs was lower by 10,000-fold and none of the infected mice died within 180 days compared to wild-type Mtb. This is the strongest attenuation observed so far for Mtb mutants lacking genes involved in iron utilization. In conclusion, this study identified the first components of novel siderophore export systems which are essential for virulence of Mtb.
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Affiliation(s)
- Ryan M. Wells
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Christopher M. Jones
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Zhaoyong Xi
- School of Chemistry and Material Sciences, University of Science and Technology of China, Hefei, P. R. China
| | - Alexander Speer
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Olga Danilchanka
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Kathryn S. Doornbos
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Peibei Sun
- School of Life Sciences, University of Science and Technology of China, Hefei, P. R. China
| | - Fangming Wu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, P. R. China
| | - Changlin Tian
- School of Life Sciences, University of Science and Technology of China, Hefei, P. R. China
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, P. R. China
| | - Michael Niederweis
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
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Bacillus cereus iron uptake protein fishes out an unstable ferric citrate trimer. Proc Natl Acad Sci U S A 2012; 109:16829-34. [PMID: 23027976 DOI: 10.1073/pnas.1210131109] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Citrate is a common biomolecule that chelates Fe(III). Many bacteria and plants use ferric citrate to fulfill their nutritional requirement for iron. Only the Escherichia coli ferric citrate outer-membrane transport protein FecA has been characterized; little is known about other ferric citrate-binding proteins. Here we report a unique siderophore-binding protein from the gram-positive pathogenic bacterium Bacillus cereus that binds multinuclear ferric citrate complexes. We have demonstrated that B. cereus ATCC 14579 takes up (55)Fe radiolabeled ferric citrate and that a protein, BC_3466 [renamed FctC (ferric citrate-binding protein C)], binds ferric citrate. The dissociation constant (K(d)) of FctC at pH 7.4 with ferric citrate (molar ratio 1:50) is 2.6 nM. This is the tightest binding observed of any B. cereus siderophore-binding protein. Nano electrospray ionization-mass spectrometry (nano ESI-MS) analysis of FctC and ferric citrate complexes or citrate alone show that FctC binds diferric di-citrate, and triferric tricitrate, but does not bind ferric di-citrate, ferric monocitrate, or citrate alone. Significantly, the protein selectively binds triferric tricitrate even though this species is naturally present at very low equilibrium concentrations.
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Characteristics of the freshwater cyanobacterium Microcystis aeruginosa grown in iron-limited continuous culture. Appl Environ Microbiol 2011; 78:1574-83. [PMID: 22210212 DOI: 10.1128/aem.06908-11] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A continuous culturing system (chemostat) made of metal-free materials was successfully developed and used to maintain Fe-limited cultures of Microcystis aeruginosa PCC7806 at nanomolar iron (Fe) concentrations (20 to 50 nM total Fe). EDTA was used to maintain Fe in solution, with bioavailable Fe controlled by absorption of light by the ferric EDTA complex and resultant reduction of Fe(III) to Fe(II). A kinetic model describing Fe transformations and biological uptake was applied to determine the biologically available form of Fe (i.e., unchelated ferrous iron) that is produced by photoreductive dissociation of the ferric EDTA complex. Prediction by chemostat theory modified to account for the light-mediated formation of bioavailable Fe rather than total Fe was in good agreement with growth characteristics of M. aeruginosa under Fe limitation. The cellular Fe quota increased with increasing dilution rates in a manner consistent with the Droop theory. Short-term Fe uptake assays using cells maintained at steady state indicated that M. aeruginosa cells vary their maximum Fe uptake rate (ρ(max)) depending on the degree of Fe stress. The rate of Fe uptake was lower for cells grown under conditions of lower Fe availability (i.e., lower dilution rate), suggesting that cells in the continuous cultures adjusted to Fe limitation by decreasing ρ(max) while maintaining a constant affinity for Fe.
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46
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Uptake of sulfate but not phosphate by Mycobacterium tuberculosis is slower than that for Mycobacterium smegmatis. J Bacteriol 2011; 194:956-64. [PMID: 22194452 DOI: 10.1128/jb.06132-11] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Knowledge of the metabolic pathways used by Mycobacterium tuberculosis during infection is important for understanding its nutrient requirements and host adaptation. However, uptake, the first step in the utilization of nutrients, is poorly understood for many essential nutrients, such as inorganic anions. Here, we show that M. tuberculosis utilizes nitrate as the sole nitrogen source, albeit at lower efficiency than asparagine, glutamate, and arginine. The growth of the porin triple mutant M. smegmatis ML16 in media with limiting amounts of nitrate and sulfate as sole nitrogen and sulfur sources, respectively, was delayed compared to that of the wild-type strain. The uptake of sulfate was 40-fold slower than that of the wild-type strain, indicating that the efficient uptake of these anions is dependent on porins. The uptake by M. tuberculosis of sulfate and phosphate was approximately 40- and 10-fold slower than that of M. smegmatis, respectively, which is consistent with the slower growth of M. tuberculosis. However, the uptake of these anions by M. tuberculosis is orders of magnitude faster than diffusion through lipid membranes, indicating that unknown outer membrane proteins are required to facilitate this process.
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47
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Mi X, He F, Xiang M, Lian Y, Yi S. Novel Phage Amplified Multichannel Series Piezoelectric Quartz Crystal Sensor for Rapid and Sensitive Detection of Mycobacterium tuberculosis. Anal Chem 2011; 84:939-46. [DOI: 10.1021/ac2020728] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xianwen Mi
- State Key Laboratory of Chemo/Biosensing
and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, China, 410082
- Huaihua Medical College, Huaihua, Hunan Province, China, 418000
| | - Fengjiao He
- State Key Laboratory of Chemo/Biosensing
and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, China, 410082
| | - Meiyu Xiang
- State Key Laboratory of Chemo/Biosensing
and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, China, 410082
| | - Yan Lian
- State Key Laboratory of Chemo/Biosensing
and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, China, 410082
| | - Songlin Yi
- Hunan Institute of Tuberculosis Control, Changsha, China, 410006
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Song H, Huff J, Janik K, Walter K, Keller C, Ehlers S, Bossmann SH, Niederweis M. Expression of the ompATb operon accelerates ammonia secretion and adaptation of Mycobacterium tuberculosis to acidic environments. Mol Microbiol 2011; 80:900-18. [PMID: 21410778 DOI: 10.1111/j.1365-2958.2011.07619.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Homeostasis of intracellular pH is a trait critical for survival of Mycobacterium tuberculosis in macrophages. However, mechanisms by which M. tuberculosis adapts to acidic environments are poorly understood. In this study, we analysed the physiological functions of OmpATb, a surface-accessible protein of M. tuberculosis. OmpATb did not complement the permeability defects of a Mycobacterium smegmatis porin mutant to glucose, serine and glycerol, in contrast to the porin MspA. Uptake rates of these solutes were unchanged in an ompATb operon mutant of M. tuberculosis indicating that OmpATb is not a general porin. Chemical analysis of low-pH culture filtrates showed that the proteins encoded by the ompATb operon are involved in generating a rapid ammonia burst, which neutralized medium pH and preceded exponential growth of M. tuberculosis. Addition of ammonia accelerated growth of the ompATb operon mutant demonstrating that ammonia secretion is indeed a mechanism by which M. tuberculosis neutralizes acidic environments. Infection experiments revealed that the ompATb operon was not required for full virulence in mice suggesting that M. tuberculosis has multiple mechanisms of resisting phagosomal acidification. Taken together, these results show that the ompATb operon is necessary for rapid ammonia secretion and adaptation of M. tuberculosis to acidic environments in vitro but not in mice.
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Affiliation(s)
- Houhui Song
- Department of Microbiology, University of Alabama at Birmingham, 609 Bevill Biomedical Research Building, 845 19th Street South, Birmingham, AL 35294, USA
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Dufourny L, Caraty A, Clarke IJ, Robinson JE, Skinner DC. Progesterone-receptive dopaminergic and neuropeptide Y neurons project from the arcuate nucleus to gonadotropin-releasing hormone-rich regions of the ovine preoptic area. Neuroendocrinology 2005; 82:21-31. [PMID: 16330883 DOI: 10.1159/000090122] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Accepted: 09/29/2005] [Indexed: 11/19/2022]
Abstract
Progesterone inhibits gonadotropin-releasing hormone (GnRH) secretion in sheep through an interneuronal system located in the mediobasal hypothalamus. This study focused on known inhibitors of GnRH secretion in sheep, dopamine and neuropeptide Y (NPY). As the distributions of tyrosine hydroxylase (TH)- and NPY-immunoreactive neurons overlap with progesterone receptors (PR) in the arcuate nucleus, we hypothesized that, if these neurons mediate, at least partially, the inhibitory feedback signal of progesterone, then they should co-express PRs. Fluorogold (FG), a retrograde tracer, was injected into the preoptic area of ovariectomized ewes pretreated with estrogen and progesterone. When the FG injection site encompassed at least 80 GnRH neurons, sections from the arcuate nucleus were processed using dual immunocytochemistry for PR and either TH or NPY. We found that 30% of PR-immunoreactive, 12% of TH-containing and 21% of NPY-synthesizing neurons project toward this GnRH-rich region. Of the PR/TH dual-labeled cells, which represent 21% of PR and 31% of TH cells, respectively, 22% displayed FG labeling. Of the PR/NPY neurons, which account for 19% of PR and 67% of NPY neurons, respectively, 26% were FG fluorescent. This study suggests that subsets of arcuate nucleus dopaminergic and NPY neurons may transduce, at least in part, the progesterone-mediated inhibition of GnRH secretion.
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Affiliation(s)
- Laurence Dufourny
- Department of Zoology & Physiology, University of Wyoming, Laramie, WY 82071, USA
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