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Espejo LS, DeNicola D, Chang LM, Hofschneider V, Haskins AE, Balsa J, Freitas SS, Antenor A, Hamming S, Hull B, Castro-Portuguez R, Dang H, Sutphin GL. The Emerging Role of 3-Hydroxyanthranilic Acid on C. elegans Aging Immune Function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.07.574394. [PMID: 38260592 PMCID: PMC10802494 DOI: 10.1101/2024.01.07.574394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
3-hydroxyanthranilic acid (3HAA) is considered to be a fleeting metabolic intermediate along tryptophan catabolism through the kynurenine pathway. 3HAA and the rest of the kynurenine pathway have been linked to immune response in mammals yet whether it is detrimental or advantageous is a point of contention. Recently we have shown that accumulation of this metabolite, either through supplementation or prevention of its degradation, extends healthy lifespan in C. elegans and mice, while the mechanism remained unknown. Utilizing C. elegans as a model we investigate how 3HAA and haao-1 inhibition impact the host and the potential pathogens. What we find is that 3HAA improves host immune function with aging and serves as an antimicrobial against gram-negative bacteria. Regulation of 3HAA's antimicrobial activity is accomplished via tissue separation. 3HAA is synthesized in the C. elegans hypodermal tissue, localized to the site of pathogen interaction within the gut granules, and degraded in the neuronal cells. This tissue separation creates a new possible function for 3HAA that may give insight to a larger evolutionarily conserved function within the immune response.
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Affiliation(s)
- Luis S Espejo
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Destiny DeNicola
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Leah M Chang
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | | | - Anne E Haskins
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Jonah Balsa
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Samuel S Freitas
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Angelo Antenor
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Sage Hamming
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Bradford Hull
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | | | - Hope Dang
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - George L Sutphin
- Molecular & Cellular Biology, University of Arizona, Tucson, AZ, USA
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2
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Pijuan J, Moreno DF, Yahya G, Moisa M, Ul Haq I, Krukiewicz K, Mosbah R, Metwally K, Cavalu S. Regulatory and pathogenic mechanisms in response to iron deficiency and excess in fungi. Microb Biotechnol 2023; 16:2053-2071. [PMID: 37804207 PMCID: PMC10616654 DOI: 10.1111/1751-7915.14346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 09/14/2023] [Accepted: 09/19/2023] [Indexed: 10/09/2023] Open
Abstract
Iron is an essential element for all eukaryote organisms because of its redox properties, which are important for many biological processes such as DNA synthesis, mitochondrial respiration, oxygen transport, lipid, and carbon metabolism. For this reason, living organisms have developed different strategies and mechanisms to optimally regulate iron acquisition, transport, storage, and uptake in different environmental responses. Moreover, iron plays an essential role during microbial infections. Saccharomyces cerevisiae has been of key importance for decrypting iron homeostasis and regulation mechanisms in eukaryotes. Specifically, the transcription factors Aft1/Aft2 and Yap5 regulate the expression of genes to control iron metabolism in response to its deficiency or excess, adapting to the cell's iron requirements and its availability in the environment. We also review which iron-related virulence factors have the most common fungal human pathogens (Aspergillus fumigatus, Cryptococcus neoformans, and Candida albicans). These factors are essential for adaptation in different host niches during pathogenesis, including different fungal-specific iron-uptake mechanisms. While being necessary for virulence, they provide hope for developing novel antifungal treatments, which are currently scarce and usually toxic for patients. In this review, we provide a compilation of the current knowledge about the metabolic response to iron deficiency and excess in fungi.
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Affiliation(s)
- Jordi Pijuan
- Laboratory of Neurogenetics and Molecular MedicineInstitut de Recerca Sant Joan de DéuBarcelonaSpain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), ISCIIIMadridSpain
| | - David F. Moreno
- Department of Molecular Cellular and Developmental BiologyYale UniversityNew HavenConnecticutUSA
- Systems Biology InstituteYale UniversityWest HavenConnecticutUSA
- Institut de Génétique et de Biologie Moléculaire et CellulaireIllkirchFrance
| | - Galal Yahya
- Department of Microbiology and Immunology, Faculty of PharmacyZagazig UniversityAl SharqiaEgypt
| | - Mihaela Moisa
- Faculty of Medicine and PharmacyUniversity of OradeaOradeaRomania
| | - Ihtisham Ul Haq
- Department of Physical Chemistry and Polymers TechnologySilesian University of TechnologyGliwicePoland
- Programa de Pós‐graduação em Inovação TecnológicaUniversidade Federal de Minas GeraisBelo HorizonteBrazil
| | - Katarzyna Krukiewicz
- Department of Physical Chemistry and Polymers TechnologySilesian University of TechnologyGliwicePoland
- Centre for Organic and Nanohybrid ElectronicsSilesian University of TechnologyGliwicePoland
| | - Rasha Mosbah
- Infection Control UnitHospitals of Zagazig UniversityZagazigEgypt
| | - Kamel Metwally
- Department of Medicinal Chemistry, Faculty of PharmacyUniversity of TabukTabukSaudi Arabia
- Department of Pharmaceutical Medicinal Chemistry, Faculty of PharmacyZagazig UniversityZagazigEgypt
| | - Simona Cavalu
- Faculty of Medicine and PharmacyUniversity of OradeaOradeaRomania
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Moreira-Walsh B, Ragsdale A, Lam W, Upadhya R, Xu E, Lodge JK, Donlin MJ. Membrane Integrity Contributes to Resistance of Cryptococcus neoformans to the Cell Wall Inhibitor Caspofungin. mSphere 2022; 7:e0013422. [PMID: 35758672 PMCID: PMC9429927 DOI: 10.1128/msphere.00134-22] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 06/01/2022] [Indexed: 01/20/2023] Open
Abstract
The fungal pathogen Cryptococcus neoformans causes up to 278 000 infections each year globally, resulting in up to 180,000 deaths annually, mostly impacting immunocompromised people. Therapeutic options for C. neoformans infections are very limited. Caspofungin, a member of the echinocandin class of antifungals, is generally well tolerated but clinically ineffective against C. neoformans. We sought to identify biological processes that can be targeted to render the cell more susceptible to echinocandins by screening the available libraries of gene deletion mutants made in the KN99α background for caspofungin sensitivity. We adapted a Candida albicans fungal biofilm assay for the growth characteristics of C. neoformans and systematically screened 4,030 individual gene deletion mutants in triplicate plate assays. We identified 25 strains that showed caspofungin sensitivity. We followed up with a dose dependence assay, and 17 of the 25 were confirmed sensitive, 5 of which were also sensitive in an agar plate assay. We made new deletion mutant strains for four of these genes: CFT1, encoding an iron transporter; ERG4, encoding a sterol desaturase; MYO1, encoding a myosin heavy chain; and YSP2, encoding a sterol transporter. All were more sensitive to membrane stress and showed significantly increased sensitivity to caspofungin at higher temperatures. Surprisingly, none showed any obvious cell wall defects such as would be expected for caspofungin-sensitive strains. Our microscopy analyses suggested that loss of membrane integrity contributed to the caspofungin sensitivity, either by allowing more caspofungin to enter or remain in the cell or by altering the location or orientation of the enzyme target to render it more susceptible to inhibition. IMPORTANCE The intrinsic resistance of Cryptococcus neoformans to the cell wall inhibitor caspofungin limits the available therapies for treating cryptococcal infections. We screened a collection of more than 4,000 gene deletion strains for altered caspofungin sensitivity to identify biological processes that could be targeted to render the cell more susceptible to caspofungin. We identified multiple genes with an effect on caspofungin susceptibility and found that they were associated with altered membrane permeability rather than the expected cell wall defects. This suggests that targeting these genes or other genes affecting membrane permeability is a viable path for developing novel therapies for treating this global fungal pathogen.
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Affiliation(s)
- Brenda Moreira-Walsh
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
| | - Abigail Ragsdale
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Woei Lam
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Rajendra Upadhya
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Evan Xu
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
| | - Jennifer K. Lodge
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Maureen J. Donlin
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
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Song M, Thak EJ, Kang HA, Kronstad JW, Jung WH. Cryptococcus neoformans can utilize ferritin as an iron source. Med Mycol 2022; 60:myac056. [PMID: 35943215 PMCID: PMC9387142 DOI: 10.1093/mmy/myac056] [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: 05/03/2022] [Revised: 07/11/2022] [Accepted: 08/06/2022] [Indexed: 01/21/2023] Open
Abstract
UNLABELLED Ferritin, a major iron storage protein in vertebrates, supplies iron upon iron deficiency. Ferritin is also found extracellularly, and acts as an iron carrier and a contributor to the immune response to invading microbes. Some microbial pathogens take advantage of ferritin as an iron source upon infection. However, no information is currently available on whether the human fungal pathogen Cryptococcus neoformans can acquire iron from ferritin. Here, we found that C. neoformans grew well in the presence of ferritin as a sole iron source. We showed that the binding of ferritin to the surface of C. neoformans is necessary and that acidification may contribute to ferritin-iron utilization by the fungus. Our data also revealed that the high-affinity reductive iron uptake system in C. neoformans is required for ferritin-iron acquisition. Furthermore, phagocytosis of C. neoformans by macrophages led to increased intracellular ferritin levels, suggesting that iron is sequestered by ferritin in infected macrophages. The increase in intracellular ferritin levels was reversed upon infection with a C. neoformans mutant deficient in the high-affinity reductive iron uptake system, indicating that this system plays a major role in iron acquisition in the phagocytosed C. neoformans in macrophages. LAY SUMMARY Cryptococcus neoformans is an opportunistic fungal pathogen causing life-threatening pulmonary disease and cryptococcal meningitis, mainly in immunocompromised patients. In this study, we found that C. neoformans can use ferritin, a major iron storage protein in vertebrates, as a sole iron source.
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Affiliation(s)
- Moonyong Song
- Department of Systems Biotechnology, Chung-Ang University, Anseong 17546, Korea
| | - Eun Jung Thak
- Department of Life Science, Chung-Ang University, Seoul 06974, Korea
| | - Hyun Ah Kang
- Department of Life Science, Chung-Ang University, Seoul 06974, Korea
| | - James W Kronstad
- Michael Smith Laboratories, Department of Microbiology & Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Won Hee Jung
- Department of Systems Biotechnology, Chung-Ang University, Anseong 17546, Korea
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Abstract
In an oxygenic environment, poorly soluble Fe3+ must be reduced to meet the cellular Fe2+ demand. This study demonstrates that elevated CO2/HCO3− levels accelerate chemical Fe3+ reduction through phenolic compounds, thus increasing intracellular Fe2+ availability. A number of biological environments are characterized by the presence of phenolic compounds and elevated HCO3− levels and include soil habitats and the human body. Fe2+ availability is of particular interest in the latter, as it controls the infectiousness of pathogens. Since the effect postulated here is abiotic, it generally affects the Fe2+ distribution in nature. Iron is a vital mineral for almost all living organisms and has a pivotal role in central metabolism. Despite its great abundance on earth, the accessibility for microorganisms is often limited, because poorly soluble ferric iron (Fe3+) is the predominant oxidation state in an aerobic environment. Hence, the reduction of Fe3+ is of essential importance to meet the cellular demand of ferrous iron (Fe2+) but might become detrimental as excessive amounts of intracellular Fe2+ tend to undergo the cytotoxic Fenton reaction in the presence of hydrogen peroxide. We demonstrate that the complex formation rate of Fe3+ and phenolic compounds like protocatechuic acid was increased by 46% in the presence of HCO3− and thus accelerated the subsequent redox reaction, yielding reduced Fe2+. Consequently, elevated CO2/HCO3− levels increased the intracellular Fe2+ availability, which resulted in at least 50% higher biomass-specific fluorescence of a DtxR-based Corynebacterium glutamicum reporter strain, and stimulated growth. Since the increased Fe2+ availability was attributed to the interaction of HCO3− and chemical iron reduction, the abiotic effect postulated in this study is of general relevance in geochemical and biological environments.
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Santana CS, Nicodemos Ramos MD, Vieira Velloso CC, Aguiar A. Kinetic Evaluation of Dye Decolorization by Fenton Processes in the Presence of 3-Hydroxyanthranilic Acid. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2019; 16:ijerph16091602. [PMID: 31067822 PMCID: PMC6540061 DOI: 10.3390/ijerph16091602] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 04/30/2019] [Accepted: 05/02/2019] [Indexed: 11/16/2022]
Abstract
The fungal metabolite 3-hydroxyanthranilic acid (3-HAA) was used as a redox mediatorwith the aim of increasing dye degradation by Fenton oxidative processes (Fe2+/H2O2, Fe3+/H2O2). ItsFe3+-reducing activity can enhance the generation of reactive oxygen species as HO● radicals.Initially, the influence of 3-HAA on decolorization kinetics of five dyes (methylene blue,chromotrope 2R, methyl orange, phenol red, and safranin T) was investigated using decolorizationdata from a previous work conducted by the present research group. Fe3+-containing reaction datawere well fitted with first-order and mainly second-order kinetic models, whereas the BMG(Behnajady, Modirshahla and Ghanbary) model obtained optimal fit to Fe2+. Improvements inkinetic parameters (i.e., apparent rate constants and maximum oxidation capacity) were observedwith the addition of 3-HAA. In another set of experiments, a decrease in apparent activation energywas observed due to introducing 3-HAA into reactions containing either Fe2+ or Fe3+ in order todecolorize phenol red at different temperatures. This indicates that the redox mediator decreasesthe energy barrier so as to allow reactions to occur. Thus, based on recent experiments and thereaction kinetics models evaluated herein, pro-oxidant properties have been observed for 3-HAAin Fenton processes.
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Affiliation(s)
- Cássia Sidney Santana
- Campus Alto Paraopeba, Universidade Federal de São João Del-Rei, Ouro Branco-MG 36420-000, Brazil.
| | | | | | - André Aguiar
- Instituto de Recursos Naturais, Universidade Federal de Itajubá, Itajubá-MG 37500-903, Brazil.
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The Role of Copper Homeostasis at the Host-Pathogen Axis: From Bacteria to Fungi. Int J Mol Sci 2019; 20:ijms20010175. [PMID: 30621285 PMCID: PMC6337107 DOI: 10.3390/ijms20010175] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 12/28/2018] [Accepted: 12/29/2018] [Indexed: 02/01/2023] Open
Abstract
Copper is an essential trace element participating in many vital biological processes, however it becomes a toxic agent when in excess. Thus, precise and tight regulation of copper homeostasis processes, including transport, delivery, storage, detoxification, and efflux machineries, is important, ensuring that only the amount needed to sustain basic biological functions and simultaneously prevent copper toxicity in the cell is maintained. Numerous exciting studies have revealed that copper plays an indispensable role at the microbial pathogen-host axis for entities ranging from pathogenic bacteria to deadly fungal species. Analyses of copper homeostases in bacteria and fungi extensively demonstrate that copper is utilized by the host immune system as an anti-microbial agent. The expression of copper efflux and detoxification from microbial pathogens is induced to counteract the host's copper bombardment, which in turn disrupts these machineries, resulting in the attenuation of microbial survival in host tissue. We hereby review the latest work in copper homeostases in pathogenic bacteria and fungi and focus on the maintenance of a copper balance at the pathogen-host interaction axis.
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8
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Gerwien F, Skrahina V, Kasper L, Hube B, Brunke S. Metals in fungal virulence. FEMS Microbiol Rev 2018; 42:4562650. [PMID: 29069482 PMCID: PMC5812535 DOI: 10.1093/femsre/fux050] [Citation(s) in RCA: 143] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 10/19/2017] [Indexed: 12/25/2022] Open
Abstract
Metals are essential for life, and they play a central role in the struggle between infecting microbes and their hosts. In fact, an important aspect of microbial pathogenesis is the 'nutritional immunity', in which metals are actively restricted (or, in an extended definition of the term, locally enriched) by the host to hinder microbial growth and virulence. Consequently, fungi have evolved often complex regulatory networks, uptake and detoxification systems for essential metals such as iron, zinc, copper, nickel and manganese. These systems often differ fundamentally from their bacterial counterparts, but even within the fungal pathogens we can find common and unique solutions to maintain metal homeostasis. Thus, we here compare the common and species-specific mechanisms used for different metals among different fungal species-focusing on important human pathogens such as Candida albicans, Aspergillus fumigatus or Cryptococcus neoformans, but also looking at model fungi such as Saccharomyces cerevisiae or A. nidulans as well-studied examples for the underlying principles. These direct comparisons of our current knowledge reveal that we have a good understanding how model fungal pathogens take up iron or zinc, but that much is still to learn about other metals and specific adaptations of individual species-not the least to exploit this knowledge for new antifungal strategies.
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Affiliation(s)
- Franziska Gerwien
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
| | - Volha Skrahina
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
| | - Lydia Kasper
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
| | - Bernhard Hube
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
| | - Sascha Brunke
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology– Hans Knoell Institute, 07745 Jena, Germany
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Suo CH, Ma LJ, Li HL, Sun JF, Li C, Lin MH, Sun TS, Du W, Li YJ, Gao XD, Meng Y, Sai SX, Ding C. Investigation of Cryptococcus neoformans magnesium transporters reveals important role of vacuolar magnesium transporter in regulating fungal virulence factors. Microbiologyopen 2017; 7:e00564. [PMID: 29243387 PMCID: PMC6011977 DOI: 10.1002/mbo3.564] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 10/30/2017] [Indexed: 01/21/2023] Open
Abstract
Cryptococcus neoformans is an important opportunistic fungal pathogen in humans. Recent studies have demonstrated that metals are critical factors for the regulation of fungal virulence in hosts. In this study, we systemically investigated the function of C. neoformans magnesium transporters in controlling the intracellular Mg balance and virulence-associated factors. We identified three Mg transporters in C. neoformans: Mgt1, Mgt2, and Mgt3. While we could not detect a Mg2+ -related growth phenotype in mgt1 and mgt3 knockout strains, a GAL7p-Mgt2 strain showed significant Mg-dependent growth defects in the presence of glucose. Further analysis demonstrated that MGT2 is a homolog of MNR2 in Saccharomyces cerevisiae, which is localized to the vacuolar membrane and participates in intracellular Mg transport. Interestingly, a transcriptome analysis showed that Mgt2 influenced the expression of 19 genes, which were independent of Mg2+ . We showed that melanin synthesis in C. neoformans required Mg2+ and Mgt2, and that capsule production was negatively regulated by Mg2+ and Mgt2. Repressing the expression of MGT2-induced capsule, which resulted in an increased fungal burden in the lungs. Cumulatively, this study sets the stage for further evaluation of the important role of Mg homeostasis in the regulation of melanin and capsule in C. neoformans.
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Affiliation(s)
- Chen-Hao Suo
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Lan-Jing Ma
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Hai-Long Li
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Jian-Fang Sun
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Chao Li
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Ming-Hui Lin
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Tian-Shu Sun
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Wei Du
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Yan-Jian Li
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Xin-Di Gao
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Yang Meng
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
| | - Si-Xiang Sai
- School of Medicine, Binzhou Medical University, Yantai, Shandong, China
| | - Chen Ding
- College of Life and Health Sciences, Northeastern University, Liaoning, Shenyang, China
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10
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Rehman L, Su X, Li X, Qi X, Guo H, Cheng H. FreB is involved in the ferric metabolism and multiple pathogenicity-related traits of Verticillium dahliae. Curr Genet 2017; 64:645-659. [PMID: 29177887 DOI: 10.1007/s00294-017-0780-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Revised: 10/25/2017] [Accepted: 11/08/2017] [Indexed: 01/31/2023]
Abstract
Ferric reductases are integral membrane proteins involved in the reduction of environmental ferric iron into the biologically available ferrous iron. In the most overwhelming phytopathogenic fungus, Verticillium dahliae, these ferric reductase are not studied in details. In this study we explored the role of FreB gene (VDAG_06616) in the ferric reduction and virulence of V. dahliae by generating the knockout mutants (ΔFreB) and complementary strains (ΔFreB-C) using protoplast transformation. When cultured on media supplemented with FeSO4, FeCl3 and no iron, ΔFreB exhibited significantly reduced growth and spore production especially on media with no iron. Transmembrane ferric reductase activity of ΔFreB was decreased up to 50% than wild type strains (Vd-wt). The activity was fully restored in ΔFreB-C. Meanwhile, the expression levels of other related genes (Frect-4, Frect-5, Frect-6 and Met) were obviously increased in ΔFreB. Compared with the Vd-wt and ΔFreB-C, ΔFreB-1 and ΔFreB-2 were impaired in colony diameter and spore number on different carbon sources (starch, sucrose, galactose and xylose). ΔFreB-1 and ΔFreB-2 were also highly sensitive to oxidative stress as revealed by the plate diffusion assay when 100 µM H2O2 was applied to the fungal culture. When Nicotiana benthamiana plants were inoculated, ΔFreB exhibited less disease symptoms than Vd-wt and ΔFreB-C. In conclusion, the present findings not only indicate that FreB mediates the ferric metabolism and is required for the full virulence in V. dahliae, but would also accelerate future investigation to uncover the pathogenic mechanism of this fungus.
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Affiliation(s)
- Latifur Rehman
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Xiaofeng Su
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Xiaokang Li
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Xiliang Qi
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Huiming Guo
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China
| | - Hongmei Cheng
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
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11
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Nutritional Requirements and Their Importance for Virulence of Pathogenic Cryptococcus Species. Microorganisms 2017; 5:microorganisms5040065. [PMID: 28974017 PMCID: PMC5748574 DOI: 10.3390/microorganisms5040065] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 09/27/2017] [Accepted: 09/27/2017] [Indexed: 12/12/2022] Open
Abstract
Cryptococcus sp. are basidiomycete yeasts which can be found widely, free-living in the environment. Interactions with natural predators, such as amoebae in the soil, are thought to have promoted the development of adaptations enabling the organism to survive inside human macrophages. Infection with Cryptococcus in humans occurs following inhalation of desiccated yeast cells or spore particles and may result in fatal meningoencephalitis. Human disease is caused almost exclusively by the Cryptococcus neoformans species complex, which predominantly infects immunocompromised patients, and the Cryptococcus gattii species complex, which is capable of infecting immunocompetent individuals. The nutritional requirements of Cryptococcus are critical for its virulence in animals. Cryptococcus has evolved a broad range of nutrient acquisition strategies, many if not most of which also appear to contribute to its virulence, enabling infection of animal hosts. In this review, we summarise the current understanding of nutritional requirements and acquisition in Cryptococcus and offer perspectives to its evolution as a significant pathogen of humans.
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12
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Gerwien F, Safyan A, Wisgott S, Brunke S, Kasper L, Hube B. The Fungal Pathogen Candida glabrata Does Not Depend on Surface Ferric Reductases for Iron Acquisition. Front Microbiol 2017. [PMID: 28642757 PMCID: PMC5463049 DOI: 10.3389/fmicb.2017.01055] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Iron acquisition is a crucial virulence determinant for many bacteria and fungi, including the opportunistic fungal pathogens Candida albicans and C. glabrata. While the diverse strategies used by C. albicans for obtaining iron from the host are well-described, much less is known about the acquisition of this micronutrient from host sources by C. glabrata – a distant relative of C. albicans with closer evolutionary ties to Saccharomyces cerevisiae, which nonetheless causes severe clinical symptoms in humans. Here we show that C. glabrata is much more restricted than C. albicans in using host iron sources, lacking, for example, the ability to grow on transferrin and hemin/hemoglobin. Instead, C. glabrata is able to use ferritin and non-protein-bound iron (FeCl3) as iron sources in a pH-dependent manner. As in other fungal pathogens, iron-dependent growth requires the reductive high affinity (HA) iron uptake system. Typically highly conserved, this uptake mechanism normally relies on initial ferric reduction by cell-surface ferric reductases. The C. glabrata genome contains only three such putative ferric reductases, which were found to be dispensable for iron-dependent growth. In addition and in contrast to C. albicans and S. cerevisiae, we also detected no surface ferric reductase activity in C. glabrata. Instead, extracellular ferric reduction was found in this and the two other fungal species, which was largely dependent on an excreted low-molecular weight, non-protein ferric reductant. We therefore propose an iron acquisition strategy of C. glabrata which differs from other pathogenic fungi, such as C. albicans, in that it depends on a limited set of host iron sources and that it lacks the need for surface ferric reductases. Extracellular ferric reduction by a secreted molecule possibly compensates for the loss of surface ferric reductase activity in the HA iron uptake system.
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Affiliation(s)
- Franziska Gerwien
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Abu Safyan
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Stephanie Wisgott
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Sascha Brunke
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Lydia Kasper
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany
| | - Bernhard Hube
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell InstituteJena, Germany.,Department of Microbial Pathogenicity Mechanisms, Friedrich Schiller UniversityJena, Germany.,Center for Sepsis Control and Care, University HospitalJena, Germany
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13
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Rosenfeld CE, Kenyon JA, James BR, Santelli CM. Selenium (IV,VI) reduction and tolerance by fungi in an oxic environment. GEOBIOLOGY 2017; 15:441-452. [PMID: 28044397 DOI: 10.1111/gbi.12224] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 12/07/2016] [Indexed: 05/27/2023]
Abstract
Microbial processes are known to mediate selenium (Se) oxidation-reduction reactions, strongly influencing Se speciation, bioavailability, and transport throughout the environment. While these processes have commonly been studied in anaerobic bacteria, the role that aerobic fungi play in Se redox reactions could be important for Se-rich soil systems, dominated by microbial activity. We quantified fungal growth, aerobic Se(IV, VI) reduction, and Se immobilization and volatilization in the presence of six, metal-tolerant Ascomycete fungi. We found that the removal of dissolved Se was dependent on the fungal species, Se form (i.e., selenite or selenate), and Se concentration. All six species grew and removed dissolved Se(IV) or Se(VI) from solution, with five species reducing both oxyanions to Se(0) biominerals, and all six species removing at least 15%-20% of the supplied Se via volatilization. Growth rates of all fungi, however, decreased with increasing Se(IV,VI) concentrations. All fungi removed 85%-93% of the dissolved Se(IV) within 10 d in the presence of 0.01 mm Se(IV), although only about 20%-30% Se(VI) was removed when grown with 0.01 mm Se(VI). Fungi-produced biominerals were typically 50- to 300-nm-diameter amorphous or paracrystalline spherical Se(0) nanoparticles. Our results demonstrate that activity of common soil fungi can influence Se form and distribution, and these organisms may therefore play a role in detoxifying Se-polluted environments.
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Affiliation(s)
- C E Rosenfeld
- Department of Mineral Sciences, Smithsonian Institution National Museum of Natural History, Washington, DC, USA
- Department of Earth Science and BioTechnology Institute, University of Minnesota - Twin Cities, Minneapolis, MN, USA
| | - J A Kenyon
- Department of Mineral Sciences, Smithsonian Institution National Museum of Natural History, Washington, DC, USA
- MIT/WHOI Joint Program in Oceanography, Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - B R James
- Department of Environmental Science and Technology, University of Maryland, College Park, MD, USA
| | - C M Santelli
- Department of Mineral Sciences, Smithsonian Institution National Museum of Natural History, Washington, DC, USA
- Department of Earth Science and BioTechnology Institute, University of Minnesota - Twin Cities, Minneapolis, MN, USA
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14
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The Zinc Finger Protein Mig1 Regulates Mitochondrial Function and Azole Drug Susceptibility in the Pathogenic Fungus Cryptococcus neoformans. mSphere 2016; 1:mSphere00080-15. [PMID: 27303693 PMCID: PMC4863601 DOI: 10.1128/msphere.00080-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 12/17/2015] [Indexed: 12/31/2022] Open
Abstract
Fungal pathogens of humans are difficult to treat, and there is a pressing need to identify new targets for antifungal drugs and to obtain a detailed understanding of fungal proliferation in vertebrate hosts. In this study, we examined the roles of the regulatory proteins Mig1 and HapX in mitochondrial function and antifungal drug susceptibility in the fungus Cryptococcus neoformans. This pathogen is a particular threat to the large population of individuals infected with human immunodeficiency virus (HIV). Our analysis revealed regulatory interactions between Mig1 and HapX, and a role for Mig1 in mitochondrial functions, including respiration, tolerance for reactive oxygen species, and expression of genes for iron consumption and iron acquisition functions. Importantly, loss of Mig1 increased susceptibility to the antifungal drug fluconazole, which is commonly used to treat cryptococcal disease. These studies highlight an association between mitochondrial dysfunction and drug susceptibility that may provide new targets for the development of antifungal drugs. The opportunistic pathogen Cryptococcus neoformans causes fungal meningoencephalitis in immunocompromised individuals. In previous studies, we found that the Hap complex in this pathogen represses genes encoding mitochondrial respiratory functions and tricarboxylic acid (TCA) cycle components under low-iron conditions. The orthologous Hap2/3/4/5 complex in Saccharomyces cerevisiae exerts a regulatory influence on mitochondrial functions, and Hap4 is subject to glucose repression via the carbon catabolite repressor Mig1. In this study, we explored the regulatory link between a candidate ortholog of the Mig1 protein and the HapX component of the Hap complex in C. neoformans. This analysis revealed repression of MIG1 by HapX and activation of HAPX by Mig1 under low-iron conditions and Mig1 regulation of mitochondrial functions, including respiration, tolerance for reactive oxygen species, and expression of genes for iron consumption and iron acquisition functions. Consistently with these regulatory functions, a mig1Δ mutant had impaired growth on inhibitors of mitochondrial respiration and inducers of ROS. Furthermore, deletion of MIG1 provoked a dysregulation in nutrient sensing via the TOR pathway and impacted the pathway for cell wall remodeling. Importantly, loss of Mig1 increased susceptibility to fluconazole, thus further establishing a link between azole antifungal drugs and mitochondrial function. Mig1 and HapX were also required together for survival in macrophages, but Mig1 alone had a minimal impact on virulence in mice. Overall, these studies provide novel insights into a HapX/Mig1 regulatory network and reinforce an association between mitochondrial dysfunction and drug susceptibility that may provide new targets for the development of antifungal drugs. IMPORTANCE Fungal pathogens of humans are difficult to treat, and there is a pressing need to identify new targets for antifungal drugs and to obtain a detailed understanding of fungal proliferation in vertebrate hosts. In this study, we examined the roles of the regulatory proteins Mig1 and HapX in mitochondrial function and antifungal drug susceptibility in the fungus Cryptococcus neoformans. This pathogen is a particular threat to the large population of individuals infected with human immunodeficiency virus (HIV). Our analysis revealed regulatory interactions between Mig1 and HapX, and a role for Mig1 in mitochondrial functions, including respiration, tolerance for reactive oxygen species, and expression of genes for iron consumption and iron acquisition functions. Importantly, loss of Mig1 increased susceptibility to the antifungal drug fluconazole, which is commonly used to treat cryptococcal disease. These studies highlight an association between mitochondrial dysfunction and drug susceptibility that may provide new targets for the development of antifungal drugs.
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15
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Aubi O, Flydal MI, Zheng H, Skjærven L, Rekand I, Leiros HKS, Haug BE, Cianciotto NP, Martinez A, Underhaug J. Discovery of a Specific Inhibitor of Pyomelanin Synthesis in Legionella pneumophila. J Med Chem 2015; 58:8402-12. [DOI: 10.1021/acs.jmedchem.5b01589] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Oscar Aubi
- Department
of Biomedicine, University of Bergen, Bergen, Norway
| | - Marte I. Flydal
- Department
of Biomedicine, University of Bergen, Bergen, Norway
| | - Huaixin Zheng
- Department
of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois 60611, United States
| | - Lars Skjærven
- Department
of Biomedicine, University of Bergen, Bergen, Norway
| | - Illimar Rekand
- Department
of Chemistry and Centre for Pharmacy, University of Bergen, Bergen, Norway
| | - Hanna-Kirsti S. Leiros
- The
Norwegian Structural Biology Centre (NorStruct), Department of Chemistry, UiT The Arctic University of Norway, Tromsø, Norway
| | - Bengt Erik Haug
- Department
of Chemistry and Centre for Pharmacy, University of Bergen, Bergen, Norway
| | - Nicholas P. Cianciotto
- Department
of Microbiology and Immunology, Northwestern University Medical School, Chicago, Illinois 60611, United States
| | - Aurora Martinez
- Department
of Biomedicine, University of Bergen, Bergen, Norway
| | - Jarl Underhaug
- Department
of Biomedicine, University of Bergen, Bergen, Norway
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16
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de Paula DAJ, Rosa e Silva LK, Staats CC, Vainstein MH, Joanoni ALP, Nakazato L, Dutra V. Identification of genes expressed by Cryptococcus gattii during iron deprivation. Braz J Microbiol 2014; 45:813-20. [PMID: 25477912 PMCID: PMC4204963 DOI: 10.1590/s1517-83822014000300008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Accepted: 12/13/2013] [Indexed: 11/23/2022] Open
Abstract
Cryptococcus neoformans and C. gattii are pathogenic yeasts that cause life-threatening diseases in humans and animals. Iron is an essential nutrient for virtually every organism as it functions as a cofactor in numerous essential enzymatic reactions. In the literature, the competition for iron between microbes and mammalian hosts during infection is well documented. In this study, we used representational difference analysis (RDA) in order to gain a better understanding of how C. gattii responds to iron starvation. A total of 15 and 29 genes were identified as having altered expression levels due to iron depletion after 3 h and 12 h, respectively. Of these, eight genes were identified in both libraries. The transcripts were related to many biological processes, such as cell cycle, ergosterol metabolism, cell wall organization, transportation, translation, cell respiration and the stress response. These data suggest a remodeling of C. gattii metabolism during conditions of iron deprivation.
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Affiliation(s)
| | - Lívia Kmetzsch Rosa e Silva
- Centro de Biotecnologia Universidade Federal do Rio Grande do Sul Porto AlegreRS Brazil Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Charley Christian Staats
- Centro de Biotecnologia Universidade Federal do Rio Grande do Sul Porto AlegreRS Brazil Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Marilene H Vainstein
- Centro de Biotecnologia Universidade Federal do Rio Grande do Sul Porto AlegreRS Brazil Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - Ana Lúcia Pinto Joanoni
- Universidade Federal de Mato Grosso CuiabáMT Brazil Universidade Federal de Mato Grosso, Cuiabá, MT, Brazil
| | - Luciano Nakazato
- Universidade Federal de Mato Grosso CuiabáMT Brazil Universidade Federal de Mato Grosso, Cuiabá, MT, Brazil
| | - Valéria Dutra
- Universidade Federal de Mato Grosso CuiabáMT Brazil Universidade Federal de Mato Grosso, Cuiabá, MT, Brazil
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17
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Abstract
Fungal pathogens must assimilate local nutrients to establish an infection in their mammalian host. We focus on carbon, nitrogen, and micronutrient assimilation mechanisms, discussing how these influence host-fungus interactions during infection. We highlight several emerging trends based on the available data. First, the perturbation of carbon, nitrogen, or micronutrient assimilation attenuates fungal pathogenicity. Second, the contrasting evolutionary pressures exerted on facultative versus obligatory pathogens have led to contemporary pathogenic fungal species that display differing degrees of metabolic flexibility. The evolutionarily ancient metabolic pathways are conserved in most fungal pathogen, but interesting gaps exist in some species (e.g., Candida glabrata). Third, metabolic flexibility is generally essential for fungal pathogenicity, and in particular, for the adaptation to contrasting host microenvironments such as the gastrointestinal tract, mucosal surfaces, bloodstream, and internal organs. Fourth, this metabolic flexibility relies on complex regulatory networks, some of which are conserved across lineages, whereas others have undergone significant evolutionary rewiring. Fifth, metabolic adaptation affects fungal susceptibility to antifungal drugs and also presents exciting opportunities for the development of novel therapies.
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Affiliation(s)
- Iuliana V Ene
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Sascha Brunke
- Department of Microbial Pathogenicity Mechanisms, Hans Knoell Institute, 07745 Jena, Germany
| | - Alistair J P Brown
- Aberdeen Fungal Group, School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom
| | - Bernhard Hube
- Department of Microbial Pathogenicity Mechanisms, Hans Knoell Institute, 07745 Jena, Germany Friedrich Schiller University, 07743 Jena, Germany Center for Sepsis Control and Care, Universitätsklinikum Jena, 07747 Jena, Germany
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18
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Ding C, Festa RA, Sun TS, Wang ZY. Iron and copper as virulence modulators in human fungal pathogens. Mol Microbiol 2014; 93:10-23. [PMID: 24851950 DOI: 10.1111/mmi.12653] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2014] [Indexed: 01/22/2023]
Abstract
Fungal pathogens have evolved sophisticated machinery to precisely balance the fine line between acquiring essential metals and defending against metal toxicity. Iron and copper are essential metals for many processes in both fungal pathogens and their mammalian hosts, but reduce viability when present in excess. However, during infection, the host uses these two metals differently. Fe has a long-standing history of influencing virulence in pathogenic fungi, mostly in regards to Fe acquisition. Numerous studies demonstrate the requirement of the Fe acquisition pathway of Candida, Cryptococcus and Aspergillus for successful systemic infection. Fe is not free in the host, but is associated with Fe-binding proteins, leading fungi to develop mechanisms to interact with and to acquire Fe from these Fe-bound proteins. Cu is also essential for cell growth and development. Essential Cu-binding proteins include Fe transporters, superoxide dismutase (SOD) and cytochrome c oxidase. Although Cu acquisition plays critical roles in fungal survival in the host, recent work has revealed that Cu detoxification is extremely important. Here, we review fungal responses to altered metal conditions presented by the host, contrast the roles of Fe and Cu during infection, and outline the critical roles of fungal metal homeostasis machinery at the host-pathogen axis.
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Affiliation(s)
- Chen Ding
- College of Life and Health Sciences, Northeastern University, Shenyang, Liaoning, China
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19
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Grabo JE, Chrisman MA, Webb LM, Baldwin MJ. Photochemical Reactivity of the Iron(III) Complex of a Mixed-Donor, α-Hydroxy Acid-Containing Chelate and Its Biological Relevance to Photoactive Marine Siderophores. Inorg Chem 2014; 53:5781-7. [DOI: 10.1021/ic500635q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jennifer E. Grabo
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, Ohio 45221-0172, United States
| | - Mark A. Chrisman
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, Ohio 45221-0172, United States
| | - Lindsay M. Webb
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, Ohio 45221-0172, United States
| | - Michael J. Baldwin
- Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati, Ohio 45221-0172, United States
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20
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Microevolution during serial mouse passage demonstrates FRE3 as a virulence adaptation gene in Cryptococcus neoformans. mBio 2014; 5:e00941-14. [PMID: 24692633 PMCID: PMC3977352 DOI: 10.1128/mbio.00941-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Passage in mice of opportunistic pathogens such as Cryptococcus neoformans is known to increase virulence, but little is known about the molecular mechanisms involved in virulence adaptation. Serial mouse passage of nine environmental strains of serotype A C. neoformans identified two highly adapted virulent strains that showed a 4-fold reduction in time to death after four passages. Transcriptome sequencing expression studies demonstrated increased expression of a FRE3-encoded iron reductase in the two strains but not in a control strain that did not demonstrate increased virulence during mouse passage. FRE3 was shown to express an iron reductase activity and to play a role in iron-dependent growth of C. neoformans. Overexpression of FRE3 in the two original environmental strains increased growth in the macrophage cell line J774.16 and increased virulence. These data demonstrate a role for FRE3 in the virulence of C. neoformans and demonstrate how the increased expression of such a "virulence acquisition gene" during the environment-to-mammal transition, can optimize the virulence of environmental strains in mammalian hosts. IMPORTANCE Cryptococcus neoformans is a significant global fungal pathogen that also resides in the environment. Recent studies have suggested that the organism may undergo microevolution in the host. However, little is known about the permitted genetic changes facilitating the adaptation of environmental strains to mammalian hosts. The present studies subjected environmental strains isolated from several metropolitan areas of the United States to serial passages in mice. Transcriptome sequencing expression studies identified the increased expression of an iron reductase gene, FRE3, in two strains that adapted in mice to become highly virulent, and overexpression of FRE3 recapitulated the increased virulence after mouse passage. Iron reductase in yeast is important to iron uptake in a large number of microbial pathogens. These studies demonstrate the capacity of C. neoformans to show reproducible changes in the expression levels of small numbers of genes termed "virulence adaptation genes" to effectively increase pathogenicity during the environment-to-mammal transition.
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21
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Saraiva M, de Bruijn I, Grenville-Briggs L, McLaggan D, Willems A, Bulone V, van West P. Functional characterization of a tyrosinase gene from the oomycete Saprolegnia parasitica by RNAi silencing. Fungal Biol 2014; 118:621-9. [PMID: 25088076 PMCID: PMC4152626 DOI: 10.1016/j.funbio.2014.01.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 01/17/2014] [Accepted: 01/24/2014] [Indexed: 02/04/2023]
Abstract
Here we describe the first application of transient gene silencing in Saprolegnia parasitica, a pathogenic oomycete that infects a wide range of fish, amphibians, and crustaceans. A gene encoding a putative tyrosinase from S. parasitica, SpTyr, was selected to investigate the suitability of RNA-interference (RNAi) to functionally characterize genes of this economically important pathogen. Tyrosinase is a mono-oxygenase enzyme that catalyses the O-hydroxylation of monophenols and subsequent oxidation of O-diphenols to quinines. These enzymes are widely distributed in nature, and are involved in the melanin biosynthesis. Gene silencing was obtained by delivering in vitro synthesized SpTyr dsRNA into protoplasts. Expression analysis, tyrosinase activity measurements, and melanin content analysis confirmed silencing in individual lines. Silencing of SpTyr resulted in a decrease of tyrosinase activity between 38 % and 60 %, dependent on the level of SpTyr-expression achieved. The SpTyr-silenced lines displayed less pigmentation in developing sporangia and occasionally an altered morphology. Moreover, developing sporangia from individual silenced lines possessed a less electron dense cell wall when compared to control lines, treated with GFP-dsRNA. In conclusion, the tyrosinase gene of S. parasitica is required for melanin formation and transient gene silencing can be used to functionally characterize genes in S. parasitica. Successful transient gene silencing in Saprolegnia parasitica through RNAi. Silencing a tyrosinase in S. parasitica results in reduced melanin formation. Silencing a tyrosinase in S. parasitica results in aberrant sporangia formation.
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Affiliation(s)
- Marcia Saraiva
- Aberdeen Oomycete Laboratory, University of Aberdeen, Foresterhill, AB25 2ZD Aberdeen, UK
| | - Irene de Bruijn
- Aberdeen Oomycete Laboratory, University of Aberdeen, Foresterhill, AB25 2ZD Aberdeen, UK
| | - Laura Grenville-Briggs
- Aberdeen Oomycete Laboratory, University of Aberdeen, Foresterhill, AB25 2ZD Aberdeen, UK; Division of Glycoscience, School of Biotechnology, KTH - Royal Institute of Technology, AlbaNova University Center, SE-106 91 Stockholm, Sweden
| | - Debbie McLaggan
- Aberdeen Oomycete Laboratory, University of Aberdeen, Foresterhill, AB25 2ZD Aberdeen, UK
| | - Ariane Willems
- Aberdeen Oomycete Laboratory, University of Aberdeen, Foresterhill, AB25 2ZD Aberdeen, UK
| | - Vincent Bulone
- Division of Glycoscience, School of Biotechnology, KTH - Royal Institute of Technology, AlbaNova University Center, SE-106 91 Stockholm, Sweden
| | - Pieter van West
- Aberdeen Oomycete Laboratory, University of Aberdeen, Foresterhill, AB25 2ZD Aberdeen, UK.
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22
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Jung WH, Do E. Iron acquisition in the human fungal pathogen Cryptococcus neoformans. Curr Opin Microbiol 2013; 16:686-91. [DOI: 10.1016/j.mib.2013.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Revised: 07/11/2013] [Accepted: 07/11/2013] [Indexed: 11/24/2022]
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23
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Caza M, Kronstad JW. Shared and distinct mechanisms of iron acquisition by bacterial and fungal pathogens of humans. Front Cell Infect Microbiol 2013; 3:80. [PMID: 24312900 PMCID: PMC3832793 DOI: 10.3389/fcimb.2013.00080] [Citation(s) in RCA: 178] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Accepted: 10/30/2013] [Indexed: 12/12/2022] Open
Abstract
Iron is the most abundant transition metal in the human body and its bioavailability is stringently controlled. In particular, iron is tightly bound to host proteins such as transferrin to maintain homeostasis, to limit potential damage caused by iron toxicity under physiological conditions and to restrict access by pathogens. Therefore, iron acquisition during infection of a human host is a challenge that must be surmounted by every successful pathogenic microorganism. Iron is essential for bacterial and fungal physiological processes such as DNA replication, transcription, metabolism, and energy generation via respiration. Hence, pathogenic bacteria and fungi have developed sophisticated strategies to gain access to iron from host sources. Indeed, siderophore production and transport, iron acquisition from heme and host iron-containing proteins such as hemoglobin and transferrin, and reduction of ferric to ferrous iron with subsequent transport are all strategies found in bacterial and fungal pathogens of humans. This review focuses on a comparison of these strategies between bacterial and fungal pathogens in the context of virulence and the iron limitation that occurs in the human body as a mechanism of innate nutritional defense.
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Affiliation(s)
| | - James W. Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British ColumbiaVancouver, BC, Canada
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24
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Kronstad JW, Hu G, Jung WH. An encapsulation of iron homeostasis and virulence in Cryptococcus neoformans. Trends Microbiol 2013; 21:457-65. [PMID: 23810126 DOI: 10.1016/j.tim.2013.05.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 05/24/2013] [Accepted: 05/29/2013] [Indexed: 02/07/2023]
Abstract
Vertebrate hosts actively sequester iron, and fungal and other pathogens must therefore adapt to a severe limitation in iron availability to cause disease. Recent studies reveal that the pathogenic fungus Cryptococcus neoformans overcomes iron limitation by multiple mechanisms that target transferrin and heme. The regulation of iron uptake is mediated by an interconnected set of transcription factors that include the master iron regulator Cir1 and the pH-responsive factor Rim101. These factors integrate iron homeostasis with a myriad of other functions including pH sensing, nutrient and stress signaling pathways, virulence factor elaboration, and cell wall biogenesis.
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Affiliation(s)
- James W Kronstad
- Department of Microbiology and Immunology, The Michael Smith Laboratories, University of British Columbia, Vancouver BC, V6T 1Z4, Canada.
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25
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Jain N, Cordero RJB, Casadevall A, Fries BC. Allergen1 regulates polysaccharide structure in Cryptococcus neoformans. Mol Microbiol 2013; 88:713-27. [PMID: 23565821 DOI: 10.1111/mmi.12216] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/21/2013] [Indexed: 12/19/2022]
Abstract
Cryptococcus neoformans is an important human, fungal pathogen that sheds polysaccharide (exo-PS) into host tissues. While shed exo-PS mediates numerous untoward effects (including promoting increased intracranial pressure), little is known about the regulation of this phenomenon. Since downregulation of the Allergen 1 (ALL1) gene is associated with high ICP, we investigated the relationship between ALL1 expression and exo-PS structure using a variety of biophysical techniques. The Δall1 mutants of two serotypes produced a shorter exo-PS with less branching and structural complexity than the parental strains. Consistent with lower branching, these exo-PSs manifested higher intrinsic viscosity than the parental strains. The Δall1 mutant strains manifested differences in epitope expression and significant resistance to phagocytosis. Exo-PS of Δall1 mutant exhibited anti-phagocytic properties. Comparative transcriptome analysis of mutant and parental strain under iron-deprived conditions indicated a role of ALL1 in iron homeostasis, characterized by differential regulation of genes that mediate iron reduction and transport. Together, our results demonstrate a role of ALL1 in regulating conformational aspects of PS structure and iron homeostasis. These findings provide a mechanism to explain how changes in ALL1 expression influence virulence of switch variants and suggest that structural changes and polymer length are epigenetically regulated.
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Affiliation(s)
- Neena Jain
- Department of Microbiology and Immunology, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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26
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Adaptation of Cryptococcus neoformans to mammalian hosts: integrated regulation of metabolism and virulence. EUKARYOTIC CELL 2011; 11:109-18. [PMID: 22140231 DOI: 10.1128/ec.05273-11] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The basidiomycete fungus Cryptococcus neoformans infects humans via inhalation of desiccated yeast cells or spores from the environment. In the absence of effective immune containment, the initial pulmonary infection often spreads to the central nervous system to result in meningoencephalitis. The fungus must therefore make the transition from the environment to different mammalian niches that include the intracellular locale of phagocytic cells and extracellular sites in the lung, bloodstream, and central nervous system. Recent studies provide insights into mechanisms of adaptation during this transition that include the expression of antiphagocytic functions, the remodeling of central carbon metabolism, the expression of specific nutrient acquisition systems, and the response to hypoxia. Specific transcription factors regulate these functions as well as the expression of one or more of the major known virulence factors of C. neoformans. Therefore, virulence factor expression is to a large extent embedded in the regulation of a variety of functions needed for growth in mammalian hosts. In this regard, the complex integration of these processes is reminiscent of the master regulators of virulence in bacterial pathogens.
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Lessons from Cryptococcal Laccase: From Environmental Saprophyte to Pathogen. CURRENT FUNGAL INFECTION REPORTS 2011. [DOI: 10.1007/s12281-011-0069-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Crestani J, Carvalho PC, Han X, Seixas A, Broetto L, Fischer JDSDG, Staats CC, Schrank A, Yates JR, Vainstein MH. Proteomic profiling of the influence of iron availability on Cryptococcus gattii. J Proteome Res 2011; 11:189-205. [PMID: 21970549 DOI: 10.1021/pr2005296] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Iron is essential and ubiquitous in living organisms. The competition for this micronutrient between the host and its pathogens has been related to disease establishment. Cryptococcus gattii is an encapsulated yeast that causes cryptococcosis mainly in immunocompetent individuals. In this study, we analyzed the proteomic profile of the C. gattii R265 Vancouver Island isolate under iron-depleted and -repleted conditions by multidimensional protein identification technology (MudPIT) and by 2D-GE. Proteins and key mechanisms affected by alteration of iron levels such as capsule production, cAMP-signaling pathway, response to stress, and metabolic pathways related to mitochondrial function were identified. Our results also show both proteomic methodologies employed to be complementary.
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Affiliation(s)
- Juliana Crestani
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, 43421, Caixa Postal 15005, Porto Alegre, RS 91501-970, Brazil
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Urán ME, Nosanchuk JD, Restrepo A, Hamilton AJ, Gómez BL, Cano LE. Detection of antibodies against Paracoccidioides brasiliensis melanin in in vitro and in vivo studies during infection. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2011; 18:1680-8. [PMID: 21813659 PMCID: PMC3187017 DOI: 10.1128/cvi.05099-11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Accepted: 07/26/2011] [Indexed: 12/18/2022]
Abstract
Several cell wall constituents, including melanins or melanin-like compounds, have been implicated in the pathogenesis of a wide variety of microbial diseases caused by diverse species of pathogenic bacteria, fungi, and helminthes. Among these microorganisms, the dimorphic fungal pathogen Paracoccidioides brasiliensis produces melanin in its conidial and yeast forms. In the present study, melanin particles from P. brasiliensis were injected into BALB/c mice in order to produce monoclonal antibodies (MAbs). We identified five immunoglobulin G1 (IgG1) κ-chain and four IgM melanin-binding MAbs. The five IgG1 κ-chain isotypes are the first melanin-binding IgG MAbs ever reported. The nine MAbs labeled P. brasiliensis conidia and yeast cells both in vitro and in pulmonary tissues. The MAbs cross-reacted with melanin-like purified particles from other fungi and also with commercial melanins, such as synthetic and Sepia officinalis melanin. Melanization during paracoccidioidomycosis (PCM) was also further supported by the detection of IgG antibodies reactive to melanin from P. brasiliensis conidia and yeast in sera and bronchoalveolar lavage fluids from P. brasiliensis-infected mice, as well as in sera from human patients with PCM. Serum specimens from patients with other mycoses were also tested for melanin-binding antibodies by enzyme-linked immunosorbent assay, and cross-reactivities were detected for melanin particles from different fungal sources. These results suggest that melanin from P. brasiliensis is an immunologically active fungal structure that activates a strong IgG humoral response in humans and mice.
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Affiliation(s)
- Martha E Urán
- Medical and Experimental Mycology Unit, Corporación para Investigaciones Biológicas, Carrera 72A No. 78B-141, A.A. 73-78, Medellín, Colombia.
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Blatzer M, Binder U, Haas H. The metalloreductase FreB is involved in adaptation of Aspergillus fumigatus to iron starvation. Fungal Genet Biol 2011; 48:1027-33. [PMID: 21840411 PMCID: PMC3188701 DOI: 10.1016/j.fgb.2011.07.009] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 07/25/2011] [Accepted: 07/26/2011] [Indexed: 01/10/2023]
Abstract
Aspergillus fumigatus employs two high affinity iron uptake mechanisms, siderophore mediated iron uptake and reductive iron assimilation (RIA). The A. fumigatus genome encodes 15 putative metalloreductases (MR) but the ferrireductases involved in RIA remained elusive so far. Expression of the MR FreB was found to be transcriptionally repressed by iron via SreA, a repressor of iron acquisition during iron sufficiency, indicating a role in iron metabolism. FreB-inactivation by gene deletion was phenotypically largely inconspicuous unless combined with inactivation of the siderophore system, which then decreased growth rate, surface ferrireductase activity and oxidative stress resistance during iron starvation. This study also revealed that loss of copper-independent siderophore-mediated iron uptake increases sensitivity of A. fumigatus to copper starvation due to copper-dependence of RIA.
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Affiliation(s)
- Michael Blatzer
- Division of Molecular Biology/Biocenter, Fritz-Pregl-Str. 3, Innsbruck Medical University, A-6020 Innsbruck, Austria
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31
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Turick CE, Ekechukwu AA, Milliken CE, Casadevall A, Dadachova E. Gamma radiation interacts with melanin to alter its oxidation-reduction potential and results in electric current production. Bioelectrochemistry 2011; 82:69-73. [PMID: 21632287 DOI: 10.1016/j.bioelechem.2011.04.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Revised: 03/23/2011] [Accepted: 04/04/2011] [Indexed: 11/19/2022]
Abstract
The presence of melanin pigments in organisms is implicated in radioprotection and in some cases, enhanced growth in the presence of high levels of ionizing radiation. An understanding of this phenomenon will be useful in the design of radioprotective materials. However, the protective mechanism of microbial melanin in ionizing radiation fields has not yet been elucidated. Here we demonstrate through the electrochemical techniques of chronoamperometry, chronopotentiometry and cyclic voltammetry that microbial melanin is continuously oxidized in the presence of gamma radiation. Our findings establish that ionizing radiation interacts with melanin to alter its oxidation-reduction potential. Sustained oxidation resulted in electric current production and was most pronounced in the presence of a reductant, which extended the redox cycling capacity of melanin. This work is the first to establish that gamma radiation alters the oxidation-reduction behavior of melanin, resulting in electric current production. The significance of the work is that it provides the first step in understanding the initial interactions between melanin and ionizing radiation taking place and offers some insight for production of biomimetic radioprotective materials.
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Affiliation(s)
- Charles E Turick
- Biotechnology Section, Savannah River National Laboratory, Aiken, SC 29808, USA.
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32
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Nevitt T. War-Fe-re: iron at the core of fungal virulence and host immunity. Biometals 2011; 24:547-58. [PMID: 21399939 DOI: 10.1007/s10534-011-9431-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Accepted: 02/22/2011] [Indexed: 12/21/2022]
Abstract
Iron acquisition is a bona fide virulence determinant. The successful colonization of the mammalian host requires that microorganisms overcome the Fe aridity of this milieu in which the levels of circulating Fe are maintained exceedingly low both through the compartmentalization of this nutrient within cells as well as the tight binding of Fe to host circulating proteins and ligands. Microbes notoriously employ multiple strategies for high affinity Fe acquisition from the host that rely either on the expression of receptors for host Fe-binding proteins and ligands, its reduction by cell surface reductases or the utilization of siderophores, small organic molecules with very high affinity for Fe(3+). This review will discuss the multiple mechanisms deployed by fungal pathogens in Fe acquisition focusing on the role of siderophore utilization in virulence as well as host immune strategies of iron withholding and emerging clinical evidence that human disorders of Fe homeostasis can act as modifiers of infectious disease.
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Affiliation(s)
- Tracy Nevitt
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA.
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Glanfield A, McManus DP, Smyth DJ, Lovas EM, Loukas A, Gobert GN, Jones MK. A cytochrome b561 with ferric reductase activity from the parasitic blood fluke, Schistosoma japonicum. PLoS Negl Trop Dis 2010; 4:e884. [PMID: 21103361 PMCID: PMC2982821 DOI: 10.1371/journal.pntd.0000884] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Accepted: 10/18/2010] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND Iron has an integral role in numerous cellular reactions and is required by virtually all organisms. In physiological conditions, iron is abundant in a largely insoluble ferric state. Ferric reductases are an essential component of iron uptake by cells, reducing iron to the soluble ferrous form. Cytochromes b561 (cyts-b561) are a family of ascorbate reducing transmembrane proteins found in most eukaryotic cells. The identification of the ferric reductase duodenal cytochrome b (dcytb) and recent observations that other cyts-b561 may be involved in iron metabolism have opened novel perspectives for elucidating their physiological function. METHODOLOGY/PRINCIPAL FINDINGS Here we have identified a new member of the cytochrome b561 (Sjcytb561) family in the pathogenic blood fluke Schistosoma japonicum that localises to the outer surface of this parasitic trematode. Heterologous expression of recombinant Sjcyt-b561 in a Saccharomyces cerevisiae mutant strain that lacks plasma membrane ferrireductase activity demonstrated that the molecule could rescue ferric reductase activity in the yeast. SIGNIFICANCE/CONCLUSIONS This finding of a new member of the cytochrome b561 family further supports the notion that a ferric reductase function is likely for other members of this protein family. Additionally, the localisation of Sjcytb561 in the surface epithelium of these blood-dwelling schistosomes contributes further to our knowledge concerning nutrient acquisition in these parasites and may provide novel targets for therapeutic intervention.
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Affiliation(s)
- Amber Glanfield
- Queensland Institute of Medical Research, Herston, Queensland, Australia
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Raza W, Shen Q. Growth, Fe3+ reductase activity, and siderophore production by Paenibacillus polymyxa SQR-21 under differential iron conditions. Curr Microbiol 2010; 61:390-5. [PMID: 20358373 DOI: 10.1007/s00284-010-9624-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2009] [Accepted: 03/16/2010] [Indexed: 10/19/2022]
Abstract
An experiment was planned to evaluate the behavior of Paenibacillus polymyxa SQR-21 under differential iron availability. P. polymyxa was grown under three differential iron conditions (0, 2, 20 μM). Iron starvation slowed bacterial growth and at all iron levels, pH of liquid culture was decreased, but maximum decrease was observed at highest iron level. Cell surface ferrireductase activity decreased as culture aged, while extracellular Fe(3+)-reducing activity constantly increased. Hydroxamates type siderophores production was increased with the decrease in iron levels. Numerous cellular proteins were expressed by P. polymyxa in the range of 5-140 kDa and several of them showed conspicuous differential iron regulation. P. polymyxa seems to have more than one type of iron acquisition mechanism including gradual release of organic acids, cell surface ferrireductases, extracellular reductants, and secretion of low molecular weight hydroxamates chelators. This article is the first to report the kinetic study of P. polymyxa under differential iron availability. The information provided here gives initial information about the iron uptake mechanism of P. polymyxa.
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Affiliation(s)
- Waseem Raza
- Jiangsu Key Laboratory for Organic Waste Utilization, Nanjing Agricultural University, Nanjing, Jiangsu Province, People's Republic of China
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35
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Liu GY, Nizet V. Color me bad: microbial pigments as virulence factors. Trends Microbiol 2009; 17:406-13. [PMID: 19726196 PMCID: PMC2743764 DOI: 10.1016/j.tim.2009.06.006] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 06/06/2009] [Accepted: 06/08/2009] [Indexed: 01/23/2023]
Abstract
A hallmark feature of several pathogenic microbes is the distinctive color of their colonies when propagated in the clinical laboratory. Such pigmentation comes in a variety of hues, and has often proven useful in presumptive clinical diagnosis. Recent advances in microbial pigment biochemistry and the genetic basis of pigment production have sometimes revealed a more sinister aspect to these curious materials that change the color of reflected light by selective light absorbance. In many cases, the microbial pigment contributes to disease pathogenesis by interfering with host immune clearance mechanisms or by exhibiting pro-inflammatory or cytotoxic properties. We review several examples of pigments that promote microbial virulence, including the golden staphyloxanthin of Staphylococcusaureus, the blue-green pyocyanin of Pseudomonas spp., and the dark brown or black melanin pigments of Cryptococcus neoformans and Aspergillus spp. Targeted pigment neutralisation might represent a viable concept to enhance treatment of certain difficult infectious disease conditions.
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Affiliation(s)
- George Y Liu
- Division of Pediatric Infectious Diseases and Immunobiology Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
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36
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Kornitzer D. Fungal mechanisms for host iron acquisition. Curr Opin Microbiol 2009; 12:377-83. [PMID: 19540796 DOI: 10.1016/j.mib.2009.05.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2009] [Revised: 04/29/2009] [Accepted: 05/12/2009] [Indexed: 11/29/2022]
Abstract
The iron scarcity in the host environment presents a challenge for infecting microorganisms. Fungi can assimilate iron via reductive, nonreductive, and host molecule-specific mechanisms. Recent developments in the characterization of iron acquisition mechanisms in the four best-studied fungal pathogens reveal commonalities and differences in those mechanisms as well as in their regulatory pathways.
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Affiliation(s)
- Daniel Kornitzer
- Department of Molecular Microbiology, B. Rappaport Faculty of Medicine, Technion-IIT, Haifa, Israel.
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Jung WH, Sham A, Lian T, Singh A, Kosman DJ, Kronstad JW. Iron source preference and regulation of iron uptake in Cryptococcus neoformans. PLoS Pathog 2008; 4:e45. [PMID: 18282105 PMCID: PMC2242830 DOI: 10.1371/journal.ppat.0040045] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Accepted: 01/07/2008] [Indexed: 01/09/2023] Open
Abstract
The level of available iron in the mammalian host is extremely low, and pathogenic microbes must compete with host proteins such as transferrin for iron. Iron regulation of gene expression, including genes encoding iron uptake functions and virulence factors, is critical for the pathogenesis of the fungus Cryptococcus neoformans. In this study, we characterized the roles of the CFT1 and CFT2 genes that encode C. neoformans orthologs of the Saccharomyces cerevisiae high-affinity iron permease FTR1. Deletion of CFT1 reduced growth and iron uptake with ferric chloride and holo-transferrin as the in vitro iron sources, and the cft1 mutant was attenuated for virulence in a mouse model of infection. A reduction in the fungal burden in the brains of mice infected with the cft1 mutant was observed, thus suggesting a requirement for reductive iron acquisition during cryptococcal meningitis. CFT2 played no apparent role in iron acquisition but did influence virulence. The expression of both CFT1 and CFT2 was influenced by cAMP-dependent protein kinase, and the iron-regulatory transcription factor Cir1 positively regulated CFT1 and negatively regulated CFT2. Overall, these results indicate that C. neoformans utilizes iron sources within the host (e.g., holo-transferrin) that require Cft1 and a reductive iron uptake system. Opportunistic fungal pathogens and other invading microbes must overcome extreme iron limitation to proliferate in the mammalian host. It is not yet known which iron sources are preferred by fungal pathogens of mammals, although the mechanisms of acquisition are beginning to be explored. Some fungi produce iron-chelating siderophores to capture iron from host proteins, while others appear to require a membrane-bound iron permease–ferroxidase system. We describe the ability of the encapsulated yeast Cryptococcus neoformans to use host iron sources including transferrin and heme, and we identify an iron permease that is required for full disease progression in experimental mouse models. The permease is required for iron utilization from transferrin but not heme during growth in laboratory culture. This result when combined with the observed slow growth of the permease mutant during the experimental infections implicates transferrin as an important iron source in the host. However, we find that mutants lacking the permease eventually do cause disease, thus revealing that additional iron sources such as heme and other uptake mechanisms are available to C. neoformans. Finally, we noted that the permease mutant showed particularly poor growth in the brains of infected animals, suggesting that transferrin may be an especially important iron source in this tissue.
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Affiliation(s)
- Won Hee Jung
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Anita Sham
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Tianshun Lian
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Arvinder Singh
- Department of Biochemistry, School of Medicine and Biomedical Sciences, The University at Buffalo, Buffalo, New York, United States of America
| | - Daniel J Kosman
- Department of Biochemistry, School of Medicine and Biomedical Sciences, The University at Buffalo, Buffalo, New York, United States of America
| | - James W Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
- * To whom correspondence should be addressed. E-mail:
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Turick CE, Knox AS, Leverette CL, Kritzas YG. In situ uranium stabilization by microbial metabolites. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2008; 99:890-899. [PMID: 18222573 DOI: 10.1016/j.jenvrad.2007.11.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/09/2007] [Indexed: 05/25/2023]
Abstract
Microbial melanin production by autochthonous bacteria was explored in this study as a means to increase U immobilization in U contaminated soil. This article demonstrates the application of bacterial physiology and soil ecology for enhanced U immobilization in order to develop an in situ, U bio-immobilization technology. We have demonstrated microbial production of a metal chelating biopolymer, pyomelanin, in U contaminated soil from the Tims Branch area of the Department of Energy (DOE), Savannah River Site (SRS), South Carolina, as a result of tyrosine amendments. Bacterial densities of pyomelanin producers were >10(6) cells per g wet soil. Pyomelanin demonstrated U complexing and mineral binding capacities at pH 4 and 7. In laboratory studies, in the presence of goethite or illite, pyomelanin enhanced U sequestration by these minerals. Tyrosine amended soils in a field test demonstrated increased U sequestration capacity following pyomelanin production up to 13 months after tyrosine treatments.
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Affiliation(s)
- Charles E Turick
- Environmental Science and Biotechnology, Savannah River National Laboratory, Building 999W, Aiken, SC 29808, USA.
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Arantes V, Milagres AMF. Response of Wolfiporia cocos to iron availability: alterations in growth, expression of cellular proteins, Fe3+-reducing activity and Fe3+-chelators production. J Appl Microbiol 2008; 104:185-93. [PMID: 17850312 DOI: 10.1111/j.1365-2672.2007.03540.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIMS The main objective of this study was to evaluate the behaviour of the brown-rot fungus Wolfiporia cocos under differential iron availability. METHODS AND RESULTS W. cocos was grown under three differential iron conditions. Growth, catecholate and hydroxamate production, and mycelial and extracellular Fe3+-reducing activities were determined. Iron starvation slowed fungal growth and accelerated pH decline. Some mycelial proteins of low molecular weight were repressed under iron restriction, whereas others of high molecular weight showed positive iron regulation. Mycelial ferrireductase activity decreased as culture aged, while Fe3+-reducing activity of low molecular reductants constantly increased. Hydroxamates production suffered only limited iron repression, whereas catecholates production showed to be more iron repressible. CONCLUSIONS W. cocos seems to possess more than one type of iron acquisition mechanism; one involving secretion of organic acids and ferrireductases and/or extracellular reductants, and another relying on secretion of catecholates and hydroxamates chelators. SIGNIFICANCE AND IMPACT OF THE STUDY This paper is the first to report the kinetic study of brown-rot fungus grown under differential iron availability, and the information provided here contributes to address more traditional problems in protecting wood from brown decay, and also makes a contribution in the general area of the physiology of brown-rot fungi.
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Affiliation(s)
- V Arantes
- Department of Biotechnology, Escola de Engenharia de Lorena, University of São Paulo - USP Lorena, Lorena/SP, Brazil.
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Turick CE, Caccavo F, Tisa LS. Pyomelanin is produced by Shewanella algae BrY and affected by exogenous iron. Can J Microbiol 2008; 54:334-9. [DOI: 10.1139/w08-014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Melanin production by Shewanella algae BrY occurred during late- and (or) post-exponential growth in lactate basal salts liquid medium supplemented with tyrosine or phenylalanine. The antioxidant ascorbate inhibited melanin production but not production of the melanin precursor homogentisic acid. In the absence of ascorbate, melanin production was inhibited by the 4-hydroxyphenylpyruvate dioxygenase inhibitor sulcotrione and by concentrations of Fe ≥ 0.38 mmol·L–1. These data support the hypothesis that pigment production by S. algae BrY was a result of the conversion of tyrosine or phenylalanine to homogentisic acid, which was excreted, auto-oxidized, and self-polymerized to form pyomelanin. Pyomelanin production by S. algae BrY may play an important role in the biogeochemical cycling of Fe in the environment.
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Affiliation(s)
- Charles E. Turick
- Environmental Biotechnology Section, Savannah River National Laboratory, Building 999W, Aiken, SC 29808, USA
- Department of Biology, Whitworth College, Spokane, WA 99251, USA
- Department of Microbiology, University of New Hampshire, Durham, NH 03824-2617, USA
| | - Frank Caccavo
- Environmental Biotechnology Section, Savannah River National Laboratory, Building 999W, Aiken, SC 29808, USA
- Department of Biology, Whitworth College, Spokane, WA 99251, USA
- Department of Microbiology, University of New Hampshire, Durham, NH 03824-2617, USA
| | - Louis S. Tisa
- Environmental Biotechnology Section, Savannah River National Laboratory, Building 999W, Aiken, SC 29808, USA
- Department of Biology, Whitworth College, Spokane, WA 99251, USA
- Department of Microbiology, University of New Hampshire, Durham, NH 03824-2617, USA
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Arantes V, Milagres AM. Identification of iron-regulated cellular proteins, Fe3+-reducing and -chelating compounds, in the white-rot fungus Perenniporia medulla-panis. Can J Microbiol 2007; 53:1323-9. [DOI: 10.1139/w07-102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In this paper, we present the responses of the white-rot fungus Perenniporia medulla-panis to iron availability with regard to alterations in growth, expression of cellular proteins, Fe3+-reducing activity, and Fe3+chelators production. Iron supplementation stimulated fungal growth but did not result in a significant increase in biomass production. Catechol and hydroxamate derivatives were produced mainly under iron deficiency, and their productions were repressed under iron supplementation conditions. Perenniporia medulla-panis showed several cellular proteins in the range of 10–90 kDa. Some of them showed negative iron-regulation. Iron-supplemented medium also repressed both cell surface and extracellular Fe3+-reducing activities; however, the highest cell surface activity was detected at the initial growth phase, whereas extracellular activity increased throughout the incubation period. No significant production of chelators and extracellular Fe3+-reducing activity were observed within the initial growth phase, suggesting that the reduction of Fe3+to Fe2+is performed by ferrireductases.
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Affiliation(s)
- Valdeir Arantes
- Department of Biotechnology, Escola de Engenharia de Lorena, University of São Paulo – USP Lorena, Estrada Municipal do Campinho, s/no. – Cx Postal 116, 12602-810 Lorena/SP, Brazil
| | - Adriane M.F. Milagres
- Department of Biotechnology, Escola de Engenharia de Lorena, University of São Paulo – USP Lorena, Estrada Municipal do Campinho, s/no. – Cx Postal 116, 12602-810 Lorena/SP, Brazil
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Jung WH, Kronstad JW. Iron and fungal pathogenesis: a case study with Cryptococcus neoformans. Cell Microbiol 2007; 10:277-84. [PMID: 18042257 DOI: 10.1111/j.1462-5822.2007.01077.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The acquisition of iron from mammalian hosts is an important aspect of infection because microbes must compete with the host for this nutrient and iron perception often regulates virulence factor expression. For example, iron levels are known to influence the elaboration of two major virulence factors, the polysaccharide capsule and melanin, in the pathogenic fungus Cryptococcus neoformans. This pathogen, which causes meningoencephalitis in immunocompromised people, acquires iron through the use of secreted reductants, cell surface reductases, a permease/ferroxidase uptake system and siderophore transporters. In addition, a master regulator, Cir1, integrates iron sensing with the expression of virulence factors, with growth at 37 degrees C and with signalling pathways that also influence virulence. The challenge ahead is to develop mechanistic views of the iron acquisition functions and regulatory schemes that operate when C. neoformans is in host tissue. Achieving these goals may contribute to an understanding of the notable predilection of the fungus for the mammalian central nervous system.
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Affiliation(s)
- Won Hee Jung
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
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44
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Growth and pigment production on D-tryptophan medium by Cryptococcus gattii, Cryptococcus neoformans, and Candida albicans. J Clin Microbiol 2007; 46:255-64. [PMID: 17989195 DOI: 10.1128/jcm.01721-07] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Given the increasing prevalence of cryptococcosis caused by Cryptococcus gattii (serotypes B and C) strains, there is a need for rapid and reliable tests that discriminate C. gattii from Cryptococcus neoformans (serotypes A, D, and AD). Seventy-two C. neoformans strains, sixty-seven C. gattii strains, and five Candida albicans strains were analyzed for their ability to grow and produce pigment on minimal D-tryptophan D-proline (m-DTDP) medium, on yeast carbon base D-tryptophan D-proline (YCB-DTDP) medium, and on fructose D-tryptophan glycine (m-FDTG) medium. Of the C. gattii and C. neoformans isolates, 94% and 0% grew on m-DTDP agar, respectively, and 98% and 0% grew in YCB-DTDP medium, respectively. C. gattii produced large amounts of brown intracellular pigment(s) on m-DTDP agar and smaller amounts of yellow-brown (amber) extracellular pigment(s). C. albicans grew on both media and produced a pink photoactivated pigment on m-DTDP agar. C. gattii produced large amounts of brown intracellular pigments on the differential medium m-FDTG, whereas C. neoformans produced smaller amounts of the brown pigments and C. albicans produced a pink pigment. The pigments produced by C. gattii from D-tryptophan were distinct and were not related to melanin formation from 3,4-dihydroxyphenylalanine. Thin-layer chromatography of the methanol-extracted C. gattii cells detected four different pigments, including brown (two types), yellow, and pink-purple compounds. We conclude that tryptophan-derived pigments are not melanins and that growth on m-DTDP or YCB-DTDP agar can be used to rapidly differentiate C. gattii from C. neoformans.
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Chatfield CH, Cianciotto NP. The secreted pyomelanin pigment of Legionella pneumophila confers ferric reductase activity. Infect Immun 2007; 75:4062-70. [PMID: 17548481 PMCID: PMC1951983 DOI: 10.1128/iai.00489-07] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The virulence of Legionella pneumophila is dependent upon its capacity to acquire iron. To identify genes involved in expression of its siderophore, we screened a mutagenized population of L. pneumophila for strains that were no longer able to rescue the growth of a ferrous transport mutant. However, an unusual mutant was obtained that displayed a strong inhibitory effect on the feoB mutant. Due to an insertion in hmgA that encodes homogentisate 1,2-dioxygenase, the mutant secreted increased levels of pyomelanin, the L. pneumophila pigment that is derived from secreted homogentisic acid (HGA). Thus, we hypothesized that L. pneumophila-secreted HGA-melanin has intrinsic ferric reductase activity, converting Fe(3+) to Fe(2+), but that hyperpigmentation results in excessive reduction of iron that can, in the case of the feoB mutant, be inhibitory to growth. In support of this hypothesis, we demonstrated, for the first time, that wild-type L. pneumophila secretes ferric reductase activity. Moreover, whereas the hyperpigmented mutant had increased secreted activity, an lly mutant specifically impaired for pigment production lacked the activity. Compatible with the nature of HGA-melanins, the secreted ferric reductase activity was positively influenced by the amount of tyrosine in the growth medium, resistant to protease, acid precipitable, and heterogeneous in size. Together, these data represent the first demonstration of pyomelanin-mediated ferric reduction by a pathogenic bacterium.
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Affiliation(s)
- Christa H Chatfield
- Department of Microbiology-Immunology, Northwestern University Medical School, 320 East Superior Street, Chicago, IL 60611-3010, USA
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Jung WH, Sham A, White R, Kronstad JW. Iron regulation of the major virulence factors in the AIDS-associated pathogen Cryptococcus neoformans. PLoS Biol 2007; 4:e410. [PMID: 17121456 PMCID: PMC1637126 DOI: 10.1371/journal.pbio.0040410] [Citation(s) in RCA: 176] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2006] [Accepted: 09/22/2006] [Indexed: 11/18/2022] Open
Abstract
Iron overload is known to exacerbate many infectious diseases, and conversely, iron withholding is an important defense strategy for mammalian hosts. Iron is a critical cue for Cryptococcus neoformans because the fungus senses iron to regulate elaboration of the polysaccharide capsule that is the major virulence factor during infection. Excess iron exacerbates experimental cryptococcosis and the prevalence of this disease in Sub-Saharan Africa has been associated with nutritional and genetic aspects of iron loading in the background of the HIV/AIDS epidemic. We demonstrate that the iron-responsive transcription factor Cir1 in Cr. neoformans controls the regulon of genes for iron acquisition such that cir1 mutants are "blind" to changes in external iron levels. Cir1 also controls the known major virulence factors of the pathogen including the capsule, the formation of the anti-oxidant melanin in the cell wall, and the ability to grow at host body temperature. Thus, the fungus is remarkably tuned to perceive iron as part of the disease process, as confirmed by the avirulence of the cir1 mutant; this characteristic of the pathogen may provide opportunities for antifungal treatment.
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Affiliation(s)
- Won Hee Jung
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Anita Sham
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Rick White
- Department of Statistics, University of British Columbia, Vancouver, British Columbia, Canada
| | - James W Kronstad
- The Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
- * To whom correspondence should be addressed. E-mail:
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Tangen KL, Jung WH, Sham AP, Lian T, Kronstad JW. The iron- and cAMP-regulated gene SIT1 influences ferrioxamine B utilization, melanization and cell wall structure in Cryptococcus neoformans. MICROBIOLOGY-SGM 2007; 153:29-41. [PMID: 17185532 DOI: 10.1099/mic.0.2006/000927-0] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The mechanisms by which pathogens sense and transport iron are important during infection, because of the low availability of free iron in the mammalian host. Iron is a key nutritional cue for the pathogen Cryptococcus neoformans, because it influences expression of the polysaccharide capsule that is the major virulence factor of the fungus. In this study, C. neoformans mutants were constructed with a defect in the iron-regulated gene SIT1 that encodes a putative siderophore iron transporter. Analysis of mutants in serotype A and D strains demonstrated that SIT1 is required for the use of siderophore-bound iron, and for growth in a low-iron environment. The sit1 mutants also showed changes in melanin formation and cell wall density, and it was found that mutants defective in protein kinase A, which is known to influence melanization and capsule formation, showed elevated SIT1 transcripts in both the serotype A and the serotype D backgrounds. Finally, the mutants were tested for virulence in a murine model of cryptococcosis, and it was found that SIT1 was not required for virulence. Overall, these studies establish links between iron acquisition, melanin formation and cAMP signalling in C. neoformans.
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Affiliation(s)
- Kristin L Tangen
- Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver BC V6T 1Z4, Canada
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Nosanchuk JD, Casadevall A. Impact of melanin on microbial virulence and clinical resistance to antimicrobial compounds. Antimicrob Agents Chemother 2006; 50:3519-28. [PMID: 17065617 PMCID: PMC1635213 DOI: 10.1128/aac.00545-06] [Citation(s) in RCA: 266] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Joshua D Nosanchuk
- Department of Medicine, Division of Infectious Diseases, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
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Martinez LR, Casadevall A. Specific antibody can prevent fungal biofilm formation and this effect correlates with protective efficacy. Infect Immun 2005; 73:6350-62. [PMID: 16177306 PMCID: PMC1230912 DOI: 10.1128/iai.73.10.6350-6362.2005] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
One of the most troublesome medical problems today is infection of prosthetic devices with organisms that form polysaccharide biofilms. This combined with increasing antimicrobial drug resistance is making many infectious diseases incurable. Cryptococcus neoformans is a human-pathogenic fungus that has a polysaccharide capsule and can form biofilms in prosthetic medical devices. We developed a system to study cryptococcal biofilm formation in vitro and studied the effect of antibody to the C. neoformans capsular polysaccharide on this process. C. neoformans biofilm formation was dependent on the presence of a polysaccharide capsule and correlated with the ability of capsular polysaccharide to bind the polystyrene solid support. Protective antibodies prevented biofilm formation whereas nonprotective antibodies were not effective. The mechanism of antibody action involved interference with capsular polysaccharide release from the fungal cell. In contrast, lactoferrin, an effector molecule of innate immune mechanisms, was unable to prevent fungal biofilm formation despite its efficacy against bacterial biofilms. Our results suggest a new role of adaptive humoral immunity whereby some antibodies can inhibit biofilm formation by encapsulated organisms. Vaccines that elicit antibody responses to capsular antigens and/or passive transfer of antibodies to microbial polysaccharides may be useful in preventing biofilm formation.
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Affiliation(s)
- Luis R Martinez
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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50
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Zarnowski R, Woods JP. Glutathione-dependent extracellular ferric reductase activities in dimorphic zoopathogenic fungi. MICROBIOLOGY-SGM 2005; 151:2233-2240. [PMID: 16000713 PMCID: PMC2748857 DOI: 10.1099/mic.0.27918-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In this study, extracellular glutathione-dependent ferric reductase (GSH-FeR) activities in different dimorphic zoopathogenic fungal species were characterized. Supernatants from Blastomyces dermatitidis, Histoplasma capsulatum, Paracoccidioides brasiliensis and Sporothrix schenckii strains grown in their yeast form were able to reduce iron enzymically with glutathione as a cofactor. Some variations in the level of reduction were noted amongst the strains. This activity was stable in acidic, neutral and slightly alkaline environments and was inhibited when trivalent aluminium and gallium ions were present. Using zymography, single bands of GSH-FeRs with apparent molecular masses varying from 430 to 460 kDa were identified in all strains. The same molecular mass range was determined by size exclusion chromatography. These data demonstrate that dimorphic zoopathogenic fungi produce and secrete a family of similar GSH-FeRs that may be involved in the acquisition and utilization of iron. Siderophore production by these and other fungi has sometimes been considered to provide a full explanation of iron acquisition in these organisms. Our work reveals an additional common mechanism that may be biologically and pathogenically important. Furthermore, while some characteristics of these enzymes such as extracellular location, cofactor utilization and large size are not individually unique, when considered together and shared across a range of fungi, they represent an important novel physiological feature.
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Affiliation(s)
- Robert Zarnowski
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, WI, USA
| | - Jon P Woods
- Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, WI, USA
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