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Lee SC, Corradi N, Doan S, Dietrich FS, Keeling PJ, Heitman J. Evolution of the sex-related locus and genomic features shared in microsporidia and fungi. PLoS One 2010; 5:e10539. [PMID: 20479876 PMCID: PMC2866331 DOI: 10.1371/journal.pone.0010539] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Accepted: 04/15/2010] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Microsporidia are obligate intracellular, eukaryotic pathogens that infect a wide range of animals from nematodes to humans, and in some cases, protists. The preponderance of evidence as to the origin of the microsporidia reveals a close relationship with the fungi, either within the kingdom or as a sister group to it. Recent phylogenetic studies and gene order analysis suggest that microsporidia share a particularly close evolutionary relationship with the zygomycetes. METHODOLOGY/PRINCIPAL FINDINGS Here we expanded this analysis and also examined a putative sex-locus for variability between microsporidian populations. Whole genome inspection reveals a unique syntenic gene pair (RPS9-RPL21) present in the vast majority of fungi and the microsporidians but not in other eukaryotic lineages. Two other unique gene fusions (glutamyl-prolyl tRNA synthetase and ubiquitin-ribosomal subunit S30) that are present in metazoans, choanoflagellates, and filasterean opisthokonts are unfused in the fungi and microsporidians. One locus previously found to be conserved in many microsporidian genomes is similar to the sex locus of zygomycetes in gene order and architecture. Both sex-related and sex loci harbor TPT, HMG, and RNA helicase genes forming a syntenic gene cluster. We sequenced and analyzed the sex-related locus in 11 different Encephalitozoon cuniculi isolates and the sibling species E. intestinalis (3 isolates) and E. hellem (1 isolate). There was no evidence for an idiomorphic sex-related locus in this Encephalitozoon species sample. According to sequence-based phylogenetic analyses, the TPT and RNA helicase genes flanking the HMG genes are paralogous rather than orthologous between zygomycetes and microsporidians. CONCLUSION/SIGNIFICANCE The unique genomic hallmarks between microsporidia and fungi are independent of sequence based phylogenetic comparisons and further contribute to define the borders of the fungal kingdom and support the classification of microsporidia as unusual derived fungi. And the sex/sex-related loci appear to have been subject to frequent gene conversion and translocations in microsporidia and zygomycetes.
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Affiliation(s)
- Soo Chan Lee
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Nicolas Corradi
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, Canada
| | - Sylvia Doan
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, Canada
| | - Fred S. Dietrich
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
- Institute for Genome Sciences and Policy, Duke University, Durham, North Carolina, United States of America
| | - Patrick J. Keeling
- Canadian Institute for Advanced Research, Department of Botany, University of British Columbia, Vancouver, Canada
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
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Southern TR, Jolly CE, Russell Hayman J. Augmentation of microsporidia adherence and host cell infection by divalent cations. FEMS Microbiol Lett 2006; 260:143-9. [PMID: 16842337 DOI: 10.1111/j.1574-6968.2006.00288.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The infection process of intracellular opportunistic microsporidia involves the forcible eversion of a coiled hollow polar filament that pierces the host cell membrane, allowing the passage of infectious sporoplasm into the host cell cytoplasm. Although the exact mechanism of spore activation leading to polar filament discharge is unknown, we have shown that spore adherence to host cells, which is mediated by sulfated glycosaminoglycans, may play a vital role. When adherence is inhibited, host cell infection decreases, indicating a direct link between adherence and infection. The goal of this study was to evaluate the effects of exogenous divalent cations on microsporidia spore adherence and infection. Data generated using an in vitro spore adherence assay show that spore adherence is augmented by manganese (Mn2+) and magnesium (Mg2+), but not by calcium (Ca2+). However, each of the three divalent cations contributed to increased host cell infection when included in the assay. Finally, we show that Mn2+ and Mg2+ may activate a constituent on the microsporidia spore, not on the host cell, leading to higher infection efficiency. This report further supports recent evidence that spore adherence to the host cell surface is an important aspect of the microsporidial infection process.
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Affiliation(s)
- Timothy R Southern
- Department of Microbiology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, USA
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Brosson D, Kuhn L, Delbac F, Garin J, P Vivarès C, Texier C. Proteomic analysis of the eukaryotic parasite Encephalitozoon cuniculi (microsporidia): a reference map for proteins expressed in late sporogonial stages. Proteomics 2006; 6:3625-35. [PMID: 16691553 DOI: 10.1002/pmic.200500796] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The microsporidian Encephalitozoon cuniculi is a unicellular obligate intracellular parasite considered as an emerging opportunistic human pathogen. The differentiation phase of its life cycle leads to the formation of stress-resistant spores. The E. cuniculi genome (2.9 Mbp) having been sequenced, we undertook a descriptive proteomic study of a spore-rich cell population isolated from culture supernatants. A combination of 2-DE and 2-DE-free techniques was applied to whole-cell protein extracts. Protein identification was performed using an automated MALDI-TOF-MS platform and a nanoLC-MS/MS instrument. A reference 2-DE map of about 350 major spots with multiple isoforms was obtained, and for the first time in microsporidia, a large set of unique proteins (177) including proteins with unknown function in a proportion of 25.6% was identified. The data are mainly discussed with reference to secretion and spore structural features, energy and carbohydrate metabolism, cell cycle control and parasite survival in the environment.
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Affiliation(s)
- Damien Brosson
- Equipe Parasitologie Moléculaire et Cellulaire, LBP, UMR CNRS 6023, Université Blaise Pascal, Aubière, France
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Taupin V, Méténier G, Vivarès CP, Prensier G. An improved procedure for Percoll gradient separation of sporogonial stages in Encephalitozoon cuniculi (Microsporidia). Parasitol Res 2006; 99:708-14. [PMID: 16738886 DOI: 10.1007/s00436-006-0231-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Accepted: 04/27/2006] [Indexed: 10/24/2022]
Abstract
Intracellular development of microsporidian parasites comprises a proliferative phase (merogony) followed by a differentiation phase (sporogony) leading to the release of resistant spores. Sporogony implies, successively, meront-to-sporont transformation, sporont division into sporoblasts, and sporogenesis. We report a procedure improving the separation of sporogonial stages of Encephalitozoon cuniculi, a species that develops inside parasitophorous vacuoles of mammalian cells. Supernatants of E. cuniculi-infected Madin-Darby canine kidney cell cultures provided a large number of parasites mixed with host-cell debris. This material was gently homogenized in phosphate-buffered saline containing 0.05% saponin and 0.05% Triton X-100 then filtered through glass wool columns. Centrifugation of the filtrate on 70% Percoll-0.23 M sucrose gradient gave a reproducible pattern of bands at different densities. Transmission electron microscopy showed that three of the four collected fractions were free of visible contaminants. Corresponding prominent cell stages were early sporoblasts (fraction B), late sporoblasts plus immature spores (fraction C), and mature spores (fraction D). Further centrifugation of the lightest fraction (A) on 30% Percoll-0.23 M sucrose gradient generated a sporont-rich fraction (A2). First analysis of proteins from fractions A2 and D by two-dimensional gel electrophoresis suggested a potential use of the described method for proteomic profiling.
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Affiliation(s)
- Vanessa Taupin
- Equipe Parasitologie Moléculaire et Cellulaire, LBP, UMR CNRS 6023, Université Blaise Pascal, 24 Avenue des Landais, 63177 Aubière Cedex, France
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5
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Chavant P, Taupin V, El Alaoui H, Wawrzyniak I, Chambon C, Prensier G, Méténier G, Vivarès CP. Proteolytic activity in Encephalitozoon cuniculi sporogonial stages: predominance of metallopeptidases including an aminopeptidase-P-like enzyme. Int J Parasitol 2005; 35:1425-33. [PMID: 16137693 DOI: 10.1016/j.ijpara.2005.05.009] [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] [Received: 03/08/2005] [Revised: 04/20/2005] [Accepted: 05/09/2005] [Indexed: 11/17/2022]
Abstract
A fraction enriched in spore precursor cells (sporoblasts) of the microsporidian Encephalitozoon cuniculi, an intracellular parasite of mammals, was obtained by Percoll gradient centrifugation. Soluble extracts of these cells exhibited proteolytic activity towards azocasein, with an alkaline optimum pH range (9-10). Prevalence of some metallopeptidases was supported by the stimulating effect of Ca2+, Mg2+, Mn2+ and Zn2+ ions, and inhibition by two chelating agents (EDTA and 1,10-phenanthroline), a thiol reductant (dithiothreitol) and two aminopeptidase inhibitors (bestatin and apstatin). Zymographic analysis revealed four caseinolytic bands at about 76, 70, 55 and 50 kDa. Mass spectrometry of tryptic peptides from one-dimensional gel slices identified a cytosol (leucine) aminopeptidase homologue (M17 family) in 50-kDa band and an enzyme similar to aminopeptidase P (AP-P) of cytosolic type (M24B subfamily) in 70-kDa band. Multiple sequence alignments showed conservation of critical residues for catalysis and metal binding. A long insertion in a common position was found in AP-P sequences from E. cuniculi and Nosema locustae, an insect-infecting microsporidian. The expression of cytosolic AP-P in sporogonial stages of microsporidia may suggest a key role in the attack of proline-containing peptides as a prerequisite to long-duration biosynthesis of structural proteins destined to the sporal polar tube.
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Affiliation(s)
- Patrick Chavant
- Parasitologie Moléculaire et Cellulaire, LBP, UMR-CNRS 6023, Université Blaise Pascal-Clermont 2, 63177 Aubière Cedex, France
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Abstract
Microsporidia are long-known parasitic organisms of almost every animal group, including invertebrates and vertebrates. Microsporidia emerged as important opportunistic pathogens in humans when AIDS became pandemic and, more recently, have also increasingly been detected in otherwise immunocompromised patients, including organ transplant recipients, and in immunocompetent persons with corneal infection or diarrhea. Two species causing rare infections in humans, Encephalitozoon cuniculi and Brachiola vesicularum, had previously been described from animal hosts (vertebrates and insects, respectively). However, several new microsporidial species, including Enterocytozoon bieneusi, the most prevalent human microsporidian causing human immunodeficiency virus-associated diarrhea, have been discovered in humans, raising the question of their natural origin. Vertebrate hosts are now identified for all four major microsporidial species infecting humans (E. bieneusi and the three Encephalitozoon spp.), implying a zoonotic nature of these parasites. Molecular studies have identified phenotypic and/or genetic variability within these species, indicating that they are not uniform, and have allowed the question of their zoonotic potential to be addressed. The focus of this review is the zoonotic potential of the various microsporidia and a brief update on other microsporidia which have no known host or an invertebrate host and which cause rare infections in humans.
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Affiliation(s)
- Alexander Mathis
- Institute of Parasitology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
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Kucerova Z, Moura H, Leitch GJ, Sriram R, Bern C, Kawai V, Vargas D, Gilman RH, Ticona E, Vivar A, Visvesvara GS. Purification of Enterocytozoon bieneusi spores from stool specimens by gradient and cell sorting techniques. J Clin Microbiol 2004; 42:3256-61. [PMID: 15243090 PMCID: PMC446316 DOI: 10.1128/jcm.42.7.3256-3261.2004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A three-step method for the purification of Enterocytozoon bieneusi spores from stool specimens was developed. The primary process of purification of the spores from bacterial contaminants involved Percoll gradient centrifugation followed by additional separation using cesium chloride density gradient centrifugation. The cesium chloride-isolated spores were further purified using a flow cytometer with cell sorting capabilities. Sorting was performed without the use of antibodies, fluorochromes, or dyes, leaving the sorted spores in their native state, which appears to be less destructive for spores. When quantified by flow cytometry using tubes with known numbers of highly fluorescent polystyrene beads, the sorted material showed a slight decrease in light scatter characteristics compared with the slightly larger Encephalitozoon species spores. Although the overall recovery of the E. bieneusi spores was low, calcofluor and Gram chromotrope staining, indirect immunofluorescence assay, and transmission electron microscopy revealed that the sorted material was highly purified and contained large numbers of E. bieneusi spores and relatively few bacteria and other debris. The sorted material appeared to be sufficiently pure and could be used for in vitro culture and for the development of a variety of diagnostic reagents as well as in studying the genome of E. bieneusi and host-parasite interactions.
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Affiliation(s)
- Zuzana Kucerova
- Department of Physiology, Morehouse School of Medicine, Atlanta, GA 30341, USA.
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Bacchi CJ, Rattendi D, Faciane E, Yarlett N, Weiss LM, Frydman B, Woster P, Wei B, Marton LJ, Wittner M. Polyamine metabolism in a member of the phylum Microspora (Encephalitozoon cuniculi): effects of polyamine analogues. MICROBIOLOGY (READING, ENGLAND) 2004; 150:1215-1224. [PMID: 15133083 PMCID: PMC3109667 DOI: 10.1099/mic.0.26889-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The uptake, biosynthesis and catabolism of polyamines in the microsporidian parasite Encephalitozoon cuniculi are detailed with reference to the effects of oligoamine and arylamine analogues of polyamines. Enc. cuniculi, an intracellular parasite of mammalian cells, has both biosynthetic and catabolic enzymes of polyamine metabolism, as demonstrated in cell-free extracts of mature spores. The uptake of polyamines was measured in immature, pre-emergent spores isolated from host cells by Percoll gradient. Spermine was rapidly taken up and metabolized to spermidine and an unknown, possibly acetamidopropanal, by spermidine/spermine N(1)-acetyltransferase (SSAT) and polyamine oxidase (PAO). Most of the spermidine and the unknown product were found in the cell incubation medium, indicating they were released from the cell. bis(Ethyl) oligoamine analogues of polyamines, such as SL-11144 and SL-11158, as well as arylamine analogues [BW-1, a bis(phenylbenzyl) 3-7-3 analogue] blocked uptake and interconversion of spermine at micromolar levels and, in the case of BW-1, acted as substrate for PAO. The Enc. cuniculi PAO activity differed from that found in mammalian cells with respect to pH optimum, substrate specificity and sensitivity to known PAO inhibitors. SL-11158 inhibited SSAT activity with a mixed type of inhibition in which the analogue had a 70-fold higher affinity for the enzyme than the natural substrate, spermine. The interest in Enc. cuniculi polyamine metabolism and the biochemical effects of these polyamine analogues is warranted since they cure model infections of Enc. cuniculi in mice and are potential candidates for human clinical trials.
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Affiliation(s)
- Cyrus J. Bacchi
- Haskins Laboratories and Department of Biology, Pace University, New York, NY 10038, USA
| | - Donna Rattendi
- Haskins Laboratories and Department of Biology, Pace University, New York, NY 10038, USA
| | - Evangeline Faciane
- Haskins Laboratories and Department of Biology, Pace University, New York, NY 10038, USA
| | - Nigel Yarlett
- Haskins Laboratories and Department of Biology, Pace University, New York, NY 10038, USA
- Haskins Laboratories and Department of Chemistry, Pace University, New York, NY 10038, USA
| | - Louis M. Weiss
- Departments of Medicine and Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | | | - Patrick Woster
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Benjamin Wei
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48202, USA
| | | | - Murray Wittner
- Departments of Medicine and Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Kucerova-Pospisilova Z, Moura H, Secor E, Visvesvara G. Immunoblot Analysis to Evaluate Serologic Reactivity of HIV-1-Negative Blood Donors to Microsporidia. J Eukaryot Microbiol 2003; 50 Suppl:577-8. [PMID: 14736169 DOI: 10.1111/j.1550-7408.2003.tb00636.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Moura H, Ospina M, Woolfitt AR, Barr JR, Visvesvara GS. Analysis of four human microsporidian isolates by MALDI-TOF mass spectrometry. J Eukaryot Microbiol 2003; 50:156-63. [PMID: 12836871 DOI: 10.1111/j.1550-7408.2003.tb00110.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Spores of four species of microsporidia isolated from humans were analyzed by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) and specific biomarkers were found for each. The microsporidia analyzed included three species, Encephalitozoon cuniculi, Encephalitozoon hellem, and Encephalitozoon intestinalis and the fourth organism is the recently described Brachiola algerae. Whole spores, spore shells, and soluble fractions were applied directly to the MALDI target without further purification steps. MALDI-TOF MS analysis of both whole spores and soluble fractions of the four isolates revealed a group of unique, characteristic, and reproducible spectral markers in the mass range of 2,000-8,000 Da. Statistical analysis of the averaged centroided masses uncovered two distinct sets of unique peptides or biomarkers, one originated from whole spores and the other from soluble fractions, that can differentiate the four microsporidian species studied. MALDI-TOF MS analysis of whole organisms is a rapid, sensitive, and specific option to characterize microsporidian isolates and has the potential for several applications in parasitology.
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Affiliation(s)
- Hercules Moura
- Atlanta Research and Education Foundation, Rio de Janeiro, Brazil.
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Hester JD, Varma M, Bobst AM, Ware MW, Lindquist HDA, Schaefer FW. Species-specific detection of three human-pathogenic microsporidial species from the genus Encephalitozoon via fluorogenic 5' nuclease PCR assays. Mol Cell Probes 2002; 16:435-44. [PMID: 12490145 DOI: 10.1006/mcpr.2002.0442] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study describes fluorogenic 5' nuclease PCR assays suitable for rapid, sensitive, high-throughput detection of the human-pathogenic microsporidial species Encephalitozoon hellem, E. cuniculi and E.intestinalis. The assays utilize species-specific primer sets and a genus-specific dual fluorescent-labeled probe that anneals to a region within the Encephalitozoon 16S rRNA gene. The assay design theoretically permits the probe to be used either with one set of primers for species-level determination or with a combination of all three primer sets for a genus-level screening of samples. The linear range of all three species-specific calibration curves that were developed using serial ten-fold dilutions of genomic DNA isolated from hemacytometer counted spores was determined to be between 10(4) and 10(-1) spores per PCR sample. The coefficients of variation were < or =5.2% over the entire 5-log span of each calibration curve. When DNA isolated from flow cytometric enumerated spores from each of the three Encephalitozoon species was used to evaluate the quantitative capability of the species' respective calibration curves, the results from 34 out of 36 (94%) samples were within 2 standard deviations. The species-specificity of each assay was confirmed using DNA isolated from 10(4) spores from each of the other two Encephalitozoon species as well as DNA extracted from numerous other protozoa, algae and bacteria.
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Affiliation(s)
- J D Hester
- National Exposure Research Laboratory, United States Environmental Protection Agency, Cincinnati, OH 45268, USA
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Bacchi CJ, Orozco D, Weiss LM, Frydman B, Valasinas A, Yarlett N, Marton LJ, Wittner M. SL-11158, a synthetic oligoamine, inhibits polyamine metabolism of Encephalitozoon cuniculi. J Eukaryot Microbiol 2002; Suppl:92S-94S. [PMID: 11906095 DOI: 10.1111/j.1550-7408.2001.tb00467.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- C J Bacchi
- Haskins Laboratories and Department of Biology, Pace University, New York, NY 10038, USA.
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Moura H, Visvesvara GS. A proteome approach to the host-parasite interaction of the microsporidian Encephalitozoon intestinalis. J Eukaryot Microbiol 2002; Suppl:56S-59S. [PMID: 11906079 DOI: 10.1111/j.1550-7408.2001.tb00452.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- H Moura
- Atlanta Research and Education Foundation, GA, USA.
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Kucerova-Pospisilova Z, Secor WE, Moura H, Desportes-Livage I, Datry A, Bern C, Leitch G, Visvesvara GS. An ELISA test to detect human serum antibodies reactive with Encephalitozoon intestinalis. J Eukaryot Microbiol 2002; Suppl:73S-74S. [PMID: 11906086 DOI: 10.1111/j.1550-7408.2001.tb00458.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Bacchi CJ, Lane S, Weiss LM, Yarlett N, Takvorian P, Cali A, Wittner M. Polyamine synthesis and interconversion by the Microsporidian Encephalitozoon cuniculi. J Eukaryot Microbiol 2001; 48:374-81. [PMID: 11411847 DOI: 10.1111/j.1550-7408.2001.tb00327.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Polyamines are small cationic molecules necessary for growth and differentiation in all cells. Although mammalian cells have been studied extensively, particularly as targets of polyamine antagonists, i.e. antitumor agents, polyamine metabolism has also been studied as a potential drug target in microorganisms. Since little is known concerning polyamine metabolism in the microsporidia, we investigated it in Encephalitozoon cuniculi, a microspordian associated with disseminated infections in humans. Organisms were grown in RK-13 cells and harvested using Percoll gradients. Electron microscopy indicated that the fractions banding at 1.051-1.059/g/ml in a microgradient procedure, and 1.102-1.119/g/ml in a scaled-up procedure were nearly homogenous, consisting of pre-emergent (immature) spores which showed large arrays of ribosomes near polar filament coils. Intact purified pre-emergent spores incubated with [1H] ornithine and methionine synthesized putrescine, spermidine, and spermine, while [14C]spermine was converted to spermidine and putrescine. Polyamine production from ornithine was inhibitable by DL-alpha-difluoromethylornithine (DFMO) but not by DL-alpha-difluoromethylarginine (DFMA). Cell-free extracts from mature spores released into the growth media had ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (AdoMetdc), and spermidine/spermine N1-acetyltransferase (SSAT) activities. ODC activity was inhibited by DFMO, but not by DFMA. AdoMetdc was putrescine-stimulated and inhibited by methylglyoxal-bis(guanylhydrazone); arginine decarboxylase activity could not be detected. It is apparent from these studies that Encephalitozoon cuniculi pre-emergent spores have a eukaryotic-type polyamine biosynthetic pathway and can interconvert exogenous polyamines. Pre-emergent spores were metabolically active with respect to polyamine synthesis and interconversion, while intact mature spores harvested from culture supernatants had little metabolic activity.
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Affiliation(s)
- C J Bacchi
- Haskins Laboratory, Pace University, New York, New York 10038, USA.
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