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Aurongzeb M, Talha Malik HM, Jahanzaib M, Hassan SS, Rashid Y, Aziz T, Alharbi M. Exploring the extrachromosomal plasmid rDNA of Naegleria fowleri AY27 genotype II: A human brain-eating amoeba via high-throughput sequencing. BMC Med Genomics 2024; 17:125. [PMID: 38715056 PMCID: PMC11075319 DOI: 10.1186/s12920-024-01890-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 04/24/2024] [Indexed: 05/12/2024] Open
Abstract
Naegleria fowleri, also known as brain-earing amoeba, causes severe and rapidly fatal CNS infection in humans called primary amebic meningoencephalitis (PAM). The DNA from the N. fowleri clinical isolate was sequenced for circular extrachromosomal ribosomal DNA (CERE - rDNA). The CERE contains 18 S, 5.8 S, and 28 S ribosomal subunits separated by internal transcribed spacers, 5 open reading frames (ORFs), and mostly repeat elements comprising 7268 bp out of 15,786 bp (46%). A wide variety of variations and recombination events were observed. Finally, the ORFs that comprised only 4 hypothetical proteins were modeled and screened against Zinc drug-like compounds. Two compounds [ZINC77564275 (ethyl 2-(((4-isopropyl-4 H-1,2,4-triazol-3-yl) methyl) (methyl)amino) oxazole-4-carboxylate) and ZINC15022129 (5-(2-methoxyphenoxy)-[2,2'-bipyrimidine]-4,6(1 H,5 H)-dione)] were finalized as potential druggable compounds based on ADME toxicity analysis. We propose that the compounds showing the least toxicity would be potential drug candidates after laboratory experimental validation is performed.
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Affiliation(s)
- Muhammad Aurongzeb
- Department of Biotechnology, Faculty of Engineering Sciences & Technology, Hamdard University, Karachi, 74600, Pakistan
| | | | - Muhammad Jahanzaib
- JRC Genome Research, PCMD, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, 75270, Pakistan
| | - Syed Shah Hassan
- JRC Genome Research, PCMD, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, 75270, Pakistan
| | - Yasmeen Rashid
- Department of Biochemistry, University of Karachi, Karachi, 75270, Pakistan.
| | - Tariq Aziz
- Laboratory of Animal Health Food Hygiene and Quality, Department of Agriculture, University of Ioannina, Arta, 47132, Greece
| | - Metab Alharbi
- Department of Pharmacology and Toxicology College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
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Bhattacharya S. Episomal and chromosomal DNA replication and recombination in Entamoeba histolytica. Front Mol Biosci 2023; 10:1212082. [PMID: 37363402 PMCID: PMC10285105 DOI: 10.3389/fmolb.2023.1212082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 05/26/2023] [Indexed: 06/28/2023] Open
Abstract
Entamoeba histolytica is the causative agent of amoebiasis. DNA replication studies in E. histolytica first started with the ribosomal RNA genes located on episomal circles. Unlike most plasmids, Entamoeba histolytica rDNA circles lacked a fixed origin. Replication initiated from multiple sites on the episome, and these were preferentially used under different growth conditions. In synchronized cells the early origins mapped within the rDNA transcription unit, while at later times an origin in the promoter-proximal upstream intergenic spacer was activated. This is reminiscent of eukaryotic chromosomal replication where multiple potential origins are used. Biochemical studies on replication and recombination proteins in Entamoeba histolytica picked up momentum once the genome sequence was available. Sequence search revealed homologs of DNA replication and recombination proteins, including meiotic genes. The replicative DNA polymerases identified included the α, δ, ε of polymerase family B; lesion repair polymerases Rev1 and Rev3; a translesion repair polymerase of family A, and five families of polymerases related to family B2. Biochemical analysis of EhDNApolA confirmed its polymerase activity with expected kinetic constants. It could perform strand displacement, and translesion synthesis. The purified EhDNApolB2 had polymerase and exonuclease activities, and could efficiently bypass some types of DNA lesions. The single DNA ligase (EhDNAligI) was similar to eukaryotic DNA ligase I. It was a high-fidelity DNA ligase, likely involved in both replication and repair. Its interaction with EhPCNA was also demonstrated. The recombination-related proteins biochemically characterized were EhRad51 and EhDmc1. Both shared the canonical properties of a recombinase and could catalyse strand exchange over long DNA stretches. Presence of Dmc1 indicates the likelihood of meiosis in this parasite. Direct evidence of recombination in Entamoeba histolytica was provided by use of inverted repeat sequences located on plasmids or chromosomes. In response to a variety of stress conditions, and during encystation in Entamoeba invadens, recombination-related genes were upregulated and homologous recombination was enhanced. These data suggest that homologous recombination could have critical roles in trophozoite growth and stage conversion. Availability of biochemically characterized replication and recombination proteins is an important resource for exploration of novel anti-amoebic drug targets.
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Delafont V, Mercier A, Barrouilhet S, Mollichella ML, Herbelin P, Héchard Y. Identifying group-specific primers for environmental Heterolobosa by high-throughput sequencing. Microb Biotechnol 2022; 15:2476-2487. [PMID: 35920130 PMCID: PMC9437880 DOI: 10.1111/1751-7915.14080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 04/29/2022] [Accepted: 05/09/2022] [Indexed: 11/28/2022] Open
Abstract
Diversity of Heterolobosea (Excavata) in environments is poorly understood despite their ecological occurrence and health‐associated risk, partly because this group tends to be under‐covered by most universal eukaryotic primers used for sequencing. To overcome the limits of the traditional morpho‐taxonomy‐based biomonitoring, we constructed a primer database listing existing and newly designed specific primer pairs that have been evaluated for Heterolobosea 18S rRNA sequencing. In silico taxonomy performance against the current SILVA SSU database allowed the selection of primer pairs that were next evaluated on reference culture amoebal strains. Two primer pairs were retained for monitoring the diversity of Heterolobosea in freshwater environments, using high‐throughput sequencing. Results showed that one of the newly designed primer pairs allowed species‐level identification of most heterolobosean sequences. Such primer pair could enable informative, cultivation‐free assays for characterizing heterolobosean populations in various environments.
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Affiliation(s)
- Vincent Delafont
- Université de Poitiers, Laboratoire Ecologie et Biologie des Interactions, CNRS UMR 7267, 1 rue Georges Bonnet, TSA 51106, 86073, Poitiers Cedex 9, France
| | - Anne Mercier
- Université de Poitiers, Laboratoire Ecologie et Biologie des Interactions, CNRS UMR 7267, 1 rue Georges Bonnet, TSA 51106, 86073, Poitiers Cedex 9, France
| | - Stéphanie Barrouilhet
- EDF, Division Recherche et Développement, LNHE, 6 Quai Watier, 78401, Chatou, France
| | - Marie-Laure Mollichella
- Université de Poitiers, Laboratoire Ecologie et Biologie des Interactions, CNRS UMR 7267, 1 rue Georges Bonnet, TSA 51106, 86073, Poitiers Cedex 9, France
| | - Pascaline Herbelin
- EDF, Division Recherche et Développement, LNHE, 6 Quai Watier, 78401, Chatou, France
| | - Yann Héchard
- Université de Poitiers, Laboratoire Ecologie et Biologie des Interactions, CNRS UMR 7267, 1 rue Georges Bonnet, TSA 51106, 86073, Poitiers Cedex 9, France
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4
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The extrachromosomal elements of the Naegleria genus: How little we know. Plasmid 2021; 115:102567. [PMID: 33617907 DOI: 10.1016/j.plasmid.2021.102567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 02/05/2021] [Accepted: 02/10/2021] [Indexed: 11/20/2022]
Abstract
There are currently 47 characterized species in the Naegleria genus of free-living amoebae. Each amoeba has thousands of extrachromosomal elements that are closed circular structures comprised of a single ribosomal DNA (rDNA) copy and a large non-rDNA sequence. Despite the presence of putative open reading frames and introns, ribosomal RNA is the only established transcript. A single origin of DNA replication (ori) has been mapped within the non-rDNA sequence for one species (N. gruberi), a finding that strongly indicates that these episomes replicate independently of the cell's chromosomal DNA component. This article reviews that which has been published about these interesting DNA elements and by analyzing available sequence data, discusses the possibility that different phylogenetically related clusters of Naegleria species individually conserve ori structures and suggests where the rRNA promoter and termination sites may be located.
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Complete Genome Sequence of the Naegleria fowleri (Strain LEE) Closed Circular Extrachromosomal Ribosomal DNA Element. Microbiol Resour Announc 2020; 9:9/49/e01055-20. [PMID: 33272991 PMCID: PMC7714845 DOI: 10.1128/mra.01055-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The circular extrachromosomal ribosomal DNA (rDNA) element of Naegleria fowleri strain LEE was molecularly cloned and fully sequenced. The element comprises 15,786 bp and encodes a single copy of the organism’s rDNA cistron. The nonribosomal sequence contains five potential open reading frames, two large direct repeat sequences, and numerous smaller repeated-sequence regions. The circular extrachromosomal ribosomal DNA (rDNA) element of Naegleria fowleri strain LEE was molecularly cloned and fully sequenced. The element comprises 15,786 bp and contains a single copy of the organism’s rDNA cistron. The nonribosomal sequence contains five potential open reading frames, two large direct repeat sequences, and numerous smaller repeated-sequence regions.
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Samba-Louaka A, Delafont V, Rodier MH, Cateau E, Héchard Y. Free-living amoebae and squatters in the wild: ecological and molecular features. FEMS Microbiol Rev 2019; 43:415-434. [DOI: 10.1093/femsre/fuz011] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 04/30/2019] [Indexed: 02/06/2023] Open
Abstract
ABSTRACT
Free-living amoebae are protists frequently found in water and soils. They feed on other microorganisms, mainly bacteria, and digest them through phagocytosis. It is accepted that these amoebae play an important role in the microbial ecology of these environments. There is a renewed interest for the free-living amoebae since the discovery of pathogenic bacteria that can resist phagocytosis and of giant viruses, underlying that amoebae might play a role in the evolution of other microorganisms, including several human pathogens. Recent advances, using molecular methods, allow to bring together new information about free-living amoebae. This review aims to provide a comprehensive overview of the newly gathered insights into (1) the free-living amoeba diversity, assessed with molecular tools, (2) the gene functions described to decipher the biology of the amoebae and (3) their interactions with other microorganisms in the environment.
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Affiliation(s)
- Ascel Samba-Louaka
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
| | - Vincent Delafont
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
| | - Marie-Hélène Rodier
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
- Laboratoire de Parasitologie et Mycologie, CHU La Milétrie, 2 rue de la Milétrie, 86021 Poitiers Cedex, France
| | - Estelle Cateau
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
- Laboratoire de Parasitologie et Mycologie, CHU La Milétrie, 2 rue de la Milétrie, 86021 Poitiers Cedex, France
| | - Yann Héchard
- Laboratoire Ecologie et Biologie des Interactions (EBI), Equipe Microbiologie de l'Eau, Université de Poitiers, UMR CNRS 7267, 1 rue Georges Bonnet, TSA51106, 86073 POITIERS Cedex 9, France
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Mullican JC, Chapman NM, Tracy S. Mapping the Single Origin of Replication in the Naegleria gruberi Extrachromosomal DNA Element. Protist 2019; 170:141-152. [DOI: 10.1016/j.protis.2019.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 01/28/2019] [Accepted: 02/06/2019] [Indexed: 10/27/2022]
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Liechti N, Schürch N, Bruggmann R, Wittwer M. The genome of Naegleria lovaniensis, the basis for a comparative approach to unravel pathogenicity factors of the human pathogenic amoeba N. fowleri. BMC Genomics 2018; 19:654. [PMID: 30185166 PMCID: PMC6125883 DOI: 10.1186/s12864-018-4994-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 08/03/2018] [Indexed: 01/01/2023] Open
Abstract
Background Members of the genus Naegleria are free-living eukaryotes with the capability to transform from the amoeboid form into resting cysts or moving flagellates in response to environmental conditions. More than 40 species have been characterized, but only Naegleria fowleri (N. fowleri) is known as a human pathogen causing primary amoebic meningoencephalitis (PAM), a fast progressing and mostly fatal disease of the central nervous system. Several studies report an involvement of phospholipases and other molecular factors, but the mechanisms involved in pathogenesis are still poorly understood. To gain a better understanding of the relationships within the genus of Naegleria and to investigate pathogenicity factors of N. fowleri, we characterized the genome of its closest non-pathogenic relative N. lovaniensis. Results To gain insights into the taxonomy of Naegleria, we sequenced the genome of N. lovaniensis using long read sequencing technology. The assembly of the data resulted in a 30 Mb genome including the circular mitochondrial sequence. Unravelling the phylogenetic relationship using OrthoMCL protein clustering and maximum likelihood methods confirms the close relationship of N. lovaniensis and N. fowleri. To achieve an overview of the diversity of Naegleria proteins and to assess characteristics of the human pathogen N. fowleri, OrthoMCL protein clustering including data of N. fowleri, N. lovaniensis and N. gruberi was performed. GO enrichment analysis shows an association of N. fowleri specific proteins to the GO terms “Membrane” and “Protein Secretion.” Conclusion In this study, we characterize the hitherto unknown genome of N. lovaniensis. With the description of the 30 Mb genome, a further piece is added to reveal the complex taxonomic relationship of Naegleria. Further, the whole genome sequencing data confirms the hypothesis of the close relationship between N. fowleri and N. lovaniensis. Therefore, the genome of N. lovaniensis provides the basis for further comparative approaches on the molecular and genomic level to unravel pathogenicity factors of its closest human pathogenic relative N. fowleri and possible treatment options for the rare but mostly fatal primary meningoencephalitis. Electronic supplementary material The online version of this article (10.1186/s12864-018-4994-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Nicole Liechti
- Interfaculty Bioinformatics Unit, University of Bern, Bern, Switzerland.,Biology Division, Spiez Laboratory, Federal Office for Civil Protection, Austrasse, Spiez, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Nadia Schürch
- Biology Division, Spiez Laboratory, Federal Office for Civil Protection, Austrasse, Spiez, Switzerland
| | - Rémy Bruggmann
- Interfaculty Bioinformatics Unit, University of Bern, Bern, Switzerland
| | - Matthias Wittwer
- Biology Division, Spiez Laboratory, Federal Office for Civil Protection, Austrasse, Spiez, Switzerland.
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9
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Complete Genome Sequence of the Circular Extrachromosomal Element of Naegleria gruberi Strain EGB Ribosomal DNA. GENOME ANNOUNCEMENTS 2018; 6:6/6/e00020-18. [PMID: 29439032 PMCID: PMC5805870 DOI: 10.1128/genomea.00020-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The circular extrachromosomal element of Naegleria gruberi strain EGB was linearized, molecularly cloned, and fully sequenced. The sequence comprises 14,007 bp and encodes the organism’s rRNA genes, two potential open reading frames, and numerous repeated sequence regions.
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Waso M, Dobrowsky PH, Hamilton KA, Puzon G, Miller H, Khan W, Ahmed W. Abundance of Naegleria fowleri in roof-harvested rainwater tank samples from two continents. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:5700-5710. [PMID: 29230646 DOI: 10.1007/s11356-017-0870-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 11/28/2017] [Indexed: 05/24/2023]
Abstract
Roof-harvested rainwater (RHRW) has been used as an alternative source of water in water scarce regions of many countries. The microbiological and chemical quality of RHRW has been questioned due to the presence of bacterial and protozoan pathogens. However, information on the occurrence of pathogenic amoeba in RHRW tank samples is needed due to their health risk potential and known associations with opportunistic pathogens. Therefore, this study aims to determine the quantitative occurrence of Naegleria fowleri in RHRW tank samples from Southeast Queensland (SEQ), Australia (AU), and the Kleinmond Housing Scheme located in Kleinmond, South Africa (SA). In all, 134 and 80 RHRW tank samples were collected from SEQ, and the Kleinmond Housing Scheme, Western Cape, SA, respectively. Quantitative PCR (qPCR) assays were used to measure the concentrations of N. fowleri, and culture-based methods were used to measure fecal indicator bacteria (FIB) Escherichia coli (E. coli) and Enterococcus spp. Of the 134 tank water samples tested from AU, 69 and 62.7% were positive for E. coli, and Enterococcus spp., respectively. For the SA tank water samples, FIB analysis was conducted for samples SA-T41 to SA-T80 (n = 40). Of the 40 samples analyzed from SA, 95 and 35% were positive for E. coli and Enterococcus spp., respectively. Of the 134 water samples tested in AU, 15 (11.2%) water samples were positive for N. fowleri, and the concentrations ranged from 1.7 × 102 to 3.6 × 104 gene copies per 100 mL of water. Of the 80 SA tank water samples screened for N. fowleri, 15 (18.8%) tank water samples were positive for N. fowleri and the concentrations ranged from 2.1 × 101 to 7.8 × 104 gene copies per 100 mL of tank water. The prevalence of N. fowleri in RHRW tank samples from AU and SA thus warrants further development of dose-response models for N. fowleri and a quantitative microbial risk assessment (QMRA) to inform and prioritize strategies for reducing associated public health risks.
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Affiliation(s)
- Monique Waso
- Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa
| | - Penelope Heather Dobrowsky
- Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa
| | - Kerry Ann Hamilton
- Drexel University, 3141 Chestnut Street, Philadelphia, PA, 19104, USA
- CSIRO Land and Water, Ecosciences Precinct, 41 Boggo Road, Brisbane, QLD, 4102, Australia
| | - Geoffrey Puzon
- CSIRO Land and Water, Private Bag No.5, Wembley, WA, 6913, Australia
| | - Haylea Miller
- CSIRO Land and Water, Private Bag No.5, Wembley, WA, 6913, Australia
| | - Wesaal Khan
- Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa
| | - Warish Ahmed
- CSIRO Land and Water, Ecosciences Precinct, 41 Boggo Road, Brisbane, QLD, 4102, Australia.
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Siddiqui R, Ali IKM, Cope JR, Khan NA. Biology and pathogenesis of Naegleria fowleri. Acta Trop 2016; 164:375-394. [PMID: 27616699 DOI: 10.1016/j.actatropica.2016.09.009] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 09/06/2016] [Accepted: 09/06/2016] [Indexed: 12/13/2022]
Abstract
Naegleria fowleri is a protist pathogen that can cause lethal brain infection. Despite decades of research, the mortality rate related with primary amoebic meningoencephalitis owing to N. fowleri remains more than 90%. The amoebae pass through the nose to enter the central nervous system killing the host within days, making it one of the deadliest opportunistic parasites. Accordingly, we present an up to date review of the biology and pathogenesis of N. fowleri and discuss needs for future research against this fatal infection.
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12
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De Jonckheere JF. What do we know by now about the genus Naegleria? Exp Parasitol 2014; 145 Suppl:S2-9. [DOI: 10.1016/j.exppara.2014.07.011] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2013] [Revised: 07/07/2014] [Accepted: 07/22/2014] [Indexed: 10/24/2022]
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Abstract
In most organisms, the nuclear ribosomal RNA (rRNA) genes are highly repetitive and arranged as tandem repeats on one or more chromosomes. In Entamoeba, however, these genes are located almost exclusively on extrachromosomal circular DNA molecules with no clear evidence so far of a chromosomal copy. Such an uncommon location of rRNA genes may be a direct consequence of cellular physiology, as suggested by studies with Saccharomyces cerevisiae mutants in which the rDNA is extrachromosomal. In this review, Sudha Bhattacharya, Indrani Som and Alok Bhattacharya summarize current knowledge on the structural organization and replication of the Entamoeba rDNA plasmids. Other than the rRNAs encoded by these molecules, no protein-coding genes (including ribosomal protein genes) are found on any of them. They are unique among plasmids in that they do not initiate replication from a fixed origin but use multiple sites dispersed throughout the molecule. Further studies should establish the unique biochemical features of Entamoeba that lead to extrachromosomal rDNA.
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Affiliation(s)
- S Bhattacharya
- School of Environmental Sciences, Jawaharlal Nehru University, New Mehrauli Road, New Delhi 110067, India
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Walsh CJ. The structure of the mitotic spindle and nucleolus during mitosis in the amebo-flagellate Naegleria. PLoS One 2012; 7:e34763. [PMID: 22493714 PMCID: PMC3321029 DOI: 10.1371/journal.pone.0034763] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2011] [Accepted: 03/05/2012] [Indexed: 11/24/2022] Open
Abstract
Mitosis in the amebo-flagellate Naegleria pringsheimi is acentrosomal and closed (the nuclear membrane does not break down). The large central nucleolus, which occupies about 20% of the nuclear volume, persists throughout the cell cycle. At mitosis, the nucleolus divides and moves to the poles in association with the chromosomes. The structure of the mitotic spindle and its relationship to the nucleolus are unknown. To identify the origin and structure of the mitotic spindle, its relationship to the nucleolus and to further understand the influence of persistent nucleoli on cellular division in acentriolar organisms like Naegleria, three-dimensional reconstructions of the mitotic spindle and nucleolus were carried out using confocal microscopy. Monoclonal antibodies against three different nucleolar regions and α-tubulin were used to image the nucleolus and mitotic spindle. Microtubules were restricted to the nucleolus beginning with the earliest prophase spindle microtubules. Early spindle microtubules were seen as short rods on the surface of the nucleolus. Elongation of the spindle microtubules resulted in a rough cage of microtubules surrounding the nucleolus. At metaphase, the mitotic spindle formed a broad band completely embedded within the nucleolus. The nucleolus separated into two discreet masses connected by a dense band of microtubules as the spindle elongated. At telophase, the distal ends of the mitotic spindle were still completely embedded within the daughter nucleoli. Pixel by pixel comparison of tubulin and nucleolar protein fluorescence showed 70% or more of tubulin co-localized with nucleolar proteins by early prophase. These observations suggest a model in which specific nucleolar binding sites for microtubules allow mitotic spindle formation and attachment. The fact that a significant mass of nucleolar material precedes the chromosomes as the mitotic spindle elongates suggests that spindle elongation drives nucleolar division.
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Affiliation(s)
- Charles J Walsh
- Department of Biological Science, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
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The Naegleria genome: a free-living microbial eukaryote lends unique insights into core eukaryotic cell biology. Res Microbiol 2011; 162:607-18. [PMID: 21392573 DOI: 10.1016/j.resmic.2011.03.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Accepted: 01/29/2011] [Indexed: 11/24/2022]
Abstract
Naegleria gruberi, a free-living protist, has long been treasured as a model for basal body and flagellar assembly due to its ability to differentiate from crawling amoebae into swimming flagellates. The full genome sequence of Naegleria gruberi has recently been used to estimate gene families ancestral to all eukaryotes and to identify novel aspects of Naegleria biology, including likely facultative anaerobic metabolism, extensive signaling cascades, and evidence for sexuality. Distinctive features of the Naegleria genome and nuclear biology provide unique perspectives for comparative cell biology, including cell division, RNA processing and nucleolar assembly. We highlight here exciting new and novel aspects of Naegleria biology identified through genomic analysis.
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Fritz-Laylin LK, Prochnik SE, Ginger ML, Dacks JB, Carpenter ML, Field MC, Kuo A, Paredez A, Chapman J, Pham J, Shu S, Neupane R, Cipriano M, Mancuso J, Tu H, Salamov A, Lindquist E, Shapiro H, Lucas S, Grigoriev IV, Cande WZ, Fulton C, Rokhsar DS, Dawson SC. The genome of Naegleria gruberi illuminates early eukaryotic versatility. Cell 2010; 140:631-42. [PMID: 20211133 DOI: 10.1016/j.cell.2010.01.032] [Citation(s) in RCA: 341] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 11/17/2009] [Accepted: 01/15/2010] [Indexed: 12/18/2022]
Abstract
Genome sequences of diverse free-living protists are essential for understanding eukaryotic evolution and molecular and cell biology. The free-living amoeboflagellate Naegleria gruberi belongs to a varied and ubiquitous protist clade (Heterolobosea) that diverged from other eukaryotic lineages over a billion years ago. Analysis of the 15,727 protein-coding genes encoded by Naegleria's 41 Mb nuclear genome indicates a capacity for both aerobic respiration and anaerobic metabolism with concomitant hydrogen production, with fundamental implications for the evolution of organelle metabolism. The Naegleria genome facilitates substantially broader phylogenomic comparisons of free-living eukaryotes than previously possible, allowing us to identify thousands of genes likely present in the pan-eukaryotic ancestor, with 40% likely eukaryotic inventions. Moreover, we construct a comprehensive catalog of amoeboid-motility genes. The Naegleria genome, analyzed in the context of other protists, reveals a remarkably complex ancestral eukaryote with a rich repertoire of cytoskeletal, sexual, signaling, and metabolic modules.
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Affiliation(s)
- Lillian K Fritz-Laylin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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17
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Torres-Machorro AL, Hernández R, Cevallos AM, López-Villaseñor I. Ribosomal RNA genes in eukaryotic microorganisms: witnesses of phylogeny? FEMS Microbiol Rev 2010; 34:59-86. [DOI: 10.1111/j.1574-6976.2009.00196.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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18
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Maruyama S, Nozaki H. Sequence and Intranuclear Location of the Extrachromosomal rDNA Plasmid of the Amoebo-Flagellate Naegleria gruberi. J Eukaryot Microbiol 2007; 54:333-7. [PMID: 17669158 DOI: 10.1111/j.1550-7408.2007.00273.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Several lower eukaryotic genomes have distinctive organization of rDNA on extrachromosomal molecules: the rDNAs of the amoebo-flagellate Naegleria gruberi (Heterolobosea) are encoded on an extrachromosomal circular plasmid. Although the presence of a circular rDNA plasmid in N. gruberi has now been accepted, its sequence and intracellular location are still unclear. We have now sequenced the entire 14,128 bp of the extrachromosomal circular rDNA plasmid. It contains a single rRNA gene unit composed of 18S, 5.8S, and 28S rRNA genes, but no tRNA or 5S RNA genes. We predict that there are two open reading frames. The region that flanks the rRNA gene unit is A/T-rich, except for a highly G/C-rich region that is approximately 900 bp upstream of the rRNA genes. Fluorescence in situ hybridization of N. gruberi cells revealed that the rDNA plasmids cluster within the nucleolus, suggesting that they are highly organized for the efficient transcription of rRNAs. The N. gruberi rDNA plasmid has a unique high-order cluster structure that provides both a molecular basis for understanding chromosomal organization in basal eukaryotes, and a vehicle for constructing stable transgenic vectors.
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MESH Headings
- Animals
- DNA, Ribosomal/analysis
- DNA, Ribosomal/chemistry
- DNA, Ribosomal/genetics
- Genes, rRNA/genetics
- Naegleria/chemistry
- Naegleria/genetics
- Plasmids/genetics
- RNA, Ribosomal, 16S/analysis
- RNA, Ribosomal, 16S/genetics
- RNA, Ribosomal, 18S/analysis
- RNA, Ribosomal, 18S/genetics
- RNA, Ribosomal, 5.8S/analysis
- RNA, Ribosomal, 5.8S/genetics
- RNA, Ribosomal, 5S/analysis
- RNA, Ribosomal, 5S/genetics
- Sequence Analysis
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Affiliation(s)
- Shinichiro Maruyama
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
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19
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Wikmark OG, Einvik C, De Jonckheere JF, Johansen SD. Short-term sequence evolution and vertical inheritance of the Naegleria twin-ribozyme group I intron. BMC Evol Biol 2006; 6:39. [PMID: 16670006 PMCID: PMC1464144 DOI: 10.1186/1471-2148-6-39] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Accepted: 05/02/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Ribosomal DNA of several species of the free-living Naegleria amoeba harbors an optional group I intron within the nuclear small subunit ribosomal RNA gene. The intron (Nae.S516) has a complex organization of two ribozyme domains (NaGIR1 and NaGIR2) and a homing endonuclease gene (NaHEG). NaGIR2 is responsible for intron excision, exon ligation, and full-length intron RNA circularization, reactions typical for nuclear group I intron ribozymes. NaGIR1, however, is essential for NaHEG expression by generating the 5' end of the homing endonuclease messenger RNA. Interestingly, this unusual class of ribozyme adds a lariat-cap at the mRNA. RESULTS To elucidate the evolutionary history of the Nae.S516 twin-ribozyme introns we have analyzed 13 natural variants present in distinct Naegleria isolates. Structural variabilities were noted within both the ribozyme domains and provide strong comparative support to the intron secondary structure. One of the introns, present in N. martinezi NG872, contains hallmarks of a degenerated NaHEG. Phylogenetic analyses performed on separate data sets representing NaGIR1, NaGIR2, NaHEG, and ITS1-5.8S-ITS2 ribosomal DNA are consistent with an overall vertical inheritance pattern of the intron within the Naegleria genus. CONCLUSION The Nae.S516 twin-ribozyme intron was gained early in the Naegleria evolution with subsequent vertical inheritance. The intron was lost in the majority of isolates (70%), leaving a widespread but scattered distribution pattern. Why the apparent asexual Naegleria amoebae harbors active intron homing endonucleases, dependent on sexual reproduction for its function, remains a puzzle.
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Affiliation(s)
- Odd-Gunnar Wikmark
- Department of Molecular Biotechnology, RNA Research Group, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway
| | - Christer Einvik
- Department of Molecular Biotechnology, RNA Research Group, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway
- Department of Pediatrics, University Hospital of North Norway, N-9038 Tromsø, Norway
| | - Johan F De Jonckheere
- Protozoology Laboratory, Scientific Institute Public Health, B1050 Brussels, Belgium
| | - Steinar D Johansen
- Department of Molecular Biotechnology, RNA Research Group, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway
- Department of Fisheries and Natural Sciences, Bodø University College, N-8049 Bodø, Norway
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20
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Murtagh GJ, Dyer PS, Rogerson A, Nash GV, Laybourn-Parry J. A new species of Tetramitus in the benthos of a saline antarctic lake. Eur J Protistol 2002. [DOI: 10.1078/0932-4739-00836] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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21
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Trimbur GM, Goeckeler JL, Brodsky JL, Walsh CJ. Cloning, sequencing, and nucleolar targeting of the basal-body-binding nucleolar protein BN46/51. J Cell Sci 1999; 112 ( Pt 8):1159-68. [PMID: 10085251 DOI: 10.1242/jcs.112.8.1159] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
BN46/51 is an acidic protein found in the granular component of the nucleolus of the amebo-flagellate Naegleria gruberi. When Naegleria amebae differentiate into swimming flagellates, BN46/51 is found associated with the basal body complex at the base of the flagella. In order to determine the factors responsible for targeting BN46/51 to a specific subnucleolar region, cDNAs coding for both subunits were isolated and sequenced. Two clones, JG4.1 and JG12.1 representing the 46 kDa and 51 kDa subunits, respectively, were investigated in detail. JG12.1 encoded a polypeptide of 263 amino acids with a predicted size of 30.1 kDa that co-migrated with the 51 kDa subunit of BN46/51 when expressed in yeast. JG4.1 encoded a polypeptide of 249 amino acids with a predicted size of 28.8 kDa that co-migrated with the 46 kDa subunit of BN46/51. JG4.1 was identical to JG12.1 except for the addition of an aspartic acid between positions 94 and 95 of the JG12.1 sequence and the absence of 45 amino acids beginning at position 113. The predicted amino acid sequences were not closely related to any previously reported. However, the sequences did have 26–31% identity to a group of FKPBs (FK506 binding proteins) but lacked the peptidyl-prolyl cis-trans isomerase domain of the FKBPs. Both subunits contained two KKE and three KKX repeats found in other nucleolar proteins and in some microtubule binding proteins. Using ‘Far Western’ blots of nucleolar proteins, BN46/51 bound to polypeptides of 44 kDa and 74 kDa. The 44 kDa component was identified as the Naegleria homologue of fibrillarin. BN46/51 bound specifically to the nucleoli of fixed mammalian cells, cells which lack a BN46/51 related polypeptide. When the JG4.1 and JG12.1 cDNAs were expressed in yeast, each subunit was independently targeted to the yeast nucleolus. We conclude that BN46/51 represents a unique nucleolar protein that can form specific complexes with fibrillarin and other nucleolar proteins. We suggest that the association of BN46/51 with the MTOC of basal bodies may reflect its role in connecting the nucleolus with the MTOC activity for the mitotic spindle. This would provide a mechanism for nucleolar segregation during the closed mitosis of Naegleria amebae.
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MESH Headings
- 3T3 Cells
- Amino Acid Sequence
- Animals
- Antibodies, Monoclonal
- Base Sequence
- Blotting, Western
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cells, Cultured
- Chromosomal Proteins, Non-Histone/metabolism
- Cloning, Molecular
- Electrophoresis, Polyacrylamide Gel
- Flagella/metabolism
- Mice
- Microscopy, Fluorescence
- Molecular Sequence Data
- Naegleria/metabolism
- Nuclear Proteins/genetics
- Nuclear Proteins/metabolism
- Protein Binding
- RNA, Messenger/metabolism
- Saccharomyces cerevisiae
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Tacrolimus/chemistry
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Affiliation(s)
- G M Trimbur
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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22
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Einvik C, Elde M, Johansen S. Group I twintrons: genetic elements in myxomycete and schizopyrenid amoeboflagellate ribosomal DNAs. J Biotechnol 1998; 64:63-74. [PMID: 9823659 DOI: 10.1016/s0168-1656(98)00104-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Protists are unicellular eukaryotes which represent a significant fraction of the global biodiversity. The myxomycete Didymium and the schizopyrenid amoeboflagellate Naegleria are distantly related protists. However, we have noted several striking similarities in life cycle, cell morphology, and ribosomal DNA organization between these organisms. Both have multicopy nuclear extrachromosomal ribosomal DNAs. Here the small subunit ribosomal RNA genes are interrupted by an optional group I twintron, a novel category among the group I introns. Group I twintrons are mobile self-splicing introns of 1.3-1.4 kb in size, with a complex organization at the RNA level. A group I twintron consists of two distinct ribozymes (catalytic RNAs) with different functions in RNA processing, and an open reading frame encoding a functional homing endonuclease--all with prospects of application as molecular tools in biotechnology. Updated RNA secondary structure models of group I twintrons, as well as an example of in vitro ribozyme activity, are presented. We suggest that the group I twintrons have been independently established in myxomycetes and schizopyrenid amoeboflagellates by horizontal gene transfer due to a combination of the phagocytotic behavior in natural environments and the extrachromosomal multicopy nature of ribosomal DNA.
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Affiliation(s)
- C Einvik
- Department of Molecular Cell Biology, University of Tromsø, Norway
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23
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Inga R, De Doncker S, Gomez J, Lopez M, Garcia R, Le Ray D, Arevalo J, Dujardin JC. Relation between variation in copy number of ribosomal RNA encoding genes and size of harbouring chromosomes in Leishmania of subgenus Viannia. Mol Biochem Parasitol 1998; 92:219-28. [PMID: 9657327 DOI: 10.1016/s0166-6851(98)00009-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Chromosomal size polymorphism in Leishmania of subgenus Viannia has been correlated with eco-geography. The sizes of chromosomes bearing rDNA genes were determined in 69 isolates. A considerable size-variation was observed, ranging from 1100 to 1500 kb. Chromosomes of L.(V.). braziliensis, L.(V.)guyanensis and L.(V.) peruviana from northern Peru were significantly larger (200 kb) than those of L.(V.) peruviana from southern Peru. In addition, 31 out of 69 isolates presented each two different-sized homologues of the rDNA chromosome. Long range restriction mapping of three different-sized rDNA chromosomes from L.(V.)braziliensis M2903 and L.(V.)peruviana HB31 (north) and LC106 (south) each revealed three fragments delimited by PmeI restriction sites: two constant in size (the centre and one extremity of the chromosome) and one variable (the other extremity, containing a single cluster of rDNA genes). Further analysis of the M2903 rDNA chromosome allowed the localization of its 140 kb rDNA cluster at 85 kb from the telomeric end. Two arguments indicated that size-variation of the rDNA chromosome is partially due to amplification/deletion of the clustered rDNA genes: (i) size-variation of the cluster-containing fragment was proportional to the size-variation of the whole chromosome, and (ii) hybridization signal intensity of the rDNA chromosome with a small subunit rDNA probe strongly correlated with chromosomal size. Nevertheless, DNA sequences present between the rDNA cluster and the telomere might also play a role in chromosomal size polymorphism. In addition, our data suggest that rDNA gene copy number (20-40 copies cell(-1) under a diploid hypothesis) in subgenus Viannia is lower than reported previously.
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Affiliation(s)
- R Inga
- Department of Physiological Sciences and Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru
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24
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Kilvington S, Beeching J. Detection of a novel restriction fragment length polymorphism type in Naegleria fowleri (free-living amoeba) isolates from electricity power stations in England and France. Eur J Protistol 1997. [DOI: 10.1016/s0932-4739(97)80035-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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25
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Nierras CR, Liebman SW, Warner JR. DoesSaccharomyces need an organized nucleolus? Chromosoma 1997. [DOI: 10.1007/bf02510481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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26
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Bradley SG, Marciano-Cabral F. Diversity of free-living ‘naked’ amoeboid organisms. J Ind Microbiol Biotechnol 1996. [DOI: 10.1007/bf01574706] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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27
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Kilvington S, Beeching J. Identification and epidemiological typing of Naegleria fowleri with DNA probes. Appl Environ Microbiol 1995; 61:2071-8. [PMID: 7793928 PMCID: PMC167479 DOI: 10.1128/aem.61.6.2071-2078.1995] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Naegleria fowleri is a small free-living amoeboflagellate found in warm water habitats worldwide. The organism is pathogenic to humans, causing fatal primary amoebic meningoencephalitis. When monitoring the environment for the presence of N. fowleri, it is important to reliably differentiate the organism from other closely related but nonpathogenic species. To this end, we have developed species-specific DNA probes for use in the rapid identification of N. fowleri from the environment. Samples were taken from the thermal springs in Bath, England, and cultured for amoebae. Of 84 isolates of thermophilic Naegleria spp., 10 were identified as N. fowleri by probe hybridization. The identity of these isolates was subsequently confirmed by their specific whole-cell DNA restriction fragment length polymorphisms (RFLPs). One DNA clone was found to contain a repeated element that detected chromosomal RFLPs that were not directly visible on agarose gels. This enabled the further differentiation of strains within geographically defined whole-cell DNA RFLP groups. N. fowleri DNA probes represent a specific and potentially rapid method for the identification of the organism soon after primary isolation from the environment.
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Affiliation(s)
- S Kilvington
- Public Health Laboratory, Royal United Hospital, Bath, England
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28
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Dhar SK, Choudhury NR, Bhattacharaya A, Bhattacharya S. A multitude of circular DNAs exist in the nucleus of Entamoeba histolytica. Mol Biochem Parasitol 1995; 70:203-6. [PMID: 7637704 DOI: 10.1016/0166-6851(95)00008-o] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- S K Dhar
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India
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29
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Sehgal D, Mittal V, Ramachandran S, Dhar SK, Bhattacharya A, Bhattacharya S. Nucleotide sequence organisation and analysis of the nuclear ribosomal DNA circle of the protozoan parasite Entamoeba histolytica. Mol Biochem Parasitol 1994; 67:205-14. [PMID: 7870125 DOI: 10.1016/0166-6851(94)00129-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have sequenced the extrachromsomal ribosomal DNA (rDNA) circle of the human protozoan parasite Entamoeba histolytica HM-1:IMSS and present here the complete sequence organisation of the 24.5-kb molecule. Each circle contains two 5.9-kb rDNA transcription units organised as inverted repeats. The regions downstream (3543 bp) and upstream (9216 bp) of the rDNAs contain various families of short tandem repeats. Some of the upstream repeats share extensive sequence homology with the downstream repeats. In addition to the rDNAs themselves, the rDNA circle appears to code for only one other transcript which is 0.7 kb in size as seen in Northern blots. From DNA sequence analysis, no open reading frame could be assigned to the transcript. Extrachromosomal rDNA circles also exist in other E. histolytica strains. Restriction enzyme maps of rDNA circles were constructed from E. histolytica strains 200:NIH, HK-9 and Rahman; and Entamoeba moshkovskii strain Laredo. Striking differences were observed in the organisation of some of them, e.g. the HK-9, Rahman and Laredo circles contained only one rDNA unit and lacked the 0.7-kb transcript sequence. The short repeat sequences upstream and downstream of rDNAs were present in HK-9 and Rahman but absent in Laredo. Circles with one rDNA unit may be derived from those with two units by homologous recombination at direct repeat sequences located upstream and downstream of the two rDNAs.
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Affiliation(s)
- D Sehgal
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, Indiana
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30
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De Jonckheere JF. Comparison of partial SSUrDNA sequences suggests revisions of species names in the genus Naegleria. Eur J Protistol 1994. [DOI: 10.1016/s0932-4739(11)80080-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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31
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Hinkle G, Sogin ML. The evolution of the Vahlkampfiidae as deduced from 16S-like ribosomal RNA analysis. J Eukaryot Microbiol 1993; 40:599-603. [PMID: 8401474 DOI: 10.1111/j.1550-7408.1993.tb06114.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The amoebae, a phenotypically diverse, paraphyletic group of protists, have been largely neglected by molecular phylogeneticists. To better understand the evolution of amoebae, we sequenced and analyzed the 16S-like ribosomal RNA genes of three vahlkampfiid amoebae: Paratetramitus jugosus, Tetramitus rostratus and Vahlkampfia lobospinosa. The Vahlkampfiidae lineage is monophyletic, branches early along the eukaryotic line of descent, and is not a close relative of the multicellular amoebae that also reversibly transform from amoebae to flagellates.
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Affiliation(s)
- G Hinkle
- Center for Molecular Evolution, Marine Biological Laboratory, Woods Hole, Massachusetts 02543
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32
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33
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De Jonckheere JF. A group I intron in the SSUrDNA of some Naegleria spp. demonstrated by polymerase chain reaction amplification. J Eukaryot Microbiol 1993; 40:179-87. [PMID: 8461891 DOI: 10.1111/j.1550-7408.1993.tb04901.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The small subunit ribosomal DNA (SSUrDNA) of all described Naegleria spp. was amplified by polymerase chain reaction with universal primers. In all strains of N. andersoni andersoni, N. andersoni jamiesoni, N. australiensis italica and two related strains, and one out of four clusters of N. gruberi, a band of approximately 3.3 kb was obtained. All other strains displayed a band with the expected DNA length of 2.0 kb. This means the former have a 1.3 kb intron in the SSUrDNA. Restriction analysis demonstrated that the intron is between two conserved Pst I sites at the 5' end of the SSUrDNA. It also suggested the introns might not be identical in each species or subspecies. The Pst I fragment of SSUrDNA containing the 1.3 kb insert in N. andersoni andersoni was cloned and sequenced. The 1,296-nucleotide insert is situated in helix 19 of the SSUrDNA, which is an area of conserved primary and secondary structure. Sequence and secondary structure analyses of the insert revealed it it is a group I intron. This group I intron is very large and contains an open reading frame that could serve to encode a polypeptide of 139 amino acids in size.
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Affiliation(s)
- J F De Jonckheere
- Department of Microbiology, Institute of Hygiene and Epidemiology, Brussels, Belgium
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34
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Chakrabarti D, Dame JB, Gutell RR, Yowell CA. Characterization of the rDNA unit and sequence analysis of the small subunit rRNA and 5.8S rRNA genes from Tritrichomonas foetus. Mol Biochem Parasitol 1992; 52:75-83. [PMID: 1625709 DOI: 10.1016/0166-6851(92)90037-k] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The ribosomal RNA gene unit of the protozoan parasite Tritrichomonas foetus has been cloned and analyzed. Southern blot analysis of the genomic DNA showed that the ribosomal RNA gene unit is organized as a tandem head to tail repeat with a unit length of 6 kb. By Northern analysis a primary transcript of 5.8 kb was detected. Copy number analysis showed the presence of 12 copies of the ribosomal RNA gene unit. The lengths of the small subunit ribosomal RNA and 5.8S ribosomal RNA are 1571 bp and 159 bp, respectively, as determined by sequence analysis. The T. foetus small subunit ribosomal RNA sequence is one of the shortest eukaryotic small subunit rRNA sequences, similar in length to those from 2 other amitochondrial protists. Although shorter than the majority of the eukaryotic small subunit ribosomal RNAs, this sequence maintains the primary and secondary structure common to all eukaryotic small subunit ribosomal RNA structures, while truncating sequences found within the eukaryotic variable regions. The length of the large subunit ribosomal RNA was measured at 2.5 kb.
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Affiliation(s)
- D Chakrabarti
- Department of Infectious Diseases, College of Veterinary Medicine, University of Florida, Gainesville 32611
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35
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White MW, Shatry AM, Jutila MA, Speer CA. Biochemical and ultrastructural observations of coccidian parasite and host cell interactions. Subcell Biochem 1992; 18:365-83. [PMID: 1485357 DOI: 10.1007/978-1-4899-1651-8_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- M W White
- Veterinary Molecular Biology, Marsh Laboratory, Montana State University, Bozeman 59717
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36
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Schnare MN, Cook JR, Gray MW. Fourteen internal transcribed spacers in the circular ribosomal DNA of Euglena gracilis. J Mol Biol 1990; 215:85-91. [PMID: 2118961 DOI: 10.1016/s0022-2836(05)80097-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cytoplasmic ribosomes from Euglena gracilis contain 16 rRNA components. These include the typical 5 S, 5.8 S and 19 S rRNAs that are found in other eukaryotes as well as 13 discrete small RNAs that interact to form the equivalent of eukaryotic 25-28 S rRNA (accompanying paper). We have utilized DNA sequencing techniques to establish that genes for all of these RNAs, with the exception of 5 S rRNA, are encoded by the 11,500 base-pair circular rDNA of E. gracilis. We have determined the relative positions of the coding regions for the 19 S rRNA and the 14 components (including 5.8 S rRNA) of the large subunit rRNA, thereby establishing that the genes for each of these rRNAs are separated by internal transcribed spacers. We conclude that sequences corresponding to these spacers are removed post-transcriptionally from a high molecular weight pre-rRNA, resulting in a multiply fragmented large subunit rRNA. Internal transcribed spacers, in positions analogous to some of these additional Euglena rDNA spacers, have been found in the rDNA of other organisms and organelles. This finding supports the view that at least some internal transcribed spacers may have been present at an early stage in the evolution of rRNA genes.
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Affiliation(s)
- M N Schnare
- Department of Biochemistry, Dalhousie University Halifax, Nova Scotia, Canada
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37
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Clark CG, Lai EY, Fulton C, Cross GA. Electrophoretic karyotype and linkage groups of the amoeboflagellate Naegleria gruberi. THE JOURNAL OF PROTOZOOLOGY 1990; 37:400-8. [PMID: 2213653 DOI: 10.1111/j.1550-7408.1990.tb01164.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We have constructed a molecular karyotype for two strains of Naegleria gruberi using pulsed field gel electrophoresis. Each strain has about 23 chromosomes, considerably more than any previous estimate. These chromosomes range in size from 400 kilobasepairs to over 2,000 kilobasepairs. In Naegleria, construction of the DNA karyotype depends on assessment of the anomalous electrophoretic mobility of the circular ribosomal RNA genes. We have determined the chromosomal locations of an identified unique gene (flagellar calmodulin) and four identified multigene families (alpha- and beta-tubulin, actin, ubiquitin), as well as three differentially expressed genes of unknown functions. The ca. 12 actin genes are dispersed over at least seven chromosomes, whereas the majority of the more than eight alpha-tubulin genes are confined to a single chromosome. The ubiquitin genes are found on five chromosomes in one strain and seven in the other and the beta-tubulin genes are on three or four. Our observations provide a foundation for molecular genetic studies in this organism.
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Affiliation(s)
- C G Clark
- Laboratory of Molecular Parasitology, Rockefeller University, New York, New York 10021-6399
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38
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Abstract
In the 4 yr since the molecular biology of DNA in Naegleria was last reviewed several major advances have been made, and these are reviewed here: isolation and characterization of mitochondrial and ribosomal DNAs; enumeration of chromosomal DNAs by pulsed field gel electrophoresis; sequence analysis of differentially expressed genes; phylogenetic placement of the genus Naegleria among the eukaryotes and Naegleria species within the genus.
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Affiliation(s)
- C G Clark
- Laboratory of Molecular Parasitology, Rockefeller University, New York, New York 10021
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39
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Hughes JE, Welker DL. Copy number control and compatibility of nuclear plasmids in Dictyostelium discoideum. Plasmid 1989; 22:215-23. [PMID: 2633208 DOI: 10.1016/0147-619x(89)90004-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Copy number of the endogenous nuclear plasmids of Dictyostelium discoideum is a plasmid-specific trait. Copy number is stable over time, is constant relative to ploidy level, is independent of host cell genetic background, and is independent of the presence of a second unrelated plasmid in the same nucleus. Unrelated plasmids are compatible with one another within a single nucleus. Pairwise combinations of Ddp1, Ddp2, and Ddp5 were stably maintained over many generations in the absence of selection. In contrast, one of the D. discoideum plasmids (Ddp2) was incompatible with a recombinant plasmid derived from it (p7d2). In the absence of selection for retention of p7d2, transformants contain either one or the other but not both plasmids. The plasmids are stably maintained in host cells with differing genetic backgrounds, although plasmid-free colonies were detected at a frequency of about 1-2% in populations of some strains after 50 generations growth following a previous cloning.
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Affiliation(s)
- J E Hughes
- Department of Biology, Utah State University, Logan 84322-5500
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40
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Bhattacharya S, Bhattacharya A, Diamond LS, Soldo AT. Circular DNA of Entamoeba histolytica encodes ribosomal RNA. THE JOURNAL OF PROTOZOOLOGY 1989; 36:455-8. [PMID: 2553935 DOI: 10.1111/j.1550-7408.1989.tb01080.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The presence of repeated DNA sequences encoding RNA in Entamoeba histolytica has been reported. In the present study we demonstrate by agarose gel electrophoresis. DNase digestion and electron microscopic analysis that these genes are located on extrachromosomal circular DNA molecules with an approximate size of 26 kb. Detection of replication intermediates suggests the episomal nature of these molecules. Amplified, extrachromosomal rRNA genes appear to be a common feature among the lower eukaryotes, occurring more commonly as linear molecules and less commonly as circles. Entamoeba histolytica is 1 of the few organisms studied in which rRNA genes are located predominantly on extrachromosomal circles.
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MESH Headings
- Animals
- Blotting, Southern
- DNA Probes
- DNA Replication
- DNA, Circular/analysis
- DNA, Circular/genetics
- DNA, Circular/ultrastructure
- DNA, Ribosomal/analysis
- DNA, Ribosomal/genetics
- DNA, Ribosomal/ultrastructure
- Deoxyribonuclease I/metabolism
- Electrophoresis, Agar Gel
- Entamoeba histolytica/genetics
- Microscopy, Electron
- Nucleic Acid Hybridization
- RNA, Ribosomal/genetics
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Affiliation(s)
- S Bhattacharya
- Laboratory of Parasitic Diseases, NIAID, Bethesda, Maryland 20892
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41
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Clark CG, Cross GA, De Jonckheere JF. Evaluation of evolutionary divergence in the genus Naegleria by analysis of ribosomal DNA plasmid restriction patterns. Mol Biochem Parasitol 1989; 34:281-96. [PMID: 2733731 DOI: 10.1016/0166-6851(89)90057-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Ribosomal DNA (rDNA) plasmid restriction maps of 10 strains and rDNA hybridisation patterns of 61 additional strains have been used to assess inter- and intra-specific diversity and phylogenetic relationships in the genus Naegleria. The results obtained by this method largely confirm those of previous studies based on a variety of other criteria. They indicate that very little variation exists within the pathogenic species Naegleria fowleri despite its worldwide distribution and that it is closely related to the nonpathogenic Naegleria lovaniensis. Naegleria gruberi is most likely a polyphyletic grouping and care should be taken when using one strain as a reference point for this species. In addition, the two subspecies of the pathogenic Naegleria australiensis arose separately from within the range of variability encompassed by N. gruberi, as did the species Adelphamoeba galeacystis which should probably be assigned to the genus Naegleria. The species Naegleria jadini and Naegleria andersoni are not closely related to any other in the genus based on their rDNA patterns.
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Affiliation(s)
- C G Clark
- Laboratory of Molecular Parasitology, Rockefeller University, New York, NY 10021-6399
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42
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Huber M, Koller B, Gitler C, Mirelman D, Revel M, Rozenblatt S, Garfinkel L. Entamoeba histolytica ribosomal RNA genes are carried on palindromic circular DNA molecules. Mol Biochem Parasitol 1989; 32:285-96. [PMID: 2538748 DOI: 10.1016/0166-6851(89)90077-7] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Highly abundant DNA fragments obtained after restriction enzyme digests of nuclear DNA of Entamoeba histolytica strain HM-1:IMSS have been cloned and characterized. Northern blot hybridization to E. histolytica rRNA and sequence analysis identified the abundant DNAs as ribosomal DNA containing species. Several overlapping clones containing these abundant DNAs were isolated from 4 different genomic libraries of E. histolytica. Alignment of the restriction maps was consistent with a circular molecule, about 24.6 kilobase pairs (kb) in size. Nuclease BA131 digestion provided additional evidence for the circular nature of this DNA. The ribosomal DNA molecule contains two large inverted repeat-regions, each at least 5.2 kb in length. Sequence analysis of clone R715 revealed homology to the large rRNA units of various eukaryotic organisms. This clone was located in both inverted repeats, suggesting two rRNA cistrons per molecule. The inverted repeats are flanked by stretches of DNA which contain tandemly reiterated sequences. Southern blot analysis of E. histolytica nuclear DNA revealed the presence of two populations of molecules. These molecules have identical arrangements of restriction sites, but differ in size (0.7 kb) in a fragment containing tandemly reiterated sequences. Analysis of E. histolytica nuclear DNA by electron microscopy also revealed circular molecules. These molecules are about 26.6 kb +/- 0.5 kb in size and contain structural features predicted by the restriction map of the extrachromosomal ribosomal DNA of E. histolytica.
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Affiliation(s)
- M Huber
- Weizmann Institute of Science, Department of Biophysics, Rehovot, Israel
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43
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Abstract
All species and subspecies of the genus Naegleria were subjected to karyotype analysis by contour-clamped homogeneous electric field and transverse alternating-field electrophoresis. The former technique proved to be superior in detecting differences in karyotype. The chromosome pattern of each species and subspecies was found to be distinct. Between 15 and 23 bands were resolved, with chromosome sizes ranging from a few hundred kilobases to about 1.5 Mb. Hybridisation with cloned rDNA identified one band in all species, corresponding to the rDNA plasmid that does not migrate according to its molecular weight because it is circular. In Willaertia magna a similar size distribution was found, in contrast to Giardia and Entamoeba, which have only very large chromosomes. Within the pathogenic N. fowleri some strains showed slight differences in chromosome pattern. The karyotype differed more between strains within the subspecies N. and andersoni than between the two species N. fowleri and N. lovaniensis. The results suggest that karyotype analysis cannot be used to identify a Naegleria species but is useful for stock identification, gene localisation, genetic exchange studies and epidemiological investigation of the pathogenic N. fowleri.
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Affiliation(s)
- J F De Jonckheere
- Department of Microbiology, Instituut voor Hygiëne en Epidemiologie, Brussel, Belgium
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45
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White TC, Fase-Fowler F, van Luenen H, Calafat J, Borst P. The H circles of Leishmania tarentolae are a unique amplifiable system of oligomeric DNAs associated with drug resistance. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)37486-6] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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46
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47
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Clark CG, Cross GA. Circular ribosomal RNA genes are a general feature of schizopyrenid amoebae. THE JOURNAL OF PROTOZOOLOGY 1988; 35:326-9. [PMID: 2840492 DOI: 10.1111/j.1550-7408.1988.tb04352.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We have recently shown that the ribosomal RNA genes of the amoebo-flagellate Naegleria gruberi Schardinger, 1899, strain NEG-M are carried exclusively on a 14 kilobasepair plasmid. To explore the distribution of this unique gene arrangement, we have examined another strain of N. gruberi and four other species from the order Schizopyrenida. All have this unusual gene arrangement although the size of the plasmid varies widely. Species groups based on morphological criteria do not agree with those resulting from comparison of plasmid restriction enzyme patterns.
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Affiliation(s)
- C G Clark
- Laboratory of Molecular Parasitology, Rockefeller University, New York, New York 10021-6399
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48
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Affiliation(s)
- A B Futcher
- Department of Biochemistry, McMaster University, Hamilton, Ontario, Canada
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49
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Hughes JE, Ashtorab H, Welker DL. Nuclear plasmids in the Dictyostelium slime molds. DEVELOPMENTAL GENETICS 1988; 9:495-504. [PMID: 3243030 DOI: 10.1002/dvg.1020090426] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Cellular slime molds are one of only three types of eukaryotes known to contain circular nuclear plasmids. Unlike the 2-microns circle in Saccharomyces, different strains of Dictyostelium can carry different, nonhomologous plasmids. Covalently closed, circular DNA plasmids have been identified in D. discoideum, D. mucoroides, D. giganteum, and D. purpureum. These plasmids range in size from 1.3-27 kb and in copy number from 50-300 molecules per cell. Plasmids have been identified in approximately one-fifth of all isolates examined. The organization of their DNA in nucleosomes establishes their presence in the nucleus. We have successfully cotransformed endogenous Dictyostelium plasmids into D. discoideum using the G418 resistance shuttle vector B10S. Transformants carrying D. discoideum plasmids are recovered at much higher frequency than those carrying plasmids from the other Dictyostelium species. We have constructed recombinant plasmids based on the D. discoideum plasmid Ddp2 and the G418 resistance gene. With these extrachromosomal vectors, transformed cells are recovered at frequencies of up to 10(-4) per input cell, the vectors are stably maintained at high copy number in the absence of selection, and the vectors can be used to introduce foreign DNA sequences into D. discoideum cells.
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Affiliation(s)
- J E Hughes
- Dept. of Biology, Utah State University, Logan 84322-5500
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