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Herbert H. Winkler - One of the best experts on this subject based on the ideXlab platform.
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The Rickettsia prowazekii ExoU homologue possesses phospholipase A1 (PLA1), PLA2, and lyso-PLA2 activities and can function in the absence of any eukaryotic
2016Co-Authors: Nicole A. Housley, Herbert H. Winkler, Jonathon P. AudiaAbstract:Here we have characterized the Rickettsia prowazekii RP534 protein, a homologue of the Pseudomonas aeruginosa ExoU phospholipase A (PLA) secreted cytotoxin. Our studies showed that purified recombinant RP534 PLA possessed the predicted PLA2 and lyso-PLA2 activities based on what has been published for P. aeruginosa ExoU. RP534 also displayed PLA1 activity under the conditions tested, whereas ExoU did not. In addition, recombinant RP534 displayed a basal PLA activity that could hydrolyze phosphatidylcholine in the absence of any eukaryotic cofactors. Interestingly, the addition of bovine liver superoxide dismutase 1 (SOD1), a known activator of P. aeruginosa ExoU, resulted in an increased rate of RP534-catalyzed phospholipid hydrolysis, indicating that mechanisms of activation of the ExoU family of PLAs may be evolutionarily conserved. The mechanism of SOD1-dependent stimulation of RP534 was further examined using active site mutants and a fluorogenic phospholipid substrate whose hydrolysis by RP534 over a short time course is measureable only in the presence of SOD1. These studies suggest a mechanism by which SOD1 stimulates RP534 activity once it has bound to the substrate. We also show that antibody raised against RP534 was useful for immunoprecipitating active RP534 from R. prowazekii lysed cell extracts, thus verifying that this protein is expressed and active in Rickettsiae isolated from embryonated hen egg yolk sacs. Rickettsia prowazekii is the etiological agent of epidemi
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INHIBITION OF THE GROWTH OF Rickettsia prowazekii IN CULTURED FIBROBLASTS BY LYMPHOKINES*
2013Co-Authors: Herbert H. WinklerAbstract:Epidemic typhus is an acute human disease caused by the obligate intracellular bacterium, Rickettsia prowazekii. R. prowazekii has a predilection for multiplication within the endothelial cells lining the capillaries (1) and an ability to multiply within the macrophages of the host (2). Thus cells that are not specially adapted for phagocytosis as well as professional phagocytes serve as sites of Rickettsial multiplication. Rickettsiae multiply freely in the cytoplasm of their host cells; they do not grow within vacuoles. The mechanisms of host defense against the etiological agents of epidemic typhus and other diseases caused by Rickettsia species are not clearly understood, but studies have indicated the importance of both humoral and cell-mediated immunity. The importance of specific antibody is suggested by the protective effect of the administration of immune serum in human cases of epidemic typhus (3). In addition, R. prowazekii treated with specific antiserum is destroyed within human monocytederived macrophages (4) and mouse macrophage-like cells (5). Specific antiserum also has been reported to inhibit the ability ofR. prowazekii to infect L929 mouse fibroblast
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Brief Definitive Report CLONED MOUSE INTERFERON-~, INHIBITS THE GROWTH OF Rickettsia prowazekii IN CULTURED MOUSE FIBROBLASTS*
2013Co-Authors: Herbert H. WinklerAbstract:The bacterium Rickettsia prowazekii is the etiological agent of epidemic typhus, a disease of humans in which Rickettsiae proliferate within the endothelial cells lining the capillaries. The Rickettsiae grow freely in the cytoplasm of their host cells; they are not enclosed within vacuoles. AntiRickettsial lymphokines may represent a mechanism of host defense against Rickettsiae present within nonprofessional phagocytes. Inhibition of the growth and survival of R. prowazekii in cultured mouse fibroblasts occurs when the fibroblasts are treated with lymphokines produced by antigen- or concanavalin A-stimulated mouse spleen cells (1). Rickettsial growth is also inhibited in cultured human fibroblasts, endothelial cells, and macrophages when these cells are treated with culture supernatants obtained from antigen- or lectin-stimulated human peripheral blood leukocytes (1, 2). Several characteristics of the antiRickettsial activity (ARA) in mouse lymphokines are consistent with the hypothesis that this activity is due to interferon-~, (IFN-~,) (1, 3). Like IFN- % ARA manifests species specificity or species preference, requires host cell protein synthesis for expression of activity, is relatively stable at 56°C, and is destroyed by exposure to pH 2, by trypsin, or by heating at 80°C. Furthermore, ARA is neutralized by antisera prepared against partially purified IFN-7 (3). In the present study, we present definitive evidence that IFN-~, has antiRickettsial activity: cloned mouse IFN-~, inhibits the growth of R. prowazekii in mouse L929 cells. Materials and Methods Cell Cultures. Mouse L929 cells were grown in Eagle's minimum essential medium supplemented with 10 % calf serum or 10 % fetal calf serum. Cultures of human foreskin fibroblasts were obtained from Mr. Frank Pindak, University of South Alabama, and were grown in Eagle's minimum essential medium supplemented with 10 % fetal calf serum. All cells were grown in a CO2 incubator at 34°C. Rickettsiae. Rickettsia prowazekii E strain was prepared from yolk sacs as previously described (1)
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DNA microarray analysis of the heat shock transcriptome of the obligate intracytoplasmic pathogen Rickettsia prowazekii.
Applied and environmental microbiology, 2008Co-Authors: Jonathon P. Audia, Mary C. Patton, Herbert H. WinklerAbstract:Here we present the first oligonucleotide DNA microarray analysis of global gene expression changes in the obligate intracytoplasmic pathogen Rickettsia prowazekii using temperature upshift as a model stress condition, and we describe a methodology for isolating highly purified Rickettsial RNA. In toto, 23 transcripts were significantly increased by temperature upshift (≥2.0-fold; P < 0.05), and no transcripts demonstrated reproducible decreases. Array results for three heat shock-inducible mRNAs were confirmed using quantitative reverse transcription-PCR.
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S-Adenosylmethionine Transport in Rickettsia prowazekii
Journal of bacteriology, 2003Co-Authors: Aimee M. Tucker, Herbert H. Winkler, Lonnie O. Driskell, David O. WoodAbstract:Rickettsia prowazekii, the causative agent of epidemic typhus, is an obligate, intracellular, parasitic bacterium that grows within the cytoplasm of eucaryotic host cells. Rickettsiae exploit this intracellular environment by using transport systems for the compounds available in the host cell's cytoplasm. Analysis of the R. prowazekii Madrid E genome sequence revealed the presence of a mutation in the Rickettsial metK gene, the gene encoding the enzyme responsible for the synthesis of S-adenosylmethionine (AdoMet). Since AdoMet is required for Rickettsial processes, the apparent inability of this strain to synthesize AdoMet suggested the presence of a Rickettsial AdoMet transporter. We have confirmed the presence of an AdoMet transporter in the Rickettsiae which, to our knowledge, is the first bacterial AdoMet transporter identified. The influx of AdoMet into Rickettsiae was a saturable process with a KT of 2.3 μM. Transport was inhibited by S-adenosylethionine and S-adenosylhomocysteine but not by sinfungin or methionine. Transport was also inhibited by 2,4-dinitrophenol, suggesting an energy-linked transport mechanism, and by N-ethylmaleimide. AdoMet transporters with similar properties were also identified in the Breinl strain of R. prowazekii and in Rickettsia typhi. By screening Escherichia coli clone banks for AdoMet transport, the R. prowazekii gene coding for a transporter, RP076 (sam), was identified. AdoMet transport in E. coli containing the R. prowazekii sam gene exhibited kinetics similar to that seen in Rickettsiae. The existence of a Rickettsial transporter for AdoMet raises intriguing questions concerning the evolutionary relationship between the synthesis and transport of this essential metabolite.
David O. Wood - One of the best experts on this subject based on the ideXlab platform.
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Establishment of a replicating plasmid in Rickettsia prowazekii.
PloS one, 2012Co-Authors: David O. Wood, Aimee M. Tucker, Andria Hines, Andrew Woodard, Lonnie O. Driskell, Nicole Y. Burkhardt, Timothy J. Kurtti, Gerald D. Baldridge, Ulrike G. MunderlohAbstract:Rickettsia prowazekii, the causative agent of epidemic typhus, grows only within the cytosol of eukaryotic host cells. This obligate intracellular lifestyle has restricted the genetic analysis of this pathogen and critical tools, such as replicating plasmid vectors, have not been developed for this species. Although replicating plasmids have not been reported in R. prowazekii, the existence of well-characterized plasmids in several less pathogenic Rickettsial species provides an opportunity to expand the genetic systems available for the study of this human pathogen. Competent R. prowazekii were transformed with pRAM18dRGA, a 10.3 kb vector derived from pRAM18 of R. amblyommii. A plasmid-containing population of R. prowazekii was obtained following growth under antibiotic selection, and the Rickettsial plasmid was maintained extrachromosomally throughout multiple passages. The transformant population exhibited a generation time comparable to that of the wild type strain with a copy number of approximately 1 plasmid per Rickettsia. These results demonstrate for the first time that a plasmid can be maintained in R. prowazekii, providing an important genetic tool for the study of this obligate intracellular pathogen.
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differential proteomic analysis of Rickettsia prowazekii propagated in diverse host backgrounds
Applied and Environmental Microbiology, 2011Co-Authors: Aimee M. Tucker, Lewis K. Pannell, Lonnie O. Driskell, David O. WoodAbstract:The obligate intracellular growth of Rickettsia prowazekii places severe restrictions on the analysis of Rickettsial gene expression. With a small genome, predicted to code for 835 proteins, identifying which proteins are differentially expressed in Rickettsiae that are isolated from different hosts or that vary in virulence is critical to an understanding of Rickettsial pathogenicity. We employed a liquid chromatography (LC)-linear trap quadrupole (LTQ)-Orbitrap mass spectrometer for simultaneous acquisition of quantitative mass spectrometry (MS)-only data and tandem mass spectrometry (MS-MS) sequence data. With the use of a combination of commercially available algorithms and in-house software, quantitative MS-only data and comprehensive peptide coverage generated from MS-MS were integrated, resulting in the assignment of peptide identities with intensity values, allowing for the differential comparison of complex protein samples. With the use of these protocols, it was possible to directly compare protein abundance and analyze changes in the total proteome profile of R. prowazekii grown in different host backgrounds. Total protein extracted from Rickettsiae grown in murine, tick, and insect cell lines or hen egg yolk sacs was analyzed. Here, we report the fold changes, including an upregulation of shock-related proteins, in Rickettsiae cultivated in tissue culture compared to the level for Rickettsiae harvested from hen yolk sacs. The ability to directly compare, in a complex sample, differential Rickettsial protein expression provides a snapshot of host-specific proteomic profiles that will help to identify proteins important in intracellular growth and virulence.
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Analysis of convergent gene transcripts in the obligate intracellular bacterium Rickettsia prowazekii.
PloS one, 2011Co-Authors: Andrew Woodard, David O. WoodAbstract:Termination of transcription is an important component of bacterial gene expression. However, little is known concerning this process in the obligate intracellular pathogen and model for reductive evolution, Rickettsia prowazekii. To assess transcriptional termination in this bacterium, transcripts of convergent gene pairs, some containing predicted intrinsic terminators, were analyzed. These analyses revealed that, rather than terminating at a specific site within the intervening region between the convergent genes, most of the transcripts demonstrated either a lack of termination within this region, which generated antisense RNA, or a putative non-site-specific termination that occurred throughout the intervening sequence. Transcripts terminating at predicted intrinsic terminators, as well as at a putative Rho-dependant terminator, were also examined and found to vary based on the Rickettsial host environment. These results suggest that transcriptional termination, or lack thereof, plays a role in Rickettsial gene regulation.
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directed mutagenesis of the Rickettsia prowazekii pld gene encoding phospholipase d
Infection and Immunity, 2009Co-Authors: Lonnie O. Driskell, David H. Walker, Aimee M. Tucker, Vsevolod L. Popov, Lihong Zhang, Yan Liu, David O. WoodAbstract:Rickettsia prowazekii, the causative agent of epidemic typhus, is an obligately intracytoplasmic bacterium, a lifestyle that imposes significant barriers to genetic manipulation. The key to understanding how this unique bacterium evades host immunity is the mutagenesis of selected genes hypothesized to be involved in virulence. The R. prowazekii pld gene, encoding a protein with phospholipase D activity, has been associated with phagosomal escape. To demonstrate the feasibility of site-directed knockout mutagenesis of Rickettsial genes and to generate a nonrevertible vaccine strain, we utilized homologous recombination to generate a pld mutant of the virulent R. prowazekii strain Madrid Evir. Using linear DNA for transformation, a double-crossover event resulted in the replacement of the Rickettsial wild-type gene with a partially deleted pld gene. Linear DNA was used to prevent potentially revertible single-crossover events resulting in plasmid insertion. Southern blot and PCR analyses were used to confirm the presence of the desired mutation and to demonstrate clonality. While no phenotypic differences were observed between the mutant and wild-type strains when grown in tissue culture, the pld mutant exhibited attenuated virulence in the guinea pig model. In addition, animals immunized with the mutant strain were protected against subsequent challenge with the virulent Breinl strain, suggesting that this transformant could serve as a nonrevertible, attenuated vaccine strain. This study demonstrates the feasibility of generating site-directed Rickettsial gene mutants, providing a new tool for understanding Rickettsial biology and furthering advances in the prevention of epidemic typhus.
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Mariner-based transposon mutagenesis of Rickettsia prowazekii.
Applied and environmental microbiology, 2007Co-Authors: Zhi-mei Liu, Lonnie O. Driskell, Aimee M. Tucker, David O. WoodAbstract:Rickettsia prowazekii, the causative agent of epidemic typhus, is an obligate intracellular bacterium that grows directly within the cytoplasm of its host cell, unbounded by a vacuolar membrane. The obligate intracytoplasmic nature of Rickettsial growth places severe restrictions on the genetic analysis of this distinctive human pathogen. In order to expand the repertoire of genetic tools available for the study of this pathogen, we have employed the versatile mariner-based, Himar1 transposon system to generate insertional mutants of R. prowazekii. A transposon containing the R. prowazekii arr-2 rifampin resistance gene and a gene coding for a green fluorescent protein (GFP(UV)) was constructed and placed on a plasmid expressing the Himar1 transposase. Electroporation of this plasmid into R. prowazekii resulted in numerous transpositions into the Rickettsial genome. Transposon insertion sites were identified by rescue cloning, followed by DNA sequencing. Random transpositions integrating at TA sites in both gene coding and intergenic regions were identified. Individual Rickettsial clones were isolated by the limiting-dilution technique. Using both fixed and live-cell techniques, R. prowazekii transformants expressing GFP(UV) were easily visible by fluorescence microscopy. Thus, a mariner-based system provides an additional mechanism for generating Rickettsial mutants that can be screened using GFP(UV) fluorescence.
Aimee M. Tucker - One of the best experts on this subject based on the ideXlab platform.
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Establishment of a replicating plasmid in Rickettsia prowazekii.
PloS one, 2012Co-Authors: David O. Wood, Aimee M. Tucker, Andria Hines, Andrew Woodard, Lonnie O. Driskell, Nicole Y. Burkhardt, Timothy J. Kurtti, Gerald D. Baldridge, Ulrike G. MunderlohAbstract:Rickettsia prowazekii, the causative agent of epidemic typhus, grows only within the cytosol of eukaryotic host cells. This obligate intracellular lifestyle has restricted the genetic analysis of this pathogen and critical tools, such as replicating plasmid vectors, have not been developed for this species. Although replicating plasmids have not been reported in R. prowazekii, the existence of well-characterized plasmids in several less pathogenic Rickettsial species provides an opportunity to expand the genetic systems available for the study of this human pathogen. Competent R. prowazekii were transformed with pRAM18dRGA, a 10.3 kb vector derived from pRAM18 of R. amblyommii. A plasmid-containing population of R. prowazekii was obtained following growth under antibiotic selection, and the Rickettsial plasmid was maintained extrachromosomally throughout multiple passages. The transformant population exhibited a generation time comparable to that of the wild type strain with a copy number of approximately 1 plasmid per Rickettsia. These results demonstrate for the first time that a plasmid can be maintained in R. prowazekii, providing an important genetic tool for the study of this obligate intracellular pathogen.
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differential proteomic analysis of Rickettsia prowazekii propagated in diverse host backgrounds
Applied and Environmental Microbiology, 2011Co-Authors: Aimee M. Tucker, Lewis K. Pannell, Lonnie O. Driskell, David O. WoodAbstract:The obligate intracellular growth of Rickettsia prowazekii places severe restrictions on the analysis of Rickettsial gene expression. With a small genome, predicted to code for 835 proteins, identifying which proteins are differentially expressed in Rickettsiae that are isolated from different hosts or that vary in virulence is critical to an understanding of Rickettsial pathogenicity. We employed a liquid chromatography (LC)-linear trap quadrupole (LTQ)-Orbitrap mass spectrometer for simultaneous acquisition of quantitative mass spectrometry (MS)-only data and tandem mass spectrometry (MS-MS) sequence data. With the use of a combination of commercially available algorithms and in-house software, quantitative MS-only data and comprehensive peptide coverage generated from MS-MS were integrated, resulting in the assignment of peptide identities with intensity values, allowing for the differential comparison of complex protein samples. With the use of these protocols, it was possible to directly compare protein abundance and analyze changes in the total proteome profile of R. prowazekii grown in different host backgrounds. Total protein extracted from Rickettsiae grown in murine, tick, and insect cell lines or hen egg yolk sacs was analyzed. Here, we report the fold changes, including an upregulation of shock-related proteins, in Rickettsiae cultivated in tissue culture compared to the level for Rickettsiae harvested from hen yolk sacs. The ability to directly compare, in a complex sample, differential Rickettsial protein expression provides a snapshot of host-specific proteomic profiles that will help to identify proteins important in intracellular growth and virulence.
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directed mutagenesis of the Rickettsia prowazekii pld gene encoding phospholipase d
Infection and Immunity, 2009Co-Authors: Lonnie O. Driskell, David H. Walker, Aimee M. Tucker, Vsevolod L. Popov, Lihong Zhang, Yan Liu, David O. WoodAbstract:Rickettsia prowazekii, the causative agent of epidemic typhus, is an obligately intracytoplasmic bacterium, a lifestyle that imposes significant barriers to genetic manipulation. The key to understanding how this unique bacterium evades host immunity is the mutagenesis of selected genes hypothesized to be involved in virulence. The R. prowazekii pld gene, encoding a protein with phospholipase D activity, has been associated with phagosomal escape. To demonstrate the feasibility of site-directed knockout mutagenesis of Rickettsial genes and to generate a nonrevertible vaccine strain, we utilized homologous recombination to generate a pld mutant of the virulent R. prowazekii strain Madrid Evir. Using linear DNA for transformation, a double-crossover event resulted in the replacement of the Rickettsial wild-type gene with a partially deleted pld gene. Linear DNA was used to prevent potentially revertible single-crossover events resulting in plasmid insertion. Southern blot and PCR analyses were used to confirm the presence of the desired mutation and to demonstrate clonality. While no phenotypic differences were observed between the mutant and wild-type strains when grown in tissue culture, the pld mutant exhibited attenuated virulence in the guinea pig model. In addition, animals immunized with the mutant strain were protected against subsequent challenge with the virulent Breinl strain, suggesting that this transformant could serve as a nonrevertible, attenuated vaccine strain. This study demonstrates the feasibility of generating site-directed Rickettsial gene mutants, providing a new tool for understanding Rickettsial biology and furthering advances in the prevention of epidemic typhus.
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Mariner-based transposon mutagenesis of Rickettsia prowazekii.
Applied and environmental microbiology, 2007Co-Authors: Zhi-mei Liu, Lonnie O. Driskell, Aimee M. Tucker, David O. WoodAbstract:Rickettsia prowazekii, the causative agent of epidemic typhus, is an obligate intracellular bacterium that grows directly within the cytoplasm of its host cell, unbounded by a vacuolar membrane. The obligate intracytoplasmic nature of Rickettsial growth places severe restrictions on the genetic analysis of this distinctive human pathogen. In order to expand the repertoire of genetic tools available for the study of this pathogen, we have employed the versatile mariner-based, Himar1 transposon system to generate insertional mutants of R. prowazekii. A transposon containing the R. prowazekii arr-2 rifampin resistance gene and a gene coding for a green fluorescent protein (GFP(UV)) was constructed and placed on a plasmid expressing the Himar1 transposase. Electroporation of this plasmid into R. prowazekii resulted in numerous transpositions into the Rickettsial genome. Transposon insertion sites were identified by rescue cloning, followed by DNA sequencing. Random transpositions integrating at TA sites in both gene coding and intergenic regions were identified. Individual Rickettsial clones were isolated by the limiting-dilution technique. Using both fixed and live-cell techniques, R. prowazekii transformants expressing GFP(UV) were easily visible by fluorescence microscopy. Thus, a mariner-based system provides an additional mechanism for generating Rickettsial mutants that can be screened using GFP(UV) fluorescence.
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Dissecting the Rickettsia prowazekii genome: genetic and proteomic approaches.
Annals of the New York Academy of Sciences, 2005Co-Authors: Aimee M. Tucker, Lewis K. Pannell, David O. WoodAbstract:The obligate nature of Rickettsia prowazekii intracellular growth places severe restrictions on the analysis of Rickettsial gene function and gene expression. Fortunately, this situation is improving as methods for the genetic manipulation and proteomic analysis of this fascinating human pathogen become available. In this paper, we review the current status of Rickettsial genetics and the isolation of Rickettsial mutants using a genetic approach. In addition, the examination of Rickettsial gene expression through characterization of the Rickettsial proteome will be described. This will include a description of a high-throughput, accurate mass approach that has identified 596 Rickettsial proteins in a complex Rickettsial protein sample.
Charles G. Kurland - One of the best experts on this subject based on the ideXlab platform.
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The genome sequence of Rickettsia prowazekii and the origin of mitochondria
Nature, 1998Co-Authors: Siv G. E. Andersson, Herbert H. Winkler, Alireza Zomorodipour, Jan Andersson, Thomas Sicheritz-pontén, U. Cecilia M. Alsmark, Raf M. Podowski, A. Kristina Näslund, Ann-sofie Eriksson, Charles G. KurlandAbstract:We describe here the complete genome sequence (1,111,523 base pairs) of the obligate intracellular parasite Rickettsia prowazekii, the causative agent of epidemic typhus. This genome contains 834 p ...
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The genome sequence of Rickettsia prowazekii and the origin of mitochondria
Nature, 1998Co-Authors: Siv G. E. Andersson, Herbert H. Winkler, Alireza Zomorodipour, Thomas Sicheritz-pontén, U. Cecilia M. Alsmark, Raf M. Podowski, A. Kristina Näslund, Ann-sofie Eriksson, Jan O. Andersson, Charles G. KurlandAbstract:We describe here the complete genome sequence (1,111,523 base pairs) of the obligate intracellular parasite Rickettsia prowazekii , the causative agent of epidemic typhus. This genome contains 834 protein-coding genes. The functional profiles of these genes show similarities to those of mitochondrial genes: no genes required for anaerobic glycolysis are found in either R. prowazekii or mitochondrial genomes, but a complete set of genes encoding components of the tricarboxylic acid cycle and the respiratory-chain complex is found in R. prowazekii . In effect, ATP production in Rickettsia is the same as that in mitochondria. Many genes involved in the biosynthesis and regulation of biosynthesis of amino acids and nucleosides in free-living bacteria are absent from R. prowazekii and mitochondria. Such genes seem to have been replaced by homologues in the nuclear (host) genome. The R. prowazekii genome contains the highest proportion of non-coding DNA (24%) detected so far in a microbial genome. Such non-coding sequences may be degraded remnants of ‘neutralized’ genes that await elimination from the genome. Phylogenetic analyses indicate that R. prowazekii is more closely related to mitochondria than is any other microbe studied so far.
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The Rickettsia prowazekii Genome: A Random Sequence Analysis
Microbial & comparative genomics, 1996Co-Authors: Siv G. E. Andersson, A. Kristina Näslund, Ann-sofie Eriksson, Morten S. Andersen, Charles G. KurlandAbstract:We describe here the first general survey of the genomic content and the coding capacity of the 1.1 Mb genome of Rickettsia prowazekii based on an analysis of a total of 200 kb of unique sequence data collected in a random manner. Based on nucleotide distribution profiles, we estimate that the R. prowazekii genome may have a coding density of 60%-70% and that it may contain a total of circa 800 genes. Here, we have tentatively identified and classified 173 of these genes. Our analysis suggests that the R. prowazekii genome is a highly derived, reduced genome that has lost many genes involved in amino acid biosynthetic pathways and regulatory functions. Furthermore, the R. prowazekii genome seems to lack glycolytic genes, but it does contain genes encoding components of the tricarboxylic acid cycle as well as of the electron transport system. We have also encountered a family of homologous genes coding for ATP/ADP translocases, as observed in several mitochondrial genomes. We relate these findings to previ...
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A chimeric disposition of the elongation factor genes in Rickettsia prowazekii.
Journal of bacteriology, 1996Co-Authors: Ann-christine Syvänen, Siv G. E. Andersson, Haleh Amiri, Asfar Jamal, Charles G. KurlandAbstract:An exceptional disposition of the elongation factor genes is observed in Rickettsia prowazekii, in which there is only one tuf gene, which is distant from the lone fus gene. In contrast, the closely related bacterium Agrobacterium tumefaciens has the normal bacterial arrangement of two tuf genes, of which one is tightly linked to the fus gene. Analysis of the flanking sequences of the single tuf gene in R. prowazekii shows that it is preceded by two of the four tRNA genes located in the 5' region of the Escherichia coli tufB gene and that it is followed by rpsJ as well as associated ribosomal protein genes, which in E. coli are located downstream of the tufA gene. The fus gene is located within the str operon and is followed by one tRNA gene as well as by the genes secE and nusG, which are located in the 3' region of tufB in E. coli. This atypical disposition of genes suggests that intrachromosomal recombination between duplicated tuf genes has contributed to the evolution of the unique genomic architecture of R. prowazekii.
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Unusual organization of the rRNA genes in Rickettsia prowazekii.
Journal of bacteriology, 1995Co-Authors: Siv G. E. Andersson, H H Winkler, Alireza Zomorodipour, Charles G. KurlandAbstract:We describe here the organization of the rRNA genes in Rickettsia prowazekii. In this organism, the 23S and the 5S rRNA genes are tightly linked to each other, whereas the 16S rRNA gene is separated from this cluster. The 23S-5S unit is preceded by the methionyl-tRNAfMet formyltransferase gene.
Siv G. E. Andersson - One of the best experts on this subject based on the ideXlab platform.
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Rickettsia prowazekii and Bartonella henselae: differences in the intracellular life styles revisited.
International journal of medical microbiology : IJMM, 2000Co-Authors: Siv G. E. Andersson, Christoph DehioAbstract:Within the alpha subdivision of proteobacteria, the arthropod-borne human pathogens Rickettsia prowazekii and Bartonella henselae provide examples of bacteria with obligate and facultative intracellular life styles, respectively. The complete genome sequence of R. prowazekii has been published, whereas the sequencing of the B. henselae genome is in its final stage. Here, we provide a brief overview of a comparative analysis of both genomes based on the delineated metabolic properties. The relative proportion of genes devoted to basic information processes is similar in the two genomes. In contrast, a full set of genes encoding proteins involved in the biosynthesis of amino acids and nucleotides is present in B. henselae, while the majority of these genes is absent from R. prowazekii. This suggests that B. henselae has a better potential for growth in the free-living mode, whereas R. prowazekii is more specialised to growth in an intracellular environment. Functional genomics will provide the potential to further resolve the genetic basis for successful human infections by these important parasites.
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The genome sequence of Rickettsia prowazekii and the origin of mitochondria
Nature, 1998Co-Authors: Siv G. E. Andersson, Herbert H. Winkler, Alireza Zomorodipour, Jan Andersson, Thomas Sicheritz-pontén, U. Cecilia M. Alsmark, Raf M. Podowski, A. Kristina Näslund, Ann-sofie Eriksson, Charles G. KurlandAbstract:We describe here the complete genome sequence (1,111,523 base pairs) of the obligate intracellular parasite Rickettsia prowazekii, the causative agent of epidemic typhus. This genome contains 834 p ...
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The genome sequence of Rickettsia prowazekii and the origin of mitochondria
Nature, 1998Co-Authors: Siv G. E. Andersson, Herbert H. Winkler, Alireza Zomorodipour, Thomas Sicheritz-pontén, U. Cecilia M. Alsmark, Raf M. Podowski, A. Kristina Näslund, Ann-sofie Eriksson, Jan O. Andersson, Charles G. KurlandAbstract:We describe here the complete genome sequence (1,111,523 base pairs) of the obligate intracellular parasite Rickettsia prowazekii , the causative agent of epidemic typhus. This genome contains 834 protein-coding genes. The functional profiles of these genes show similarities to those of mitochondrial genes: no genes required for anaerobic glycolysis are found in either R. prowazekii or mitochondrial genomes, but a complete set of genes encoding components of the tricarboxylic acid cycle and the respiratory-chain complex is found in R. prowazekii . In effect, ATP production in Rickettsia is the same as that in mitochondria. Many genes involved in the biosynthesis and regulation of biosynthesis of amino acids and nucleosides in free-living bacteria are absent from R. prowazekii and mitochondria. Such genes seem to have been replaced by homologues in the nuclear (host) genome. The R. prowazekii genome contains the highest proportion of non-coding DNA (24%) detected so far in a microbial genome. Such non-coding sequences may be degraded remnants of ‘neutralized’ genes that await elimination from the genome. Phylogenetic analyses indicate that R. prowazekii is more closely related to mitochondria than is any other microbe studied so far.
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Bioenergetics of the obligate intracellular parasite Rickettsia prowazekii.
Biochimica et biophysica acta, 1998Co-Authors: Siv G. E. AnderssonAbstract:Abstract Mitochondria are thought to be derived from an ancestor of the α-proteobacteria and more specifically from the Rickettsiaceae. The bioenergetic repertoire of the obligate intracellular parasite Rickettsia prowazekii is consistent with its postulated role as the ancestor of the mitochondria. For example, the R. prowazekii genome contains genes encoding components of the tricarboxylic acid cycle as well as of the electron transport system, but lacks genes to support glycolysis. In addition, the R. prowazekii genome contains multiple genes coding for adenine nucleotide translocators which enables this intracellular parasite to exploit the cytoplasmic ATP of its host cell as a source of energy. The aim of this review is to describe the different aspects of the bioenergetic system in R. prowazekii and to discuss the results of phylogenetic reconstructions based on a variety of bioenergetic molecules which shed light on the origin and evolution of the mitochondrial genomes.
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The Rickettsia prowazekii Genome: A Random Sequence Analysis
Microbial & comparative genomics, 1996Co-Authors: Siv G. E. Andersson, A. Kristina Näslund, Ann-sofie Eriksson, Morten S. Andersen, Charles G. KurlandAbstract:We describe here the first general survey of the genomic content and the coding capacity of the 1.1 Mb genome of Rickettsia prowazekii based on an analysis of a total of 200 kb of unique sequence data collected in a random manner. Based on nucleotide distribution profiles, we estimate that the R. prowazekii genome may have a coding density of 60%-70% and that it may contain a total of circa 800 genes. Here, we have tentatively identified and classified 173 of these genes. Our analysis suggests that the R. prowazekii genome is a highly derived, reduced genome that has lost many genes involved in amino acid biosynthetic pathways and regulatory functions. Furthermore, the R. prowazekii genome seems to lack glycolytic genes, but it does contain genes encoding components of the tricarboxylic acid cycle as well as of the electron transport system. We have also encountered a family of homologous genes coding for ATP/ADP translocases, as observed in several mitochondrial genomes. We relate these findings to previ...
