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Giulio Petroni - One of the best experts on this subject based on the ideXlab platform.
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‘Candidatus Megaira polyxenophila ’ gen. nov., sp. nov.: Considerations on Evolutionary History, Host Range and Shift of Early Divergent Rickettsiae
2016Co-Authors: Martina Schrallhammer, Claudia Vannini, Franco Verni, Michael Schweikert, Stefano Galati, Giulio PetroniAbstract:‘‘Neglected Rickettsiaceae’ ’ (i.e. those harboured by non-hematophagous eukaryotic hosts) display greater phylogenetic variability and more widespread dispersal than pathogenic ones; yet, the knowledge about their actual host range and host shift mechanism is scarce. The present work reports the characterization following the full-cycle rRNA approach (SSU rRNA sequence, specific in situ hybridization, and ultrastructure) of a novel rickettsial bacterium, herewith proposed as ’Candidatus Megaira polyxenophila ’ gen. nov., sp. nov. We found it in association with four different free-living ciliates (Diophrys oligothrix, Euplotes octocarinatus, Paramecium caudatum, and Spirostomum sp., all belonging to Alveolata, Ciliophora); furthermore it was recently observed as intracellular occurring in Carteria cerasiformis and Pleodorina japonica (Chlorophyceae, Chlorophyta). Phylogenetic analyses demonstrated the belonging of the candidate new genus to the family Rickettsiaceae (Alphaproteobacteria, Rickettsiales) as a sister group of the genus Rickettsia. In situ observations revealed the ability of the candidate new species to colonize either nuclear or cytoplasmic compartments, depending on the host organism. The presence of the same bacterial species within different, evolutionary distant, hosts indicates that ’Candidatus Megaira polyxenophila ’ recently underwent several distinct host shifts, thus suggesting the existence of horizontal transmission pathways. We consider these findings as indicative of an unexpected spread of rickettsial infections in aquatic communities, possibly by means of trophic interactions, and hence propose a new interpretation of the origin an
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Flagellar Movement in Two Bacteria of the Family Rickettsiaceae: A Re-Evaluation of Motility in an Evolutionary Perspective
2016Co-Authors: Claudia Vannini, Sergei I Fokin, Vittorio Boscaro, Konstantin A. Benken, Timofei I. Mironov, Michael Schweikert, Elena V. Sabaneyeva, Giulio PetroniAbstract:Bacteria of the family Rickettsiaceae have always been largely studied not only for their importance in the medical field, but also as model systems in evolutionary biology. In fact, they share a recent common ancestor with mitochondria. The most studied species, belonging to genera Rickettsia and Orientia, are hosted by terrestrial arthropods and include many human pathogens. Nevertheless, recent findings show that a large part of Rickettsiaceae biodiversity actually resides outside the group of well-known pathogenic bacteria. Collecting data on these recently described non-conventional members of the family is crucial in order to gain information on ancestral features of the whole group. Although bacteria of the family Rickettsiaceae, and of the whole order Rickettsiales, are formally described as non-flagellated prokaryotes, some recent findings renewed the debate about this feature. In this paper we report the first finding of members of the family displaying numerous flagella and active movement inside their host cells. These two new taxa are hosted in aquatic environments by protist ciliates and are described here by means of ultrastructural and molecular characterization. Data here reported suggest that the ancestor of Rickettsiales displayed flagellar movement and re-evaluate the hypothesis that motility played a key-role in the origin of mitochondria. Moreover, our study highlights that the aquatic environment represents a well exploited habitat for bacteria of the family Rickettsiaceae. Our results encourage a deep re-consideration of ecological an
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Flagellar Movement in Two Bacteria of the Family Rickettsiaceae: A Re-Evaluation of Motility in an Evolutionary Perspective
2014Co-Authors: Claudia Vannini, Sergei I Fokin, Filippo Ferrantini, Vittorio Boscaro, Konstantin A. Benken, Timofei I. Mironov, Michael Schweikert, Elena V. Sabaneyeva, Hans-dieter Görtz, Giulio PetroniAbstract:Bacteria of the family Rickettsiaceae have always been largely studied not only for their importance in the medical field, but also as model systems in evolutionary biology. In fact, they share a recent common ancestor with mitochondria. The most studied species, belonging to genera Rickettsia and Orientia, are hosted by terrestrial arthropods and include many human pathogens. Nevertheless, recent findings show that a large part of Rickettsiaceae biodiversity actually resides outside the group of well-known pathogenic bacteria. Collecting data on these recently described non-conventional members of the family is crucial in order to gain information on ancestral features of the whole group. Although bacteria of the family Rickettsiaceae, and of the whole order Rickettsiales, are formally described as non-flagellated prokaryotes, some recent findings renewed the debate about this feature. In this paper we report the first finding of members of the family displaying numerous flagella and active movement inside their host cells. These two new taxa are hosted in aquatic environments by protist ciliates and are described here by means of ultrastructural and molecular characterization. Data here reported suggest that the ancestor of Rickettsiales displayed flagellar movement and re-evaluate the hypothesis that motility played a key-role in the origin of mitochondria. Moreover, our study highlights that the aquatic environment represents a well exploited habitat for bacteria of the family Rickettsiaceae. Our results encourage a deep re-consideration of ecological and morphological traits of the family and of the whole order.
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Fluorescence in situ hybridizations of Diophrys oligothrix DS212/4 and Paramecium caudatum SH42.
2013Co-Authors: Martina Schrallhammer, Claudia Vannini, Franco Verni, Filippo Ferrantini, Michael Schweikert, Hans-dieter Görtz, Stefano Galati, Giulio PetroniAbstract:Diophrys oligothrix DS212/4 was fixed with 4% formaldehyde in PBS (a-b-c) and Paramecium caudatum SH42 was fixed with 4% paraformaldehyde (d-e-f). (a, d) signal of Cy3-labeled probe MegPol436, specific for 'Candidatus Megaira polyxenophila'; (b) signal of Fluorescein-labeled probe Rick_527, targeting members of the Rickettsiaceae family; (c) merged image, (a) + (b); (e) signal of Fluorescein-labeled probe HoloCar698, specific for Holospora caryophila; (f) merged image, (d) + (e). Bar: 10 µm.
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Fluorescence in situ hybridizations of Spirostomum sp. 72 and Euplotes octocarinatus FL(12)-VI.
2013Co-Authors: Martina Schrallhammer, Claudia Vannini, Franco Verni, Filippo Ferrantini, Michael Schweikert, Hans-dieter Görtz, Stefano Galati, Giulio PetroniAbstract:Spirostomum sp. 72 was fixed with 4% osmium tetroxide (a-b-c) and Euplotes octocarinatus FL(12)-VI was fixed with 4% formaldehyde in PBS (d-e-f). (a) signal of Cy3-labeled probe MegPol436, specific for 'Candidatus Megaira polyxenophila' (macronuclei enhanced); (b) signal of Fluorescein-labeled probe EUB338 (macronuclei enhanced); (c) merged image, (a) + (b); (d) phase contrast; (e) signal of Fluorescein-labeled probe Rick_527, targeting members of the Rickettsiaceae family; (f) merged image, (d) + (e). Bar: 10 µm.
Franco Verni - One of the best experts on this subject based on the ideXlab platform.
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‘Candidatus Megaira polyxenophila ’ gen. nov., sp. nov.: Considerations on Evolutionary History, Host Range and Shift of Early Divergent Rickettsiae
2016Co-Authors: Martina Schrallhammer, Claudia Vannini, Franco Verni, Michael Schweikert, Stefano Galati, Giulio PetroniAbstract:‘‘Neglected Rickettsiaceae’ ’ (i.e. those harboured by non-hematophagous eukaryotic hosts) display greater phylogenetic variability and more widespread dispersal than pathogenic ones; yet, the knowledge about their actual host range and host shift mechanism is scarce. The present work reports the characterization following the full-cycle rRNA approach (SSU rRNA sequence, specific in situ hybridization, and ultrastructure) of a novel rickettsial bacterium, herewith proposed as ’Candidatus Megaira polyxenophila ’ gen. nov., sp. nov. We found it in association with four different free-living ciliates (Diophrys oligothrix, Euplotes octocarinatus, Paramecium caudatum, and Spirostomum sp., all belonging to Alveolata, Ciliophora); furthermore it was recently observed as intracellular occurring in Carteria cerasiformis and Pleodorina japonica (Chlorophyceae, Chlorophyta). Phylogenetic analyses demonstrated the belonging of the candidate new genus to the family Rickettsiaceae (Alphaproteobacteria, Rickettsiales) as a sister group of the genus Rickettsia. In situ observations revealed the ability of the candidate new species to colonize either nuclear or cytoplasmic compartments, depending on the host organism. The presence of the same bacterial species within different, evolutionary distant, hosts indicates that ’Candidatus Megaira polyxenophila ’ recently underwent several distinct host shifts, thus suggesting the existence of horizontal transmission pathways. We consider these findings as indicative of an unexpected spread of rickettsial infections in aquatic communities, possibly by means of trophic interactions, and hence propose a new interpretation of the origin an
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Fluorescence in situ hybridizations of Diophrys oligothrix DS212/4 and Paramecium caudatum SH42.
2013Co-Authors: Martina Schrallhammer, Claudia Vannini, Franco Verni, Filippo Ferrantini, Michael Schweikert, Hans-dieter Görtz, Stefano Galati, Giulio PetroniAbstract:Diophrys oligothrix DS212/4 was fixed with 4% formaldehyde in PBS (a-b-c) and Paramecium caudatum SH42 was fixed with 4% paraformaldehyde (d-e-f). (a, d) signal of Cy3-labeled probe MegPol436, specific for 'Candidatus Megaira polyxenophila'; (b) signal of Fluorescein-labeled probe Rick_527, targeting members of the Rickettsiaceae family; (c) merged image, (a) + (b); (e) signal of Fluorescein-labeled probe HoloCar698, specific for Holospora caryophila; (f) merged image, (d) + (e). Bar: 10 µm.
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Fluorescence in situ hybridizations of Spirostomum sp. 72 and Euplotes octocarinatus FL(12)-VI.
2013Co-Authors: Martina Schrallhammer, Claudia Vannini, Franco Verni, Filippo Ferrantini, Michael Schweikert, Hans-dieter Görtz, Stefano Galati, Giulio PetroniAbstract:Spirostomum sp. 72 was fixed with 4% osmium tetroxide (a-b-c) and Euplotes octocarinatus FL(12)-VI was fixed with 4% formaldehyde in PBS (d-e-f). (a) signal of Cy3-labeled probe MegPol436, specific for 'Candidatus Megaira polyxenophila' (macronuclei enhanced); (b) signal of Fluorescein-labeled probe EUB338 (macronuclei enhanced); (c) merged image, (a) + (b); (d) phase contrast; (e) signal of Fluorescein-labeled probe Rick_527, targeting members of the Rickettsiaceae family; (f) merged image, (d) + (e). Bar: 10 µm.
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candidatus anadelfobacter veles and candidatus cyrtobacter comes two new rickettsiales species hosted by the protist ciliate euplotes harpa ciliophora spirotrichea
Applied and Environmental Microbiology, 2010Co-Authors: Claudia Vannini, Karlheinz Schleifer, Franco Verni, Filippo Ferrantini, Wolfgang Ludwig, Giulio PetroniAbstract:The order Rickettsiales (Alphaproteobacteria) is a well-known group containing obligate endocellular prokaryotes. The order encompasses three families (Rickettsiaceae, Anaplasmataceae, and Holosporaceae) and a fourth, family-level cluster, which includes only one candidate species, “Candidatus Midichloria mitochondrii,” as well as several unnamed bacterial symbionts. The broad host range exhibited by the members of the “Candidatus Midichloria” clade suggests their eventual relevance for a better understanding of the evolution of symbiosis and host specificity of Rickettsiales. In this paper, two new bacteria belonging to the “Candidatus Midichloria” clade, hosted by two different strains of the ciliate protist Euplotes harpa, are described on the basis of ultrastructural observations, comparative 16S rRNA gene sequence analysis, and an estimation of the percentage of infection. Ultrastructure of these bacteria shows some unusual features: one has an electron-dense cytoplasm, and the other one lacks a symbiosomal membrane. The latter was up to now considered an exclusive feature of bacteria belonging to the family Rickettsiaceae. 16S rRNA gene phylogenetic analysis unambiguously places the new bacteria in the “Candidatus Midichloria” clade, although their phylogenetic relationships with other members of the clade are not clearly resolved. This is the first report of a ciliate-borne bacterium belonging to the “Candidatus Midichloria” clade. On the basis of the data obtained, the two bacteria are proposed as two new candidate genera and species, “Candidatus Anadelfobacter veles” and “Candidatus Cyrtobacter comes.”
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comes, ” Two New Rickettsiales Species Hosted by the Protist
2009Co-Authors: Ciliate Euplotes Harpa, Franco Verni, Giulio PetroniAbstract:The order Rickettsiales (Alphaproteobacteria) is a well-known group containing obligate endocellular pro-karyotes. The order encompasses three families (Rickettsiaceae, Anaplasmataceae, and Holosporaceae) and a fourth, family-level cluster, which includes only one candidate species, “Candidatus Midichloria mitochondrii,” as well as several unnamed bacterial symbionts. The broad host range exhibited by the members of the “Candidatus Midichloria ” clade suggests their eventual relevance for a better understanding of the evolution of symbiosis and host specificity of Rickettsiales. In this paper, two new bacteria belonging to the “Candidatus Midichloria ” clade, hosted by two different strains of the ciliate protist Euplotes harpa, are described on the basis of ultrastructural observations, comparative 16S rRNA gene sequence analysis, and an estimation of the percentage of infection. Ultrastructure of these bacteria shows some unusual features: one has an electron-dense cytoplasm, and the other one lacks a symbiosomal membrane. The latter was up to now considered an exclusive feature of bacteria belonging to the family Rickettsiaceae. 16S rRNA gene phylogenetic analysis unambiguously places the new bacteria in the “Candidatus Midichloria ” clade, although their phylogenetic relationships with other members of the clade are not clearly resolved. This is the first report of a ciliate-borne bacterium belonging to the “Candidatus Midichloria ” clade. On the basis of the data obtained, the two bacteria are proposed as two new candidate genera and species, “Candidatus Anadelfobacter veles ” and “Candidatu
Claudia Vannini - One of the best experts on this subject based on the ideXlab platform.
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‘Candidatus Megaira polyxenophila ’ gen. nov., sp. nov.: Considerations on Evolutionary History, Host Range and Shift of Early Divergent Rickettsiae
2016Co-Authors: Martina Schrallhammer, Claudia Vannini, Franco Verni, Michael Schweikert, Stefano Galati, Giulio PetroniAbstract:‘‘Neglected Rickettsiaceae’ ’ (i.e. those harboured by non-hematophagous eukaryotic hosts) display greater phylogenetic variability and more widespread dispersal than pathogenic ones; yet, the knowledge about their actual host range and host shift mechanism is scarce. The present work reports the characterization following the full-cycle rRNA approach (SSU rRNA sequence, specific in situ hybridization, and ultrastructure) of a novel rickettsial bacterium, herewith proposed as ’Candidatus Megaira polyxenophila ’ gen. nov., sp. nov. We found it in association with four different free-living ciliates (Diophrys oligothrix, Euplotes octocarinatus, Paramecium caudatum, and Spirostomum sp., all belonging to Alveolata, Ciliophora); furthermore it was recently observed as intracellular occurring in Carteria cerasiformis and Pleodorina japonica (Chlorophyceae, Chlorophyta). Phylogenetic analyses demonstrated the belonging of the candidate new genus to the family Rickettsiaceae (Alphaproteobacteria, Rickettsiales) as a sister group of the genus Rickettsia. In situ observations revealed the ability of the candidate new species to colonize either nuclear or cytoplasmic compartments, depending on the host organism. The presence of the same bacterial species within different, evolutionary distant, hosts indicates that ’Candidatus Megaira polyxenophila ’ recently underwent several distinct host shifts, thus suggesting the existence of horizontal transmission pathways. We consider these findings as indicative of an unexpected spread of rickettsial infections in aquatic communities, possibly by means of trophic interactions, and hence propose a new interpretation of the origin an
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Flagellar Movement in Two Bacteria of the Family Rickettsiaceae: A Re-Evaluation of Motility in an Evolutionary Perspective
2016Co-Authors: Claudia Vannini, Sergei I Fokin, Vittorio Boscaro, Konstantin A. Benken, Timofei I. Mironov, Michael Schweikert, Elena V. Sabaneyeva, Giulio PetroniAbstract:Bacteria of the family Rickettsiaceae have always been largely studied not only for their importance in the medical field, but also as model systems in evolutionary biology. In fact, they share a recent common ancestor with mitochondria. The most studied species, belonging to genera Rickettsia and Orientia, are hosted by terrestrial arthropods and include many human pathogens. Nevertheless, recent findings show that a large part of Rickettsiaceae biodiversity actually resides outside the group of well-known pathogenic bacteria. Collecting data on these recently described non-conventional members of the family is crucial in order to gain information on ancestral features of the whole group. Although bacteria of the family Rickettsiaceae, and of the whole order Rickettsiales, are formally described as non-flagellated prokaryotes, some recent findings renewed the debate about this feature. In this paper we report the first finding of members of the family displaying numerous flagella and active movement inside their host cells. These two new taxa are hosted in aquatic environments by protist ciliates and are described here by means of ultrastructural and molecular characterization. Data here reported suggest that the ancestor of Rickettsiales displayed flagellar movement and re-evaluate the hypothesis that motility played a key-role in the origin of mitochondria. Moreover, our study highlights that the aquatic environment represents a well exploited habitat for bacteria of the family Rickettsiaceae. Our results encourage a deep re-consideration of ecological an
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Flagellar Movement in Two Bacteria of the Family Rickettsiaceae: A Re-Evaluation of Motility in an Evolutionary Perspective
2014Co-Authors: Claudia Vannini, Sergei I Fokin, Filippo Ferrantini, Vittorio Boscaro, Konstantin A. Benken, Timofei I. Mironov, Michael Schweikert, Elena V. Sabaneyeva, Hans-dieter Görtz, Giulio PetroniAbstract:Bacteria of the family Rickettsiaceae have always been largely studied not only for their importance in the medical field, but also as model systems in evolutionary biology. In fact, they share a recent common ancestor with mitochondria. The most studied species, belonging to genera Rickettsia and Orientia, are hosted by terrestrial arthropods and include many human pathogens. Nevertheless, recent findings show that a large part of Rickettsiaceae biodiversity actually resides outside the group of well-known pathogenic bacteria. Collecting data on these recently described non-conventional members of the family is crucial in order to gain information on ancestral features of the whole group. Although bacteria of the family Rickettsiaceae, and of the whole order Rickettsiales, are formally described as non-flagellated prokaryotes, some recent findings renewed the debate about this feature. In this paper we report the first finding of members of the family displaying numerous flagella and active movement inside their host cells. These two new taxa are hosted in aquatic environments by protist ciliates and are described here by means of ultrastructural and molecular characterization. Data here reported suggest that the ancestor of Rickettsiales displayed flagellar movement and re-evaluate the hypothesis that motility played a key-role in the origin of mitochondria. Moreover, our study highlights that the aquatic environment represents a well exploited habitat for bacteria of the family Rickettsiaceae. Our results encourage a deep re-consideration of ecological and morphological traits of the family and of the whole order.
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Fluorescence in situ hybridizations of Diophrys oligothrix DS212/4 and Paramecium caudatum SH42.
2013Co-Authors: Martina Schrallhammer, Claudia Vannini, Franco Verni, Filippo Ferrantini, Michael Schweikert, Hans-dieter Görtz, Stefano Galati, Giulio PetroniAbstract:Diophrys oligothrix DS212/4 was fixed with 4% formaldehyde in PBS (a-b-c) and Paramecium caudatum SH42 was fixed with 4% paraformaldehyde (d-e-f). (a, d) signal of Cy3-labeled probe MegPol436, specific for 'Candidatus Megaira polyxenophila'; (b) signal of Fluorescein-labeled probe Rick_527, targeting members of the Rickettsiaceae family; (c) merged image, (a) + (b); (e) signal of Fluorescein-labeled probe HoloCar698, specific for Holospora caryophila; (f) merged image, (d) + (e). Bar: 10 µm.
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Fluorescence in situ hybridizations of Spirostomum sp. 72 and Euplotes octocarinatus FL(12)-VI.
2013Co-Authors: Martina Schrallhammer, Claudia Vannini, Franco Verni, Filippo Ferrantini, Michael Schweikert, Hans-dieter Görtz, Stefano Galati, Giulio PetroniAbstract:Spirostomum sp. 72 was fixed with 4% osmium tetroxide (a-b-c) and Euplotes octocarinatus FL(12)-VI was fixed with 4% formaldehyde in PBS (d-e-f). (a) signal of Cy3-labeled probe MegPol436, specific for 'Candidatus Megaira polyxenophila' (macronuclei enhanced); (b) signal of Fluorescein-labeled probe EUB338 (macronuclei enhanced); (c) merged image, (a) + (b); (d) phase contrast; (e) signal of Fluorescein-labeled probe Rick_527, targeting members of the Rickettsiaceae family; (f) merged image, (d) + (e). Bar: 10 µm.
Keisuke Nakayama - One of the best experts on this subject based on the ideXlab platform.
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genome comparison and phylogenetic analysis of orientia tsutsugamushi strains
DNA Research, 2010Co-Authors: Keisuke Nakayama, Hiroshi Urakami, Ken Kurokawa, Masahiro Fukuhara, Seigo Yamamoto, Kazuko Yamazaki, Yoshitoshi Ogura, Tadasuke Ooka, Tetsuya HayashiAbstract:Orientia tsutsugamushi (OT) is an obligate intracellular bacterium belonging to the family Rickettsiaceae and is the causative agent of scrub typhus, or Tsutsugamushi disease. The complete genome sequences of two OT strains (Boryong and Ikeda) have recently been determined. In the present study, we performed a fine genome sequence comparison of these strains. Our results indicate that although the core gene set of the family Rickettsiaceae is highly conserved between the two strains, a common set of repetitive sequences have been explosively amplified in both genomes. These amplified repetitive sequences have induced extensive genome shuffling and duplications and deletions of many genes. On the basis of the results of the genome sequence comparison, we selected 11 housekeeping genes and carried out multilocus sequence analysis of OT strains using the nucleotide sequences of these genes. This analysis revealed for the first time the phylogenetic relationships of representative OT strains. Furthermore, the results suggest the presence of an OT lineage with higher potential for virulence, which may explain the clinical and epidemiological differences between ‘classic’ and ‘new’ types of Tsutsugamushi disease in Japan.
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the whole genome sequencing of the obligate intracellular bacterium orientia tsutsugamushi revealed massive gene amplification during reductive genome evolution
DNA Research, 2008Co-Authors: Keisuke Nakayama, Hiroshi Urakami, Ken Kurokawa, Masahiro Fukuhara, Atsushi Yamashita, Takuya Morimoto, Michihiro Ogawa, Makoto Ohnishi, Ikuo Uchiyama, Yoshitoshi OguraAbstract:Scrub typhus (‘Tsutsugamushi’ disease in Japanese) is a mite-borne infectious disease. The causative agent is Orientia tsutsugamushi, an obligate intracellular bacterium belonging to the family Rickettsiaceae of the subdivision alpha-Proteobacteria. In this study, we determined the complete genome sequence of O. tsutsugamushi strain Ikeda, which comprises a single chromosome of 2 008 987 bp and contains 1967 protein coding sequences (CDSs). The chromosome is much larger than those of other members of Rickettsiaceae, and 46.7% of the sequence was occupied by repetitive sequences derived from an integrative and conjugative element, 10 types of transposable elements, and seven types of short repeats of unknown origins. The massive amplification and degradation of these elements have generated a huge number of repeated genes (1196 CDSs, categorized into 85 families), many of which are pseudogenes (766 CDSs), and also induced intensive genome shuffling. By comparing the gene content with those of other family members of Rickettsiacea, we identified the core gene set of the family Rickettsiaceae and found that, while much more extensive gene loss has taken place among the housekeeping genes of Orientia than those of Rickettsia, O. tsutsugamushi has acquired a large number of foreign genes. The O. tsutsugamushi genome sequence is thus a prominent example of the high plasticity of bacterial genomes, and provides the genetic basis for a better understanding of the biology of O. tsutsugamushi and the pathogenesis of ‘Tsutsugamushi’ disease.
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doi:10.1093/dnares/dsn011 The Whole-genome Sequencing of the Obligate Intracellular Bacterium Orientia tsutsugamushi Revealed Massive Gene Amplification During
2008Co-Authors: Reductive Genome Evolution, Hiroshi Urakami, Keisuke Nakayama, Ken Kurokawa, Masahiro Fukuhara, Atsushi Yamashita, Takuya Morimoto, Michihiro Ogawa, Makoto Ohnishi, Ikuo UchiyamaAbstract:Scrub typhus (‘Tsutsugamushi ’ disease in Japanese) is a mite-borne infectious disease. The causative agent is Orientia tsutsugamushi, an obligate intracellular bacterium belonging to the family Rickettsiaceae of the subdivision alpha-Proteobacteria. In this study, we determined the complete genome sequence of O. tsutsugamushi strain Ikeda, which comprises a single chromosome of 2 008 987 bp and contains 1967 protei
Hisayoshi Nozaki - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Two Different Rickettsial Bacteria Invading
2016Co-Authors: Volvox Carteri, Kaoru Kawafune, Yuichi Hongoh, Takashi Hamaji, Tomoaki Sakamoto, Tetsuya Kurata, Shunsuke Hirooka, Shinya Miyagishima, Hisayoshi NozakiAbstract:Background Bacteria of the family Rickettsiaceae are principally associated with arthropods. Recently, endosymbionts of the Rickettsiaceae have been found in non-phagotrophic cells of the vol-vocalean green algae Carteria cerasiformis, Pleodorina japonica, and Volvox carteri. Such endosymbionts were present in only C. cerasiformis strain NIES-425 and V. carteri strain UTEX 2180, of various strains of Carteria and V. carteri examined, suggesting that rickettsial endosymbionts may have been transmitted to only a few algal strains very recently. Howev-er, in preliminary work, we detected a sequence similar to that of a rickettsial gene in the nu-clear genome of V. carteri strain EVE. Methodology/Principal Findings Here we explored the origin of the rickettsial gene-like sequences in the endosymbiont-lack-ing V. carteri strain EVE, by performing comparative analyses on 13 strains of V. carteri. By reference to our ongoing genomic sequence of rickettsial endosymbionts in C. cerasiformis strain NIES-425 cells, we confirmed that an approximately 9-kbp DNA sequence encom-passing a region similar to that of four rickettsial genes was present in the nuclear genome of V. carteri strain EVE. Phylogenetic analyses, and comparisons of the synteny of rickettsi-al gene-like sequences from various strains of V. carteri, indicated that the rickettsial gene-like sequences in the nuclear genome of V. carteri strain EVE were closely related to rickett-sial gene sequences of P. japonica, rather than those of V. carteri strain UTEX 2180
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two different rickettsial bacteria invading volvox carteri
PLOS ONE, 2015Co-Authors: Kaoru Kawafune, Yuichi Hongoh, Takashi Hamaji, Tomoaki Sakamoto, Tetsuya Kurata, Shunsuke Hirooka, Shinya Miyagishima, Hisayoshi NozakiAbstract:Background Bacteria of the family Rickettsiaceae are principally associated with arthropods. Recently, endosymbionts of the Rickettsiaceae have been found in non-phagotrophic cells of the volvocalean green algae Carteria cerasiformis, Pleodorina japonica, and Volvox carteri. Such endosymbionts were present in only C. cerasiformis strain NIES-425 and V. carteri strain UTEX 2180, of various strains of Carteria and V. carteri examined, suggesting that rickettsial endosymbionts may have been transmitted to only a few algal strains very recently. However, in preliminary work, we detected a sequence similar to that of a rickettsial gene in the nuclear genome of V. carteri strain EVE. Methodology/Principal Findings Here we explored the origin of the rickettsial gene-like sequences in the endosymbiont-lacking V. carteri strain EVE, by performing comparative analyses on 13 strains of V. carteri. By reference to our ongoing genomic sequence of rickettsial endosymbionts in C. cerasiformis strain NIES-425 cells, we confirmed that an approximately 9-kbp DNA sequence encompassing a region similar to that of four rickettsial genes was present in the nuclear genome of V. carteri strain EVE. Phylogenetic analyses, and comparisons of the synteny of rickettsial gene-like sequences from various strains of V. carteri, indicated that the rickettsial gene-like sequences in the nuclear genome of V. carteri strain EVE were closely related to rickettsial gene sequences of P. japonica, rather than those of V. carteri strain UTEX 2180. Conclusion/Significance At least two different rickettsial organisms may have invaded the V. carteri lineage, one of which may be the direct ancestor of the endosymbiont of V. carteri strain UTEX 2180, whereas the other may be closely related to the endosymbiont of P. japonica. Endosymbiotic gene transfer from the latter rickettsial organism may have occurred in an ancestor of V. carteri. Thus, the rickettsiae may be widely associated with V. carteri, and likely have often been lost during host evolution.
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Phylogenetic positions of rickettsial murB and ddlB gene-like sequences from endosymbiont-lacking strains of Volvox carteri.
2015Co-Authors: Kaoru Kawafune, Yuichi Hongoh, Takashi Hamaji, Tomoaki Sakamoto, Tetsuya Kurata, Shunsuke Hirooka, Shinya Miyagishima, Hisayoshi NozakiAbstract:The tree was inferred using the maximum-likelihood (ML) method based on 637 amino acid sites in translated and combined murB and ddlB gene/gene-like sequences from 30 operational taxonomic units of bacteria in the Rickettsiaceae, including possible endosymbionts (En) of algal hosts, and possible nuclear-encoded sequences from endosymbiont-lacking strains of V. carteri (bold). Bootstrap values (≥50%) for ML and maximum parsimony analyses are indicated at the respective nodes. The scale bar corresponds to 0.1 amino acid substitutions per position.
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a rickettsial endosymbiont inhabiting the cytoplasm of volvox carteri volvocales chlorophyceae
Phycologia, 2014Co-Authors: Kaoru Kawafune, Yuichi Hongoh, Hisayoshi NozakiAbstract:A bacterial endosymbiont was previously observed in the green alga Volvox carteri strain UTEX 2180 using transmission electron microscopy, although its phylogenetic status was unknown. Here, we identified the bacterial endosymbiont based on analyses of the 16S ribosomal RNA (rRNA) gene. The endosymbiont of V. carteri belongs to the “hydra group” characterized by non-arthropod hosts, within the eubacterial family Rickettsiaceae (Rickettsiales; Alphaproteobacteria). In the hydra group, the endosymbiont formed a clade with the endosymbionts of the volvocaleans Carteria cerasiformis and Pleodorina japonica and the ciliate Diophrys appendiculata but was separated from the endosymbionts of marine green macroalgae (Bryopsis spp.). Fluorescence in situ hybridization using a probe specific for the 16S rRNA of the V. carteri endosymbiont confirmed our molecular identification and the distribution of the endosymbiont within the host cytoplasm. Rickettsial endosymbionts were not detected in eight other strains of V. ...
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Ultrastructure of the rickettsial endosymbiont “MIDORIKO” in the green alga Carteria cerasiformis as revealed by high-pressure freezing and freeze-substitution fixation
Protoplasma, 2013Co-Authors: Kaoru Kawafune, Mayuko Sato, Kiminori Toyooka, Hisayoshi NozakiAbstract:Bacterial endosymbionts belonging to the family Rickettsiaceae were recently identified in the unicellular green alga Carteria cerasiformis , providing the first molecular evidence of rickettsial endosymbionts within photosynthetic eukaryotes. However, previous morphological studies using transmission electron microscopy (TEM) with conventional chemical fixation did not demonstrate whether the endosymbionts of C. cerasiformis have the diagnostic characteristics of the family Rickettsiaceae . In this study, we observed the rickettsial endosymbionts “ MIDORIKO ” within C. cerasiformis cells by TEM with high-pressure freezing and freeze-substitution fixation. The rickettsial endosymbionts resided directly in the C. cerasiformis cytoplasm without engulfing or encompassing membranes or vacuoles. The endosymbionts had a Gram-negative cell envelope composed of outer and inner bilayer membranes. The thicknesses of the outer and inner leaflets of the bacterial cell wall were almost identical. These morphological characteristics are consistent with those of the genus Rickettsia , but the cell wall structure differed from that of the genus Orientia within the family Rickettsiaceae .
