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At least 19 recordsLinked to original sources
PubMed2005

A bacterium belonging to the Rickettsiaceae family inhabits the cytoplasm of the marine ciliate Diophrys appendiculata (Ciliophora, Hypotrichia).

Bacteria of the family Rickettsiaceae (order Rickettsiales, alpha-Proteobacteria) are mainly known to be endosymbionts of arthropods with the capability to infect also vertebrate cells. Recently, they have also been found as leech endocytobionts. In the present paper, we report the first finding of a bacterium belonging to the family Rickettsiaceae in a natural population of a marine ciliate protozoan, namely Diophrys appendiculata, collected in the Baltic Sea. Bacteria were unambiguously identified through morphological characterization and the "full-cycle rRNA approach" (i.e., 16S rRNA gene characterization and use of specifically designed oligonucleotide probes for in situ detection). Symbionts are rod-shaped bacteria that grow freely in the cytoplasm of the host cell. They present two different morphotypes, similar in size, but different in cytoplasmic density. These are typical morphological features of members of the family Rickettsiaceae. 16S rRNA gene sequence showed that Diophrys symbionts share a high similarity value (>92%) with bacteria belonging to the genus Rickettsia. Phylogenetic analysis revealed that these new endosymbionts are clearly included in the clade of the family Rickettsiaceae, but they occupy an independent phylogenetic position with respect to members of the genus Rickettsia. This is the first report of a member of this family from a host protozoan and from a marine habitat. This result shows that this bacterial group is more diversified and widespread than supposed so far, and that its ecological relevance could until now have been underestimated. In light of these considerations, the two 16S rRNA oligonucleotide probes here presented, specific for members of the Rickettsiaceae, can represent useful tools for further researches on the presence and the spread of these microorganisms in the natural environment.

Animals↗
PubMed2001

Rickettsiaceae, rickettsia-like endosymbionts, and the origin of mitochondria.

Accumulating evolutionary data point to a monophyletic origin of mitochondria from the order Rickettsiales. This large group of obligate intracellular alpha-Proteobacteria includes the family Rickettsiaceae and several rickettsia-like endosymbionts (RLEs). Detailed phylogenetic analysis of small subunit (SSU) rRNA and chaperonin 60 (Cpn60) sequences testify to polyphyly of the Rickettsiales, and consistently indicate a sisterhood of Rickettsiaceae and mitochondria that excludes RLEs. Thus RLEs are considered as the nearest extant relatives of an extinct last common ancestor of mitochondria and rickettsiae. Phylogenetic inferences prompt the following assumptions. (1) Mitochondrial origin has been predisposed by the long-term endosymbiotic relationship between rickettsia-like bacteria and proto-eukaryotes, in which many endosymbiont genes have been lost while some indispensable genes have been transferred to the host genome. (2) The obligate dependence of rickettsiae upon a eukaryotic host rests on the import of proteins encoded by these transferred genes. The nature of a proto-eukaryotic cell still remains elusive. The divergence of Rickettsiaceae and mitochondria based on Cpn60, and the evolutionary history of two aminoacyl-tRNA synthetases favor the hypothesis that it was a chimera created by fusion of an archaebacterium and a eubacterium not long before an endosymbiotic event. These and other, mostly biochemical data suggest that all the mitochondrion-related organelles, i.e., both aerobically and anaerobically respiring mitochondria and hydrogenosomes, have originated from the same RLE, while hydrogenosomal energy metabolism may have a separate origin resulting from a eubacterial fusion partner.

Animals↗
PubMed1998

A phylogenetic analysis of the cytochrome b and cytochrome c oxidase I genes supports an origin of mitochondria from within the Rickettsiaceae.

We have cloned and sequenced the genes encoding cytochrome b (cob) and cytochrome c oxidase subunit I (cox1) from Rickettsia prowazekii, a member of the alpha-proteobacteria. The phylogenetic analysis supports the hypothesis that mitochondria are derived from the alpha-proteobacteria and more specifically from within the Rickettsiaceae. We have estimated that the common ancestor of mitochondria and Rickettsiaceae dates back to more than 1500 million years ago.

Amino Acids↗
PubMed1990

Transformation of Rochalimaea quintana, a member of the family Rickettsiaceae.

Rochalimaea quintana is the only member of the family Rickettsiaceae that can be grown in vitro. Because of its relationship to the other members of this family, techniques developed to transform R. quintana might be applicable to the obligate intracellular bacteria of the Rickettsiaceae. These procedures are critical to understanding mechanisms of pathogenesis and the nature of obligate intracellular growth. A transformation procedure for R. quintana has been established by using electroporation techniques. Several cosmids or plasmids with replicons RK2 and RSF1010 have been successfully used to transform this organism. Transformants were obtained by selection for antibiotic resistance to chloramphenicol or kanamycin. Plasmid retention and replication has been verified by Southern blot analysis and chloramphenicol acetyltransferase assay. Experimentation with different voltage field strengths and pulse times indicate that 12.5 kV/cm at 10 ms (25 microF and 400 omega) was optimal, giving a transformation frequency of approximately 0.3% and 3 x 10(5) transformants per microgram of DNA.

Blotting, Southern↗
PubMed2002

Host-symbiont conflicts: positive selection on an outer membrane protein of parasitic but not mutualistic Rickettsiaceae.

The Rickettsiaceae is a family of intracellular bacterial symbionts that includes both vertically transmitted parasites that spread by manipulating the reproduction of their host (Wolbachia in arthropods) and horizontally transmitted parasites (represented by Cowdria ruminantium), and mutualists (Wolbachia pipientis in nematode worms). We have investigated the nature of natural selection acting on an outer membrane protein, the wsp gene in Wolbachia and its homologue map1 in Cowdria, thought likely to be involved in host-parasite interactions in these bacteria. The ratio of nonsynonymous to synonymous substitution rates (d(N)/d(S)) at individual amino acid sites or at lineages within the gene's phylogeny was estimated using maximum likelihood models of codon substitution. The first hypothesis we tested was that this protein is under positive selection in the parasitic but not in the mutualistic Rickettsiaceae. This hypothesis was supported as positive selection and was detected in Cowdria and arthropod Wolbachia sequence evolution but not in the evolution of Wolbachia sequences from nematodes. Furthermore, this selection was concentrated outside the transmembrane region of the protein and, therefore, in the regions of the protein that may interact with the host. The second hypothesis tested was that positive selection would be stronger in the strains of arthropod Wolbachia that distort the host sex ratio than in those that induce cytoplasmic incompatibility. However, we found no support for this hypothesis. In conclusion, our results are consistent with the hypothesis that antagonistic coevolution causes faster evolution of surface protein sequences in parasites than in mutualists. Confirmation of this conclusion awaits the replication of these results both in additional genes and across more bacterial taxa. The regions of the wsp and map1 genes we identified as likely to be involved in host-parasite arms races should be examined in future studies of parasite virulence and host immune responses, and during the design of vaccines.

Amino Acid Sequence↗
PubMed1995

Antibodies against Rickettsiaceae in dogs of Setúbal, Portugal.

An indirect fluorescent antibody test was performed on sera collected from dogs housed in the municipal kennel of Setúbal to assess the prevalence of antibodies to Ehrlichia canis, the causative agent of canine ehrlichiosis and to Rickettsia conorii, agent of boutonneuse fever in humans. Two other members of the family Rickettsiaceae, Coxiella burnetii and Rickettsia typhi, were included in the serosurvey. Of the 104 dogs tested, 85.6% had antibodies to R. conorii, 50% to E. canis, 26.9% to R. typhi, and 4.8% to C. burnetii. These high seroprevalence rates of dogs with antibodies all year around against Rickettsiaceae suggest that physicians, public health officers and veterinarians should more frequently consider the diagnosis of these infections in Portugal.

Animals↗
PubMed2001

Reorganization of genera in the families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales: unification of some species of Ehrlichia with Anaplasma, Cowdria with Ehrlichia and Ehrlichia with Neorickettsia, descriptions of six new species combinations and designation of Ehrlichia equi and 'HGE agent' as subjective synonyms of Ehrlichia phagocytophila.

The genera Anaplasma, Ehrlichia, Cowdria, Neorickettsia and Wolbachia encompass a group of obligate intracellular bacteria that reside in vacuoles of eukaryotic cells and were previously placed in taxa based upon morphological, ecological, epidemiological and clinical characteristics. Recent genetic analyses of 16S rRNA genes, groESL and surface protein genes have indicated that the existing taxa designations are flawed. All 16S rRNA gene and groESL sequences deposited in GenBank prior to 2000 and selected sequences deposited thereafter were aligned and phylogenetic trees and bootstrap values were calculated using the neighbour-joining method and compared with trees generated with maximum-probability, maximum-likelihood, majority-rule consensus and parsimony methods. Supported by bootstrap probabilities of at least 54%, 16S rRNA gene comparisons consistently clustered to yield four distinct clades characterized roughly as Anaplasma (including the Ehrlichia phagocytophila group, Ehrlichia platys and Ehrlichia bovis) with a minimum of 96.1% similarity, Ehrlichia (including Cowdria ruminantium) with a minimum of 97.7% similarity, Wolbachia with a minimum of 95.6% similarity and Neorickettsia (including Ehrlichia sennetsu and Ehrlichia risticii) with a minimum of 94.9% similarity. Maximum similarity between clades ranged from 87.1 to 94.9%. Insufficient differences existed among E. phagocytophila, Ehrlichia equi and the human granulocytic ehrlichiosis (HGE) agent to support separate species designations, and this group was at least 98.2% similar to any Anaplasma species. These 16S rRNA gene analyses are strongly supported by similar groESL clades, as well as biological and antigenic characteristics. It is proposed that all members of the tribes Ehrlichieae and Wolbachieae be transferred to the family Anaplasmataceae and that the tribe structure of the family Rickettsiaceae be eliminated. The genus Anaplasma should be emended to include Anaplasma (Ehrlichia) phagocytophila comb. nov. (which also encompasses the former E. equi and the HGE agent), Anaplasma (Ehrlichia) bovis comb. nov. and Anaplasma (Ehrlichia) platys comb. nov., the genus Ehrlichia should be emended to include Ehrlichia (Cowdria) ruminantium comb. nov. and the genus Neorickettsia should be emended to include Neorickettsia (Ehrlichia) risticii comb. nov. and Neorickettsia (Ehrlichia) sennetsu comb. nov.

Anaplasma↗
PubMedDate not supplied

[Lipopolysaccharides of Rickettsiaceae and the Limulus endotoxin assay].

The A.A. have examined by Limulus endotoxin assay some LPS preparations from R. typhi, R. slovaka, C. burnetti phase I and II, as a demonstration of endotoxicity. All the preparations tested were able to gel the Limulus amoebocyte lysates, even if to a different degree of reactivity. The results add credibility to the hypothesis that LPS from Rickettsiaceae can represent at least in part the pathogenetic mediators of some manifestations described in Rickettsiosis; however, without endotoxin assay in the blood of patients, one cannot assume to this be true.

Coxiella↗
PubMed1984

Rickettsiaceae and Chlamydiaceae: comparative electron microscopic studies.

The structure and cytopathology of obligate intracellular bacteria belonging to families Rickettsiaceae and Chlamydiaceae and their interaction with eukaryotic host cells were compared in electron microscopic studies. "Rickettsia-like" and "chlamydia-like" types of organization of bacterial cells and their interaction with host cells are presented. The rickettsia-like type is characterized by short rod-shaped cells multiplying freely ( extravacuolarly ) in the cytoplasm or nucleoplasm of the host cell; the chlamydia-like type has spherical cells multiplying inside the cytoplasmic vacuole limited by the host membrane. The rickettsia-like type includes the genus Rickettsia and rod-shaped symbionts from genera Wolbachia and Symbiotes ; the chlamydia-like type falls into genera Chlamydia, Ehrlichia, Cowdria and Neorickettsia . The transitional types represented by Wolbachia persica (type 1), Coxiella and Rickettsiella (type 2) are also described. The possible evolutional relationships of the genera comprising both families are considered and their classification is proposed.

Chlamydia↗
PubMed1995

Detection of mip-like sequences and Mip-related proteins within the family Rickettsiaceae.

The Mip surface protein, a prokaryotic analog of the FK506-binding proteins, enhances the ability of Legionella pneumophila to infect macrophages and protozoa. Using mip-specific probes and low-stringency Southern hybridizations, we have detected DNA sequences homologous to mip within Coxiella burnetii and Rochalimaea quintana. Using specific anti-Mip antisera and immunoblot analysis, we also detected Mip-related proteins within these bacteria as well as within Rickettsia and Ehrlichia species. These data suggest that Mip-related proteins have broad significance for host-parasite interactions. However, they also indicate that care must be exercised when using mip probes or anti-Mip antibodies for the detection of Legionella organisms in water or clinical samples.

Bacterial Proteins↗
PubMed1990

Attempted transmission of Ehrlichia risticii (Rickettsiaceae) with Stomoxys calcitrans (Diptera: Muscidae).

Experimental transmission of Ehrlichia risticii, the causal agent of Potomac horse fever, was attempted with adult stable flies, Stomoxys calcitrans, (L.) using two feeding schedules. In schedule A, a set of 140 flies was allowed to feed once on an experimentally infected donor pony and once 24 h later on a recipient pony. A different set of flies was used each day for a 12-d period. In schedule B, 240 flies were allowed to feed once daily for 12 consecutive d on the donor pony followed by five consecutive daily feedings on the recipient pony. E. risticii was isolated from the blood of the experimentally infected pony during the entire fly-feeding schedule. The recipient pony did not develop clinical signs of Potomac horse fever and remained seronegative to E. risticii up to 60 d after the last stable fly feeding. Mice injected intraperitoneally with emulsions of schedule A and B stable flies were seronegative for E. risticii 30 d after inoculation, and ehrlichial organisms were not demonstrated in impression smears from the digestive tracts of the flies. The stable fly did not transmit E. risticii under these experimental conditions.

Animals↗
PubMed1990

Genetic relationships among the members of the family rickettsiaceae as shown by DNA restriction fragment polymorphism analysis.

The genetic diversity of members of the genus Rickettsia was examined using restriction site polymorphisms found within a series of DNA fragments scattered throughout the genome. Rickettsia belli, R. akari, and R. australis were the most divergent species when compared to the other species examined. These three species were also not closely related to each other. The other examined species were more tightly clustered. This survey also examined the genetic diversity within several species. The unexpected finding of this survey is that several species of rickettsia are as closely related to the surveyed strains of R. rickettsii as these strains are to each other. These results indicate that R. sibirica, R. parkeri, R. rickettsii, and an unnamed isolate from Africa are likely to be strains of a single rickettsial species of worldwide distribution. R. conorii was very closely related to this R. rickettsii-containing group but is likely to remain in a genetically distinct category as the data base expands.

DNA, Bacterial↗
PubMed2005

Factors influencing in vitro infectivity and growth of Rickettsia peacockii (Rickettsiales: Rickettsiaceae), an endosymbiont of the Rocky Mountain wood tick, Dermacentor andersoni (Acari, Ixodidae).

Rickettsia peacockii, a spotted fever group rickettsia, is a transovarially transmitted endosymbiont of Rocky Mountain wood ticks, Dermacentor andersoni. This rickettsia, formerly known as the East Side Agent and restricted to female ticks, was detected in a chronically infected embryonic cell line, DAE100, from D. andersoni. We examined infectivity, ability to induce cytopathic effect (CPE) and host cell specificity of R. peacockii using cultured arthropod and mammalian cells. Aposymbiotic DAE100 cells were obtained using oxytetracycline or incubation at 37 degrees C. Uninfected DAE100 sublines grew faster than the parent line, indicating R. peacockii regulation of host cell growth. Nevertheless, DAE100 cellular defenses exerted partial control over R. peacockii growth. Rickettsiae existed free in the cytosol of DAE100 cells or within autophagolysosomes. Exocytosed rickettsiae accumulated in the medium and were occasionally contained within host membranes. R. peacockii multiplied in other cell lines from the hard ticks D. andersoni, Dermacentor albipictus, Ixodes scapularis, and Ixodes ricinus; the soft tick Carios capensis; and the lepidopteran Trichoplusia ni. Lines from the tick Amblyomma americanum, the mosquito Aedes albopictus, and two mammalian cell lines were non-permissive to R. peacockii. High cell densities facilitated rickettsial spread within permissive cell cultures, and an inoculum of one infected to nine uninfected cells resulted in the greatest yield of infected tick cells. Cell-free R. peacockii also were infectious for tick cells and centrifugation onto cell layers enhanced infectivity approximately 100-fold. The ability of R. peacockii to cause mild CPE suggests that its pathogenicity is not completely muted. An analysis of R. peacockii-cell interactions in comparison to pathogenic rickettsiae will provide insights into host cell colonization mechanisms.

Animals↗
PubMed2001

Molecular phylogeny and biogeography of North American isolates of Anaplasma marginale (Rickettsiaceae: Ehrlichieae).

Anaplasma marginale (A. marginale) is a tick-borne ehrlichial pathogen of cattle that causes the disease anaplasmosis. Six major surface proteins (MSPs) have been identified on A. marginale from cattle and ticks of which three, MSP1a, MSP4 and MSP5, are from single genes and do not vary within isolates. The other three, MSP1b, MSP2 and MSP3, are from multigene families and may vary antigenically in persistently infected cattle. Several geographic isolates have been identified in the United States which differ in morphology, protein sequence and antigenic properties. An identifying characteristic of A. marginale isolates is the molecular weight of MSP1a which varies in size among isolates due to different numbers of tandemly repeated 28-29 amino acid peptides. For these studies, genes coding for A. marginale MSP1a and MSP4, msp1alpha and msp4, respectively, from nine North American isolates were sequenced for phylogenetic analysis. The phylogenetic analysis strongly supports the existence of a south-eastern clade of A. marginale comprised of Virginia and Florida isolates. Analysis of 16S rDNA fragment sequences from the A. marginale tick vector, Dermacentor variabilis, from various areas of the United States was used to evaluate possible vector-parasite co-evolution. Our phylogenetic analysis supports identity between the most parsimonious tree from the A. marginale MSP gene data and the tree that reflected the western and eastern clades of D. variabilis. These phylogenetic analyses provide information that may be important to consider when developing control strategies for anaplasmosis in the United States.

Amino Acid Sequence↗
PubMed1994

Failed vertical transmission of Rickettsia tsutsugamushi (Rickettsiales: Rickettsiaceae) acquired from rickettsemic mice by Leptotrombidium pallidum (Acari: trombiculidae).

Larvae of Leptotrombidium pallidum (Nagayo, Miyagawa, Mitamura & Tamiya) from uninfected laboratory colonies were fed on mice infected with Rickettsia tsutsugamushi (Hayashi) Ogata. Infection of the chiggers with R. tsutsugamushi was determined by passage of chigger exudates into ddY mice. The passage method was modified so that an inoculum was considered to be positive when R. tsutsugamushi or anti-R. tsutsugamushi antibody, or both, were detected in mice up to the third blind passage. R. tsutsugamushi was detected in six of 18 larvae (33.3%) and in all developmental stages. In adults, five of 18 males and 10 of 46 females were infected with R. tsutsugamushi. In L. fuji (Kuwata, Berge & Philip), R. tsutsugamushi was not found in 57 engorged larvae fed on rickettsemic mice but was found in a very low percentage of deutonymphs and adults. Female L. pallidum from larvae fed on infected mice were paired individually, and F1 larvae were collected. Although eight females were found to be positive for R. tsutsugamushi, the rickettsia was not detected in 12 pools (249 larvae) of F1 larvae from these infected females. We concluded that uninfected mites became infected by feeding on rickettsemic mice at comparatively high rates depending on the species and transmitted this infection transstadially to succeeding life stages, but not vertically to larvae in the following F1 generation.

Animals↗