Genome sequences of the zoonotic pathogens Chlamydia psittaci 6BC and Cal10.
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ABSTRACT:
SUBMITTER: Grinblat-Huse V
PROVIDER: S-EPMC3147492 | biostudies-literature | 2011 Aug
REPOSITORIES: biostudies-literature
Publications
Genome sequences of the zoonotic pathogens Chlamydia psittaci 6BC and Cal10.
Grinblat-Huse Valerie V Drabek Elliott F EF Creasy Heather Huot HH Daugherty Sean C SC Jones Kristine M KM Santana-Cruz Ivette I Tallon Luke J LJ Read Timothy D TD Hatch Thomas P TP Bavoil Patrik P Myers Garry S A GS
Journal of bacteriology 20110527 15
Chlamydia psittaci is a highly prevalent avian pathogen and the cause of a potentially lethal zoonosis, causing life-threatening pneumonia in humans. We report the genome sequences of C. psittaci 6BC, the prototype strain of the species, and C. psittaci Cal10, a widely used laboratory strain. ...[more]
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Project description:Chlamydia psittaci is an avian pathogen and zoonotic agent of atypical pneumonia. The most pathogenic C. psittaci strains cluster into the 6BC clade, predicted to have recently emerged globally. Exposure to infected parrots is a risk factor with limited evidence also of an indirect exposure risk. Genome sequencing was performed on six Australian human and a single avian C. psittaci strain isolated over a 9 year period. Only one of the five human patients had explicit psittacine contact. Genomics analyses revealed that the Australian C. psittaci strains are remarkably similar, clustering tightly within the C. psittaci 6BC clade suggested to have been disseminated by South America parrot importation. Molecular clock analysis using the newly sequenced C. psittaci genomes predicted the emergence of the 6BC clade occurring approximately 2,000 years ago. These findings reveal the potential for an Australian natural reservoir of C. psittaci 6BC strains. These strains can also be isolated from seriously ill patients without explicit psittacine contact. The apparent recent and global spread of C. psittaci 6BC strains raises important questions over how this happened. Further studies may reveal whether the dissemination of this important zoonotic pathogen is linked to Australian parrot importation rather than parrots from elsewhere.
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Project description:Chlamydophila psittaci 6BC genome sequencing project
| PRJNA62889 | ENA
Project description:Chlamydophila psittaci 6BC genome sequencing
| PRJNA63149 | ENA
Project description:Chlamydiae are parasitic bacteria characterized by a temporally regulated developmental cycle. In the early stage of the cycle, metabolically inert elementary bodies reorganize to dividing reticulate bodies, a process about which little is known. The purpose of this investigation was to identify and clone chlamydial genes that are expressed preferentially during the early stage of the developmental cycle of Chlamydia psittaci 6BC. Several potential early genes were cloned with highly radioactive, host-free-generated RNA probes to screen a genomic library. One clone appeared to encode a gene that was particularly well expressed at 1 h postinfection. In further characterization, we found that it encodes two complete open reading frames and one partial open reading frame of 370 codons. The partial open reading frame, designated gltX, is very similar to bacterial glutamyl-tRNA synthetases and was demonstrated to be transcribed in vivo at 24 h postinfection by primer extension analysis. A lysine-rich open reading frame (LRO) of 117 codons was found upstream and divergent from gltX. The LRO lacks homology to known proteins, and we were unable to demonstrate that it is transcribed in vivo. The third open reading frame, of 182 codons, was found to be convergent with and partially overlap the LRO. It was confirmed to be preferentially expressed within the first 1.5 h of infection by Northern (RNA) blot analysis and was designated the early upstream open reading frame (EUO). Like the LRO, the EUO is not homologous to known proteins. A major potential transcription start site of the EUO was identified by primer extension analysis. However, the sequence upstream of the site does not closely resemble the consensus recognition sequences of bacterial sigma factors even though it is AT rich. The EUO is the first chlamydial gene specific to the early stage to be cloned and sequenced.
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Project description:BACKGROUND:Chlamydiaceae are a family of obligate intracellular pathogens causing a wide range of diseases in animals and humans, and facing unique evolutionary constraints not encountered by free-living prokaryotes. To investigate genomic aspects of infection, virulence and host preference we have sequenced Chlamydia psittaci, the pathogenic agent of ornithosis. RESULTS:A comparison of the genome of the avian Chlamydia psittaci isolate 6BC with the genomes of other chlamydial species, C. trachomatis, C. muridarum, C. pneumoniae, C. abortus, C. felis and C. caviae, revealed a high level of sequence conservation and synteny across taxa, with the major exception of the human pathogen C. trachomatis. Important differences manifest in the polymorphic membrane protein family specific for the Chlamydiae and in the highly variable chlamydial plasticity zone. We identified a number of psittaci-specific polymorphic membrane proteins of the G family that may be related to differences in host-range and/or virulence as compared to closely related Chlamydiaceae. We calculated non-synonymous to synonymous substitution rate ratios for pairs of orthologous genes to identify putative targets of adaptive evolution and predicted type III secreted effector proteins. CONCLUSIONS:This study is the first detailed analysis of the Chlamydia psittaci genome sequence. It provides insights in the genome architecture of C. psittaci and proposes a number of novel candidate genes mostly of yet unknown function that may be important for pathogen-host interactions.
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Project description:Chlamydia psittaci 6BC/83 Genome sequencing
| PRJNA186628 | ENA
Project description:Chlamydia psittaci primarily infects birds, but zoonotic transmission occurs in people in close contact with infected birds. The clinical outcome ranges from inapparent disease to pneumonia. Here we report the genome sequences of all 9 Chlamydia psittaci genotype reference strains.
| S-EPMC3510619 | biostudies-literature
Project description:The fitness cost of a resistance determinant is the primary parameter that determines its frequency in vivo. As a model for analysis of the impact of drug resistance mutations on the intracellular life cycle of Chlamydia spp., we studied the growth of four genetically defined spectinomycin-resistant (Spc(r)) clonal variants of Chlamydia psittaci 6BC isolated in the plaque assay. The development of each variant was monitored over 46 h postinfection in the absence of drug, either in pure culture or in 1:1 competition with the parent strain. Spc(r) mutations in the 16S rRNA gene at positions 1191 and 1193 were associated with a marked impairment of C.psittaci biological fitness, and the bacteria were severely out-competed by the wild-type parent. In contrast, mutations at position 1192 had minor effects on the bacterial life cycle, allowing the resistant isolates to compete more efficiently with the wild-type strain. Thus, mutations with a wide range of fitness costs can be selected in the plaque assay, providing a new strategy for prediction and monitoring of the emergence of antibiotic resistance in chlamydiae. So far, drug resistance has not been a serious threat for the treatment of chlamydial infections. Tetracycline is an effective antichlamydial drug that targets 16S rRNA. Attempts to isolate spontaneous tetracycline-resistant mutants of C. psittaci 6BC revealed a frequency <3 x 10(-9). We suggest that the rarity of genotypic antibiotic resistance among chlamydial clinical isolates reflects the deleterious effects of such mutations on the fitness of these obligate intracellular bacteria in the host.
| S-EPMC1280162 | biostudies-literature
Project description:Azithromycin is a major drug used in the treatment and prophylaxis of chlamydial infections. Spontaneous azithromycin-resistant mutants of Chlamydia psittaci 6BC were isolated in vitro in the plaque assay at a frequency of about 10(-8). Isogenic clonal variants with A(2058)C, A(2059)G, or A(2059)C mutations in the unique 23S rRNA gene (Escherichia coli numbering system) displayed MICs for multiple macrolides (i.e., azithromycin, erythromycin, josamycin, and spiramycin) at least 100 times higher than those of the parent strain and were also more resistant to the lincosamide clindamycin. Chlamydia trachomatis L2 variants with a Gln-to-Lys substitution in ribosomal protein L4 at position 66 (E. coli numbering system), conferring an eightfold decrease in azithromycin and erythromycin sensitivities and a fourfold decrease in josamycin and spiramycin sensitivities, were isolated following serial passage in subinhibitory concentrations of azithromycin. Each mutation was stably maintained in the absence of selection but severely affected chlamydial infectivity, as determined by monitoring the development of each isolate over 46 h in the absence of selection, in pure culture or in 1:1 competition with the isogenic parent. Data in this study support the hypothesis that the mechanisms which confer high-level macrolide resistance in chlamydiae carry a prohibitive physiological cost and may thus limit the emergence of highly resistant clones of these important pathogens in vivo.
| S-EPMC2167982 | biostudies-literature
Project description:The envelopes of elementary bodies of Chlamydia spp. consist largely of disulfide-cross-linked major outer membrane protein (MOMP) and two cysteine-rich proteins (CRPs). The MOMP gene of Chlamydia psittaci 6BC has been sequenced previously, and the genes encoding the small and large CRPs from this strain were cloned and sequenced in this study. The CRP genes were found to be tandemly arranged on the chlamydial chromosome but could be independently expressed in Escherichia coli. The deduced 87-amino-acid sequence of the small-CRP gene (envA) contains 15 cysteine residues, a potential signal peptide, and a potential signal peptidase II-lipid modification site. Hydropathy plot and conformation analysis of the small-CRP amino acid sequence indicated that the protein was unlikely to be associated with a membrane. However, the small CRP was specifically labeled in host cells incubated with [3H]palmitic acid and may therefore be associated with a membrane through a covalently attached lipid portion of the molecule. The deduced 557-amino-acid sequence of the large-CRP gene (envB) contains 37 cysteine residues and a single putative signal peptidase I cleavage site. In one recombinant clone the large CRP appeared to be posttranslationally cleaved at two sites, forming a doublet in a manner similar to the large-CRP doublet made in native C. psittaci 6BC. Comparison of the deduced amino acid sequences of the CRPs from chlamydial strains indicated that the small CRP is moderately conserved, with 54% identity between C. psittaci 6BC and Chlamydia trachomatis, and the large CRP is highly conserved, with 71% identity between C. psittaci and C. trachomatis and 85% identity between C. psittaci 6BC and Chlamydia pneumoniae. The positions of the cysteine residues in both CRPs are highly conserved in Chlamydia spp. From the number of cysteine residues in the MOMP and the CRPs and the relative incorporation of [35S]cysteine into these proteins, it was calculated that the molar ratio of C. psittaci 6BC elementary body envelope proteins is about one large-CRP molecule to two small-CRP molecules to five MOMP molecules.
| S-EPMC208014 | biostudies-other