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Berlin Brandenburg

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  • 1
    Language: English
    In: Journal of bacteriology, October 2010, Vol.192(19), pp.5093-102
    Description: Chlamydiae are a group of obligate intracellular bacteria comprising several important human pathogens. Inside the eukaryotic cell, chlamydiae remain within a host-derived vesicular compartment, termed the inclusion. They modify the inclusion membrane through insertion of unique proteins, which are involved in interaction with and manipulation of the host cell. Among chlamydiae, inclusion membrane proteins have been exclusively found in members of the family Chlamydiaceae, which predominantly infect mammalian and avian hosts. Here, the presence of inclusion membrane proteins in Protochlamydia amoebophila UWE25, a chlamydial endosymbiont of free-living amoebae, is reported. A genome-wide screening for secondary structure motifs resulted in the identification of 23 putative inclusion membrane proteins for this organism. Immunofluorescence analysis demonstrated that five of these proteins were expressed, and four of them could be localized to a halo surrounding the intracellular bacteria. Colocalization studies showed an almost complete overlap of the signals obtained for the four putative inclusion membrane proteins, and immuno-transmission electron microscopy unambiguously demonstrated their location in the inclusion membrane. The presence of inclusion membrane proteins (designated IncA, IncQ, IncR, and IncS) in P. amoebophila shows that this strategy for host cell interaction is conserved among the chlamydiae and is used by chlamydial symbionts and pathogens alike.
    Keywords: Bacterial Proteins -- Metabolism ; Chlamydia -- Growth & Development ; Membrane Proteins -- Metabolism
    ISSN: 00219193
    E-ISSN: 1098-5530
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  • 2
    In: The Journal of Infectious Diseases, 2017, Vol. 215(11), pp.1657-1665
    Description: Genome sequence analysis of clinical samples demonstrated that identical or nearly identical Chlamydia trachomatis strains can be isolated from individual patients for up to 5 years. These data provide evidence for chlamydial persistence, even when patients are treated with antibiotics.
    Keywords: 〈Kwd〉 〈Italic Toggle="Yes"〉Chlamydia Trachomatis〈/Italic〉 〈/Kwd〉 ; Genomics ; Persistent Infection ; Sexually Transmitted Infection.
    ISSN: 0022-1899
    E-ISSN: 1537-6613
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  • 3
    Language: English
    In: The Journal of experimental medicine, 24 October 2011, Vol.208(11), pp.2159-62
    Description: Chlamydial plasmids are small, highly conserved, nonconjugative, and nonintegrative DNA molecules that are nearly ubiquitous in many chlamydial species, including Chlamydia trachomatis. There has been significant recent progress in understanding chlamydial plasmid participation in host-microbe interactions, disease, and immune responses. Work in mouse model systems and, very recently, in nonhuman primates demonstrates that plasmid-deficient chlamydial strains function as live attenuated vaccines against genital and ocular infections. Collectively, these studies open new avenues of research into developing vaccines against trachoma and sexually transmitted chlamydial infections.
    Keywords: DNA, Bacterial ; Chlamydia Trachomatis -- Genetics ; Plasmids -- Genetics
    ISSN: 00221007
    E-ISSN: 1540-9538
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  • 4
    Language: English
    In: Journal of Bacteriology, May, 2010, Vol.192(9-10), p.2645(2)
    Description: In syphilis research, the Nichols strain of Treponema pallidum, isolated in 1912, has been the most widely studied. Recently, important differences among T. pallidum strains emerged; therefore, we sequenced and annotated the Chicago strain genome to facilitate and encourage the use of this strain in studying the pathogenesis of syphilis. doi: 10.1128/JB.00159-10
    Keywords: Treponema Pallidum -- Genetic Aspects ; Syphilis -- Research ; Bacterial Genetics -- Research
    ISSN: 0021-9193
    E-ISSN: 10985530
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  • 5
    Language: English
    In: Chlamydial Infection: A Clinical and Public Health Perspective, 2013, Vol.7, p.61-77
    Description: Abstract Next generation sequencing approaches have led to completion of several dozen chlamydial genome sequences, most of which are from Chlamydia trachomatis . Analysis of these genomes has shown that chlamydiae, like other obligate intracellular bacteria, have a much reduced genome structure that implies dependence on the host for much metabolic capability. Certain groups of genes, including those encoding inclusion membrane proteins and the family of Pmp proteins, have been significantly expanded against this general reductive evolutionary strategy. Pregenomic and postgenomic sequence analysis of C. trachomatis has led to considerable understanding of nucleotide polymorphisms, insertions and deletions that are associated with certain clinical presentations. Future research will address chlamydial genome structure in the context of the system in which they live, and will include data on the host microbiome and host genetic background. We anticipate that integrating these areas of research will lead to significant progress in our understanding of the nature of chlamydial infection and disease. Copyright © 2013 S. Karger AG, Basel
    ISBN: 978-3-318-02398-5
    ISSN: 1660-1890
    E-ISSN: 1662-3819
    Source: Karger Book Series
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  • 6
    Language: English
    In: Microbiology (Reading, England), October 2013, Vol.159(Pt 10), pp.2109-17
    Description: A culture-independent genome sequencing approach was developed and used to examine genomic variability in Chlamydia trachomatis-positive specimens that were collected from patients in the Seattle, WA, USA, area. The procedure is based on an immunomagnetic separation approach with chlamydial LPS-specific mAbs, followed by DNA purification and total DNA amplification, and subsequent Illumina-based sequence analysis. Quality of genome sequencing was independent of the total number of inclusion-forming units determined for the sample and the amount of non-chlamydial DNA in the Illumina libraries. A geographically and temporally linked clade of isolates was identified with evidence of several different regions of recombination and variable ompA sequence types, suggesting that recombination is common within outbreaks. Culture-independent sequence analysis revealed a linkage pattern at two nucleotide positions that was unique to the genomes of isolates from patients, but not in C. trachomatis recombinants generated in vitro. These data demonstrated that culture-independent sequence analysis can be used to rapidly and inexpensively collect genome data from patients infected by C. trachomatis, and that this approach can be used to examine genomic variation within this species.
    Keywords: Genetic Variation ; Recombination, Genetic ; Bacteriological Techniques -- Methods ; Chlamydia Infections -- Microbiology ; Chlamydia Trachomatis -- Genetics ; Genitalia -- Microbiology
    ISSN: 13500872
    E-ISSN: 1465-2080
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  • 7
    Language: English
    In: Journal of bacteriology, 01 August 2016, Vol.198(15), pp.2131-9
    Description: Intracellular bacterial pathogens in the family Chlamydiaceae are causes of human blindness, sexually transmitted disease, and pneumonia. Genetic dissection of the mechanisms of chlamydial pathogenicity has been hindered by multiple limitations, including the inability to inactivate genes that would prevent the production of elementary bodies. Many genes are also Chlamydia-specific genes, and chlamydial genomes have undergone extensive reductive evolution, so functions often cannot be inferred from homologs in other organisms. Conditional mutants have been used to study essential genes of many microorganisms, so we screened a library of 4,184 ethyl methanesulfonate-mutagenized Chlamydia trachomatis isolates for temperature-sensitive (TS) mutants that developed normally at physiological temperature (37°C) but not at nonphysiological temperatures. Heat-sensitive TS mutants were identified at a high frequency, while cold-sensitive mutants were less common. Twelve TS mutants were mapped using a novel markerless recombination approach, PCR, and genome sequencing. TS alleles of genes that play essential roles in other bacteria and chlamydia-specific open reading frames (ORFs) of unknown function were identified. Temperature-shift assays determined that phenotypes of the mutants manifested at distinct points in the developmental cycle. Genome sequencing of a larger population of TS mutants also revealed that the screen had not reached saturation. In summary, we describe the first approach for studying essential chlamydial genes and broadly applicable strategies for genetic mapping in Chlamydia spp. and mutants that both define checkpoints and provide insights into the biology of the chlamydial developmental cycle. Study of the pathogenesis of Chlamydia spp. has historically been hampered by a lack of genetic tools. Although there has been recent progress in chlamydial genetics, the existing approaches have limitations for the study of the genes that mediate growth of these organisms in cell culture. We used a genetic screen to identify conditional Chlamydia mutants and then mapped these alleles using a broadly applicable recombination strategy. Phenotypes of the mutants provide fundamental insights into unexplored areas of chlamydial pathogenesis and intracellular biology. Finally, the reagents and approaches we describe are powerful resources for the investigation of these organisms.
    Keywords: Recombination, Genetic ; Temperature ; Chlamydia Trachomatis -- Physiology
    ISSN: 00219193
    E-ISSN: 1098-5530
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  • 8
    In: The Journal of Bacteriology, 2010, Vol. 192(10), p.2645
    Description: In syphilis research, the Nichols strain of Treponema pallidum, isolated in 1912, has been the most widely studied. Recently, important differences among T. pallidum strains emerged; therefore, we sequenced and annotated the Chicago strain genome to facilitate and encourage the use of this strain in studying the pathogenesis of syphilis.
    Keywords: Biology;
    ISSN: 0021-9193
    ISSN: 00219193
    E-ISSN: 10985530
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  • 9
    Language: English
    In: Infection and immunity, October 2016, Vol.84(10), pp.2791-801
    Description: Chlamydia trachomatis can enter a viable but nonculturable state in vitro termed persistence. A common feature of C. trachomatis persistence models is that reticulate bodies fail to divide and make few infectious progeny until the persistence-inducing stressor is removed. One model of persistence that has relevance to human disease involves tryptophan limitation mediated by the host enzyme indoleamine 2,3-dioxygenase, which converts l-tryptophan to N-formylkynurenine. Genital C. trachomatis strains can counter tryptophan limitation because they encode a tryptophan-synthesizing enzyme. Tryptophan synthase is the only enzyme that has been confirmed to play a role in interferon gamma (IFN-γ)-induced persistence, although profound changes in chlamydial physiology and gene expression occur in the presence of persistence-inducing stressors. Thus, we screened a population of mutagenized C. trachomatis strains for mutants that failed to reactivate from IFN-γ-induced persistence. Six mutants were identified, and the mutations linked to the persistence phenotype in three of these were successfully mapped. One mutant had a missense mutation in tryptophan synthase; however, this mutant behaved differently from previously described synthase null mutants. Two hypothetical genes of unknown function, ctl0225 and ctl0694, were also identified and may be involved in amino acid transport and DNA damage repair, respectively. Our results indicate that C. trachomatis utilizes functionally diverse genes to mediate survival during and reactivation from persistence in HeLa cells.
    Keywords: Chlamydia Trachomatis -- Genetics ; Interferon-Gamma -- Physiology ; Tryptophan Synthase -- Genetics
    ISSN: 00199567
    E-ISSN: 1098-5522
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  • 10
    Language: English
    In: Infection and immunity, February 2016, Vol.84(2), pp.480-90
    Description: The direct major histocompatibility complex (MHC) class I antigen presentation pathway ensures intracellular peptides are displayed at the cellular surface for recognition of infected or transformed cells by CD8(+) cytotoxic T lymphocytes. Chlamydia spp. are obligate intracellular bacteria and, as such, should be targeted by CD8(+) T cells. It is likely that Chlamydia spp. have evolved mechanisms to avoid the CD8(+) killer T cell responses by interfering with MHC class I antigen presentation. Using a model system of self-peptide presentation which allows for posttranslational control of the model protein's stability, we tested the ability of various Chlamydia species to alter direct MHC class I antigen presentation. Infection of the JY lymphoblastoid cell line limited the accumulation of a model host protein and increased presentation of the model-protein-derived peptides. Enhanced self-peptide presentation was detected only when presentation was restricted to defective ribosomal products, or DRiPs, and total MHC class I levels remained unaltered. Skewed antigen presentation was dependent on a bacterial synthesized component, as evidenced by reversal of the observed phenotype upon preventing bacterial transcription, translation, and the inhibition of bacterial lipooligosaccharide synthesis. These data suggest that Chlamydia spp. have evolved to alter the host antigen presentation machinery to favor presentation of defective and rapidly degraded forms of self-antigen, possibly as a mechanism to diminish the presentation of peptides derived from bacterial proteins.
    Keywords: Antigen Presentation ; Host-Pathogen Interactions ; Autoantigens -- Immunology ; Chlamydia Trachomatis -- Immunology ; Histocompatibility Antigens Class I -- Immunology
    ISSN: 00199567
    E-ISSN: 1098-5522
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