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Berlin Brandenburg

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  • 1
    Language: English
    In: Infection and immunity, July 2018, Vol.86(7)
    Description: Some members of the genus , including the human pathogen , infect multiple tissues, including the genital and gastrointestinal (GI) tracts. However, it is unknown if bacterial targeting to these sites is mediated by multifunctional or distinct chlamydial factors. We previously showed that disruption of individual large clostridial toxin homologs encoded within the plasticity zone were not critical for murine genital tract infection. Here, we assessed whether cytotoxin genes contribute to GI tropism. Infectivity and shedding of wild-type (WT) and three mutants containing nonsense mutations in different cytotoxin genes, , , and , were compared in mouse genital and GI infection models. One mutant, which had a nonsense mutation in , was highly attenuated for GI infection and had a GI 50% infectious dose (ID) that was 1,000 times greater than that of the WT. GI inoculation with this mutant failed to elicit anti-chlamydial antibodies or to protect against subsequent genital tract infection. Genome sequencing of the mutant revealed additional chromosomal mutations, and phenotyping of additional mutants suggested that the GI attenuation might be linked to a nonsense mutation in The molecular mechanism underlying this dramatic difference in tissue-tropic virulence is not fully understood. However, isolation of these mutants demonstrates that distinct chlamydial chromosomal factors mediate chlamydial tissue tropism and provides a basis for vaccine initiatives to isolate chlamydia strains that are attenuated for genital infection but retain the ability to colonize the GI tract and elicit protective immune responses.
    Keywords: Chlamydia ; Gastrointestinal Infection ; Genital Tract Immunity ; Intracellular Bacteria ; Intracellular Pathogen ; Sexually Transmitted Diseases ; Tropism ; Chlamydia Infections -- Etiology ; Chlamydia Muridarum -- Pathogenicity ; Chromosomes -- Physiology ; Gastrointestinal Diseases -- Etiology ; Reproductive Tract Infections -- Etiology
    ISSN: 00199567
    E-ISSN: 1098-5522
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  • 2
    Language: English
    In: PLoS ONE, 01 January 2014, Vol.9(10), p.e109677
    Description: Relationships between host and microbial diversity have important ecological and applied implications. Theory predicts that these relationships will depend on the spatio-temporal scale of the analysis and the niche breadth of the organisms in question, but representative data on host-microbial community assemblage in nature is lacking. We employed a natural gradient of rodent species richness and quantified bacterial communities in rodent blood at several hierarchical spatial scales to test the hypothesis that associations between host and microbial species diversity will be positive in communities dominated by organisms with broad niches sampled at large scales. Following pyrosequencing of rodent blood samples, bacterial communities were found to be comprised primarily of broad niche lineages. These communities exhibited positive correlations between host diversity, microbial diversity and the likelihood for rare pathogens at the regional scale but not at finer scales. These findings demonstrate how microbial diversity is affected by host diversity at different spatial scales and suggest that the relationships between host diversity and overall disease risk are not always negative, as the dilution hypothesis predicts.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 3
    In: The ISME Journal, 2015
    Description: Vector-borne microbes are subject to the ecological constraints of two distinct microenvironments: that in the arthropod vector and that in the blood of its vertebrate host. Because the structure of bacterial communities in these two microenvironments may substantially affect the abundance of vector-borne microbes, it is important to understand the relationship between bacterial communities in both microenvironments and the determinants that shape them. We used pyrosequencing analyses to compare the structure of bacterial communities in Synosternus cleopatrae fleas and in the blood of their Gerbillus andersoni hosts. We also monitored the interindividual and seasonal variability in these bacterial communities by sampling the same individual wild rodents during the spring and again during the summer. We show that the bacterial communities in each sample type (blood, female flea or male flea) had a similar phylotype composition among host individuals, but exhibited seasonal variability that was not directly associated with host characteristics. The structure of bacterial communities in male fleas and in the blood of their rodent hosts was remarkably similar and was dominated by flea-borne Bartonella and Mycoplasma phylotypes. A lower abundance of flea-borne bacteria and the presence of Wolbachia phylotypes distinguished bacterial communities in female fleas from those in male fleas and in rodent blood. These results suggest that the overall abundance of a certain vector-borne microbe is more likely to be determined by the abundance of endosymbiotic bacteria in the vector, abundance of other vector-borne microbes co-occurring in the vector and in the host blood and by seasonal changes, than by host characteristics.
    Keywords: Biology;
    ISSN: 1751-7362
    E-ISSN: 17517370
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  • 4
    Language: English
    In: Infection and immunity, July 2015, Vol.83(7), pp.2870-81
    Description: Pathogenically diverse Chlamydia spp. can have surprisingly similar genomes. Chlamydia trachomatis isolates that cause trachoma, sexually transmitted genital tract infections (chlamydia), and invasive lymphogranuloma venereum (LGV) and the murine strain Chlamydia muridarum share 99% of their gene content. A region of high genomic diversity between Chlamydia spp. termed the plasticity zone (PZ) may encode niche-specific virulence determinants that dictate pathogenic diversity. We hypothesized that PZ genes might mediate the greater virulence and gamma interferon (IFN-γ) resistance of C. muridarum compared to C. trachomatis in the murine genital tract. To test this hypothesis, we isolated and characterized a series of C. muridarum PZ nonsense mutants. Strains with nonsense mutations in chlamydial cytotoxins, guaBA-add, and a phospholipase D homolog developed normally in cell culture. Two of the cytotoxin mutants were less cytotoxic than the wild type, suggesting that the cytotoxins may be functional. However, none of the PZ nonsense mutants exhibited increased IFN-γ sensitivity in cell culture or were profoundly attenuated in a murine genital tract infection model. Our results suggest that C. muridarum PZ genes are transcribed--and some may produce functional proteins--but are dispensable for infection of the murine genital tract.
    Keywords: Genome, Bacterial ; Chlamydia Infections -- Microbiology ; Chlamydia Muridarum -- Genetics ; Virulence Factors -- Genetics
    ISSN: 00199567
    E-ISSN: 1098-5522
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  • 5
    In: Evolution & Development, July 2013, Vol.15(4), pp.243-256
    Description: Byline: Elizabeth C. Raff, Mary E. Andrews, F. Rudolf Turner, Evelyn Toh, David E. Nelson, Rudolf A. Raff SUMMARY Fossils of soft tissues provide important records of early animals and embryos, and there is substantial evidence for a role for microbes in soft tissue fossilization. We are investigating the initial events in interactions of bacteria with freshly dead tissue, using marine embryos as a model system. We previously found that microbial invasion can stabilize embryo tissue that would otherwise disintegrate in hours or days by generating a bacterial pseudomorph, a three-dimensional biofilm that both replaces the tissue and replicates its morphology. In this study, we sampled seawater at different times and places near Sydney, Australia, and determined the range and frequency of different taphonomic outcomes. Although destruction was most common, bacteria in 35% of seawater samples yielded morphology-preserving biofilms. We could replicate the taphonomic pathways seen with seawater bacterial communities using single cultured strains of marine gammaproteobacteria. Each given species reproducibly generated a consistent taphonomic outcome and we identified species that yielded each of the distinct pathways produced by seawater bacterial communities. Once formed, bacterial pseudomorphs are stable for over a year and resist attack by other bacteria and destruction by proteases and other lytic enzymes. Competition studies showed that the initial action of a pseudomorphing strain can be blocked by a strain that destroys tissues. Thus embryo preservation in nature may depend on contingent interactions among bacterial species that determine if pseudomorphing occurs. We used Artemia nauplius larvae to show that bacterial biofilm replacement of tissue is not restricted to embryos, but is relevant for preservation of small multicellular organisms. We present a model for bacterial self-assembly of large-scale three-dimensional tissue pseudomorphs, based on small-scale interactions among individual bacterial cells to form local biofilms at structural boundaries within the tissue. Local biofilms then conjoin to generate the pseudomorph. Author Affiliation:
    Keywords: Seawater -- Protection And Preservation ; Seawater -- Analysis ; Fossilization -- Protection And Preservation ; Fossilization -- Analysis ; Bacteria -- Protection And Preservation ; Bacteria -- Analysis ; Pseudomorphs -- Protection And Preservation ; Pseudomorphs -- Analysis ; Embryonic Development -- Protection And Preservation ; Embryonic Development -- Analysis;
    ISSN: 1520-541X
    E-ISSN: 1525-142X
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  • 6
    In: The ISME Journal, 2012, Vol.7(1), p.221
    Description: Bacterial community composition in blood-sucking arthropods can shift dramatically across time and space. We used 16S rRNA gene amplification and pyrosequencing to investigate the relative impact of vertebrate host-related, arthropod-related and environmental factors on bacterial community composition in fleas and ticks collected from rodents in southern Indiana (USA). Bacterial community composition was largely affected by arthropod identity, but not by the rodent host or environmental conditions. Specifically, the arthropod group (fleas vs ticks) determined the community composition of bacteria, where bacterial communities of ticks were less diverse and more dependent on arthropod traits--especially tick species and life stage--than bacterial communities of fleas. Our data suggest that both arthropod life histories and the presence of arthropod-specific endosymbionts may mask the effects of the vertebrate host and its environment.
    Keywords: Biology;
    ISSN: 1751-7362
    E-ISSN: 17517370
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  • 7
    Language: English
    In: mBio, 09 April 2019, Vol.10(2)
    Description: Interferon-regulated immune defenses protect mammals from pathogenically diverse obligate intracellular bacterial pathogens of the genus Interferon gamma (IFN-γ) is especially important in controlling the virulence of species and thus impacts the modeling of human chlamydial infection and disease in mice. How IFN-γ contributes to cell-autonomous defenses against species and how these pathogens evade IFN-γ-mediated immunity in their natural hosts are not well understood. We conducted a genetic screen which identified 31 -ensitive (Igs) mutants of the mouse model pathogen Genetic suppressor analysis and lateral gene transfer were used to map the phenotype of one of these mutants, Igs4, to a missense mutation in a putative chlamydial inclusion membrane protein, TC0574. We observed the lytic destruction of Igs4-occupied inclusions and accompanying host cell death in response to IFN-γ priming or various proapoptotic stimuli. However, Igs4 was insensitive to IFN-γ-regulated cell-autonomous defenses previously implicated in anti- host defense in mice. Igs4 inclusion integrity was restored by caspase inhibitors, indicating that the IFN-γ-mediated destruction of Igs4 inclusions is dependent upon the function of caspases or related prodeath cysteine proteases. We further demonstrated that the Igs4 mutant is immune restricted in an IFN-γ-dependent manner in a mouse infection model, thereby implicating IFN-γ-mediated inclusion destruction and host cell death as potent host defense mechanisms to which wild-type is resistant. Overall, our results suggest that evolved resistance mechanisms to counter IFN-γ-elicited programmed cell death and the associated destruction of intravacuolar pathogens. Multiple obligatory intracellular bacteria in the genus are important pathogens. In humans, strains of cause trachoma, chlamydia, and lymphogranuloma venereum. These diseases are all associated with extended courses of infection and reinfection that likely reflect the ability of chlamydiae to evade various aspects of host immune responses. Interferon-stimulated genes, driven in part by the cytokine interferon gamma, restrict the host range of various species, but how these pathogens evade interferon-stimulated genes in their definitive host is poorly understood. Various species can inhibit death of their host cells and may have evolved this strategy to evade prodeath signals elicited by host immune responses. We present evidence that chlamydia-induced programmed cell death resistance evolved to counter interferon- and immune-mediated killing of -infected cells.
    Keywords: Chlamydia ; Host-Pathogen Interactions ; Interferon-Stimulated Genes ; Intracellular Pathogens ; Molecular Genetics ; Apoptosis ; Host-Pathogen Interactions ; Immune Evasion ; Immunity, Innate ; Chlamydia Muridarum -- Immunology ; Interferon-Gamma -- Metabolism
    ISSN: 21612129
    E-ISSN: 2150-7511
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  • 8
    Language: English
    In: The Journal of biological chemistry, 13 December 2013, Vol.288(50), pp.36040-51
    Description: NAT8L (N-acetyltransferase 8-like) catalyzes the formation of N-acetylaspartate (NAA) from acetyl-CoA and aspartate. In the brain, NAA delivers the acetate moiety for synthesis of acetyl-CoA that is further used for fatty acid generation. However, its function in other tissues remained elusive. Here, we show for the first time that Nat8l is highly expressed in adipose tissues and murine and human adipogenic cell lines and is localized in the mitochondria of brown adipocytes. Stable overexpression of Nat8l in immortalized brown adipogenic cells strongly increases glucose incorporation into neutral lipids, accompanied by increased lipolysis, indicating an accelerated lipid turnover. Additionally, mitochondrial mass and number as well as oxygen consumption are elevated upon Nat8l overexpression. Concordantly, expression levels of brown marker genes, such as Prdm16, Cidea, Pgc1α, Pparα, and particularly UCP1, are markedly elevated in these cells. Treatment with a PPARα antagonist indicates that the increase in UCP1 expression and oxygen consumption is PPARα-dependent. Nat8l knockdown in brown adipocytes has no impact on cellular triglyceride content, lipogenesis, or oxygen consumption, but lipolysis and brown marker gene expression are increased; the latter is also observed in BAT of Nat8l-KO mice. Interestingly, the expression of ATP-citrate lyase is increased in Nat8l-silenced adipocytes and BAT of Nat8l-KO mice, indicating a compensatory mechanism to sustain the acetyl-CoA pool once Nat8l levels are reduced. Taken together, our data show that Nat8l impacts on the brown adipogenic phenotype and suggests the existence of the NAT8L-driven NAA metabolism as a novel pathway to provide cytosolic acetyl-CoA for lipid synthesis in adipocytes.
    Keywords: Acetyl Coenzyme A ; Adipose Tissue Metabolism ; Aspartate ; Brown Adipocytes ; Energy Expenditure ; Fatty Acid Metabolism ; Lipid Metabolism ; N-Acetylaspartate ; N-Acetyltransferase 8-Like ; Energy Metabolism ; Lipid Metabolism ; Acetyltransferases -- Metabolism ; Adipocytes, Brown -- Metabolism
    E-ISSN: 1083-351X
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  • 9
    Language: English
    In: The Journal of Allergy and Clinical Immunology: In Practice, March 2018, Vol.6(2), pp.466-475.e1
    Description: There is mounting evidence that early introduction of allergenic food decreases the risk of food allergy development, especially in high-risk infants with eczema. However, there is a lack of data to suggest whether this association holds true in Asian populations. To investigate the relationship between the timing of introduction of allergenic foods and food allergy outcomes in infants in the Growing Up in Singapore Towards healthy Outcomes (GUSTO) study. The GUSTO cohort recruited 1152 mothers of Chinese, Malay, and Indian ethnicity who had singleton, naturally conceived pregnancies and followed their offspring prospectively. Information on demographic characteristics, child health, infant feeding practices, and a convincing history of IgE-mediated food allergy was obtained from interviewer-administered questionnaires at multiple time points. Corroborative skin prick tests to food allergens were performed at 18 and 36 months. Most of the infants were introduced to egg (49.6%), peanut (88.7%), and shellfish (90.2%) after age 10 months. Food allergy prevalence was, however, very low between age 12 and 48 months: egg, 0.35% to 1.8%; peanut allergy, 0.1% to 0.3%; and shellfish, 0.2% to 0.9%. There were no significant associations between the timing of introduction of allergenic foods and the development of food allergy, adjusted for confounders including breast-feeding and eczema. Food allergy rates in Singapore are low despite delayed introduction of allergenic foods. Early introduction of allergenic foods may thus not be necessary in populations in which overall food allergy prevalence is low, and thus infant feeding recommendations should be carefully tailored to individual populations.
    Keywords: Food Allergy ; Allergy Prevention ; Solids Introduction ; Allergenic Food Introduction ; Complementary Feeding ; Egg ; Milk ; Peanut ; Medicine
    ISSN: 2213-2198
    E-ISSN: 2213-2201
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  • 10
    In: Journal of Cellular and Molecular Medicine, July 2009, Vol.13(7), pp.1371-1380
    Description: Hepatocellular carcinoma (HCC) is the fifth most common malignancy worldwide and highly resistant to available chemotherapies. Mammalian target of rapamycin (mTOR) functions to regulate protein translation, angiogenesis and cell cycle progression in many cancers including HCC. In the present study, subcutaneous patient‐derived HCC xenografts were used to study the effects of an mTOR inhibitor, RAD001 (everolimus), on tumour growth, apoptosis and angiogenesis. We report that oral administration of RAD001 to mice bearing patient‐derived HCC xenografts resulted in a dose‐dependent inhibition of tumour growth. RAD001‐induced growth suppression was associated with inactivation of downstream targets of mTOR, reduction in VEGF expression and microvessel density, inhibition of cell proliferation, up‐regulation of p27 and down‐regulation of p21, Cdk‐6, Cdk‐2, Cdk‐4, cdc‐25C, cyclin B1 and c‐Myc. Our data indicate that the mTOR pathway plays an important role in angiogenesis, cell cycle progression and proliferation of liver cancer cells. Our study provides a strong rationale for clinical investigation of mTOR inhibitor RAD001 in patients with HCC.
    Keywords: Liver Cancer ; Angiogenesis ; Mtor ; Therapy
    ISSN: 1582-1838
    E-ISSN: 1582-4934
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