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  • 1
    Electronic Resource
    Electronic Resource
    Primary structure of the peptidoglycan-derived tracheal cytotoxin of Bordetella pertussis (1989)
    s.l. : American Chemical Society
    Biochemistry 28 (1989), S. 1744-1749 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00430a048
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  • 2
    Electronic Resource
    Electronic Resource
    Histoplasma acquisition of calcium and expression of CBP1 during intracellular parasitism (1998)
    Oxford BSL : Blackwell Science Ltd, UK
    Molecular microbiology 27 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A highly adapted parasite of macrophages, the yeast phase of Histoplasma capsulatum, survives and proliferates within phagolysosomes, while the mycelial phase exists only as a saprophyte in the soil. We have shown previously that these two phases of Histoplasma differ in their calcium requirements for growth and in the production of a released calcium-binding protein (CBP). Cloning and sequencing the CBP1 gene revealed two introns, a putative signal peptide and potential calcium-binding sites. We also evaluated CBP1 expression by reverse transcription–polymerase chain reaction (RT–PCR) of yeasts grown in broth culture and within two host cell types, a macrophage-like cell line and respiratory epithelial cells. H. capsulatum yeasts expressed CBP1 in all of these settings. Splenocytes from mice immunized with H. capsulatum yeasts responded to purified CBP in proliferation assays, providing evidence for the production of CBP during the infection of mammalian hosts. In addition, after H. capsulatum yeasts were subjected to a calcium-free shock, exogenously added CBP allowed yeasts to incorporate more calcium than yeasts incubated without added CBP. These results suggest that CBP may function to provide yeasts with calcium when they are in a low-calcium environment, such as the phagolysosomal compartment within macrophages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00697.x
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  • 3
    Electronic Resource
    Electronic Resource
    Four genes are required for the system II cytochrome c biogenesis pathway in Bordetella pertussis, a unique bacterial model (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 38 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Unlike other cytochromes, c-type cytochromes have two covalent bonds formed between the two vinyl groups of haem and two cysteines of the protein. This haem ligation requires specific assembly proteins in prokaryotes or eukaryotic mitochondria and chloroplasts. Here, it is shown that Bordetella pertussis is an excellent bacterial model for the widespread system II cytochrome c synthesis pathway. Mutations in four different genes (ccsA, ccsB, ccsX and dipZ) result in B. pertussis strains unable to synthesize any of at least seven c-type cytochromes. Using a cytochrome c4:alkaline phosphatase fusion protein as a bifunctional reporter, it was demonstrated that the B. pertussis wild-type and mutant strains secrete an active alkaline phosphatase fusion protein. However, unlike the wild type, all four mutants are unable to attach haem covalently, resulting in a degraded N-terminal apocytochrome c4 component. Thus, apocytochrome c secretion is normal in each of the four mutants, but all are defective in a periplasmic assembly step (or export of haem). CcsX is related to thioredoxins, which possess a conserved CysXxxXxxCys motif. Using phoA gene fusions as reporters, CcsX was proven to be a periplasmic thioredoxin-like protein. Both the B. pertussis dipZ (i.e. dsbD) and ccsX mutants are corrected for their assembly defects by the thiol-reducing compounds, dithiothreitol and 2-mercaptoethanesulphonic acid. These results indicate that DipZ and CcsX are required for the periplasmic reduction of the cysteines of apocytochromes c before ligation. In contrast, the ccsA and ccsB mutants are not corrected by exogenous reducing agents, suggesting that CcsA and CcsB are required for the haem ligation step itself in the periplasm (or export of haem to the periplasm). Related to this suggestion, the topology of CcsB was determined experimentally, demonstrating that CcsB has four transmembrane domains and a large 435-amino-acid periplasmic region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02174.x
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  • 4
    Electronic Resource
    Electronic Resource
    In vivo generation of linear plasmids with addition of telomeric sequences by Histoplasma capsulatum (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 6 (1992), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Histoplasma capsulatum is a dimorphic pathogenic fungus that is a major cause of respiratory and systemic mycosis. We previously developed a transformation system for Histoplasma and demonstrated chromosomal integration of transforming plasmid sequences. In this study, we describe another Histoplasma mechanism for maintaining transforming DNA i.e. the generation of modified, multicopy linear plasmids carrying DNA from the transforming Escherichia coli plasmid. Under selective conditions, these linear plasmids were stable and capable of retransforming Histoplasma without further modification. In vivo modification of the transforming DNA included duplication of plasmid sequence and telomeric addition at the termini of linear DNA. Apparently Histoplasma telomerase, like that of other organisms such as humans and Tetrahymena, is able to act on non-telomeric substrates. The terminus of a Histoplasma linear plasmid was cloned and shown to contain multiple repeats of GGGTTA, the telomeric repeat unit also found in vertebrates, trypanosomes, and slime moulds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1992.tb01796.x
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  • 5
    Electronic Resource
    Electronic Resource
    Tracheal cytotoxin structural requirements for respiratory epithelial damage in pertussis (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 16 (1995), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The respiratory epithelial pathology of pertussis (whooping cough) can be reproduced by tracheal cyto-toxin (TCT), a disaccharide-tetrapeptide released by Bordetella pertussis. TCT is a muramyl peptide, a class of peptidoglycan-derived compounds which have many biological activities including adjuvanticity, somnogenicity, pyrogenicity, and cytotoxicity. The structural requirements for muramyl peptides to produce some of these biological effects have been partially characterized. Using in vitro assays with respiratory epithelial cells and tissue, we have previously determined that the disaccharide moiety of TCT is not involved in toxicity and that the side-chain functional groups of diaminopimelic acid (A2pm) are crucial for toxicity. In this study, we determine the importance of every amino acid, functional group and chiral centre in the peptide portion of TCT. Although lactyl tetrapeptides are the most toxic of the TCT fragments, producing dose-response curves identical to TCT, the smallest analogues of TCT which are active in our assay are of the form X-γ-(d)-Glu-meso-A2pm, where X may be an amino acid or a blocking group. Within this active substructure, main-chain chirality and all functional groups are essential for toxicity. This definition of the core region of TCT indicates that the TCT interaction site is unlike almost all other muramyl peptide interaction sites for which structure-activity data are available.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1995.tb02434.x
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  • 6
    Electronic Resource
    Electronic Resource
    An isogenic haemolysin-deficient mutant of Haemophilus ducreyi lacks the ability to produce cytopathic effects on human foreskin fibroblasts (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 21 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The haemolysin of Haemophilus ducreyi is the newest member of the Proteus/Serratia family of pore-forming toxins. In order to assess the role of the haemolysin in virulence, we constructed an isogenic haemolysin-deficient mutant of H. ducreyi strain 35000. This strain, designated 35000-3, lacks detectable haemolytic activity. We tested H. ducreyi strains 35000 and 35000-3 for their cytopathic activity against human foreskin fibroblasts (HFFs). We observed strong cytopathic activity when strain 35000 was co-cultured with HFFs. In contrast, cytopathic activity was not observed when strain 35000-3 was co-cultured with HFF cells. We also analysed the isogenic pair of H. ducreyi strains for cytopathic activity against HeLa cells and the keratinocyte cell line HaCaT. Strains 35000 and 35000-3 were strongly cytotoxic when co-cultured with HeLa cells. HaCaT monolayers were slightly damaged by cocultivation with strain 35000-3 but this damage was much less than that observed when HaCaT cells were cocultured with strain 35000. These results indicate that the H. ducreyi haemolysin is responsible for the previously observed cytotoxic activity against HFF cells and is partially responsible for the activity observed with HaCaT cells. The haemolysin, however, is not responsible for the activity observed with HeLa cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.00615.x
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  • 7
    Electronic Resource
    Electronic Resource
    RNA interference in Histoplasma capsulatum demonstrates a role for α-(1,3)-glucan in virulence (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 53 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Histoplasma capsulatum is a fungal pathogen that causes respiratory and systemic disease by proliferating within macrophages. While much is known about histoplasmosis, only a single virulence factor has been defined, in part because of the inefficiency of Histoplasma reverse genetics. As an alternative to allelic replacement, we have developed a telomeric plasmid-based system for silencing gene expression in Histoplasma by RNA interference (RNAi). Episomal expression of long RNAs that form stem–loop structures triggered gene silencing. To test the effectiveness of RNAi in Histoplasma, we depleted expression of a gfp transgene as well as two endogenous genes, ADE2 and URA5, and showed significant reductions in corresponding gene function. Silencing was target gene specific, stable during macrophage infection and reversible. We used RNAi targeting AGS1 (encoding α-(1,3)-glucan synthase) to deplete levels of α-(1,3)-glucan, a cell wall polysaccharide. Loss of α-(1,3)-glucan by RNAi yielded phenotypes indistinguishable from an AGS1 deletion: attenuation of the ability to kill macrophages and colonize murine lungs. This demonstrates for the first time that α-(1,3)-glucan is an important contributor to Histoplasma virulence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04131.x
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  • 8
    Electronic Resource
    Electronic Resource
    Selection and characterization of ura5 mutants of Histoplasma capsulatum (1988)
    Springer
    Molecular genetics and genomics 214 (1988), S. 348-352 
    Details
    ISSN: 1617-4623
    Keywords: Histoplasma capsulatum ; Fungus ; Orotidine-5′-monophosphate pyrophosphorylase ; Uracil ; Auxotroph
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The combined use of non-aggregating Histoplasma capsulatum strains and a defined medium which allows quantitative plating of the yeast phase has allowed us to select 5-fluoroorotic acid (5-FOA)-resistant mutants of this dimorphic fungus. Approximately two-thirds of the 5-FOA-resistant strains were auxotrophic for uracil; all were deficient in orotidine-5′-monophosphate pyrophosphorylase (OMPpase) activity. One class of OMPpase mutant (α), which retained a low level of OMPpase activity, was auxotrophic in the yeast phase (37°C) but grew slowly in the mycelial phase (25°C) without exogenous uracil. This phenotype was not due to a temperature-sensitive OMPpase activity. Both wild-type and α mutants had a higher OMPpase activity in the mycelial phase than the yeast phase; this increased activity may be sufficient to allow mycelial growth of α mutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337734
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  • 9
    Electronic Resource
    Electronic Resource
    Development of a genetic transformation system for Histoplasma capsulatum: Complementation of uracil auxotrophy (1990)
    Springer
    Molecular genetics and genomics 221 (1990), S. 358-362 
    Details
    ISSN: 1617-4623
    Keywords: Histoplasma capsulatum ; Fungus ; Transformation ; Uracil ; Auxotroph
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have developed a simple and efficient transformation system for the dimorphic fungus Histoplasma capsulatum. Mutants of H. capsulatum defective in orotidine-5′-monophosphate pyrophosphorylase were transformed to prototrophy by the cloned URA5 gene of the filamentous fungus Podospora anserina. Abortive and mitotically stable transformants were obtained. The stable transformants had integrated copies of the plasmid, some in tandem head-to-tail orientation. Free plasmid identical to the transforming plasmid was present in some of the transformants. We obtained a transformation efficiency of up to 30 transformants/μg DNA for plasmid pPAura5-1 (9.2 kb). pPW2001, a smaller plasmid (4.7 kb) derived from pPAura5-1, transformed H. capsulatum more efficiently (up to 155 transformants/gm DNA).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00259400
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